diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/Makefile.am | 43 | ||||
| -rw-r--r-- | doc/Makefile.in | 1557 | ||||
| -rw-r--r-- | doc/fdl-1.3.texi | 506 | ||||
| -rw-r--r-- | doc/gendocs_template | 96 | ||||
| -rw-r--r-- | doc/gpl-3.0.texi | 717 | ||||
| -rw-r--r-- | doc/m4.1 | 151 | ||||
| -rw-r--r-- | doc/m4.info | 134 | ||||
| -rw-r--r-- | doc/m4.info-1 | 7858 | ||||
| -rw-r--r-- | doc/m4.info-2 | 909 | ||||
| -rw-r--r-- | doc/m4.texinfo | 5308 | ||||
| -rw-r--r-- | doc/stamp-vti | 4 | ||||
| -rw-r--r-- | doc/version.texi | 4 |
12 files changed, 13759 insertions, 3528 deletions
diff --git a/doc/Makefile.am b/doc/Makefile.am index 92337649..9d3391d4 100644 --- a/doc/Makefile.am +++ b/doc/Makefile.am @@ -1,6 +1,6 @@ ## Makefile.am - template for generating Makefile via Automake ## -## Copyright (C) 2009, 2010 Free Software Foundation, Inc. +## Copyright (C) 2006-2011 Free Software Foundation, Inc. ## ## This file is part of GNU M4. ## @@ -16,29 +16,28 @@ ## ## You should have received a copy of the GNU General Public License ## along with this program. If not, see <http://www.gnu.org/licenses/>. +## +## This file written by Eric Blake <ebb9@byu.net> -MAINTAINERCLEANFILES = -EXTRA_DIST = -config_aux_dir = build-aux - -info_TEXINFOS = m4.texinfo -m4_TEXINFOS = regexprops-generic.texi fdl-1.3.texi gpl-3.0.texi -dist_man_MANS = $(srcdir)/m4.1 -EXTRA_DIST += gendocs_template -MAINTAINERCLEANFILES += gendocs_template -HELP2MAN = $(SHELL) $(top_srcdir)/$(config_aux_dir)/missing --run help2man +info_TEXINFOS = m4.texinfo +m4_TEXINFOS = fdl-1.3.texi gpl-3.0.texi +man_MANS = $(srcdir)/m4.1 +EXTRA_DIST = $(man_MANS) gendocs_template +MAINTAINERCLEANFILES = $(man_MANS) gendocs_template +SUFFIXES = .1 +HELP2MAN = $(SHELL) $(top_srcdir)/build-aux/missing --run help2man +# Depend on ../.version for version, m4.c for usage text. Do not depend on +# built m4 executable, since not everyone has help2man or perl. # Build the man page once in the srcdir, rather than in every VPATH build # dir, to match how automake builds info pages. This is safe for 'make # distcheck' since it is distributed pre-built. -$(srcdir)/m4.1: ../.version $(srcdir)/../src/main.c - @echo "Updating the \`man' page \`$@'"; \ - $(HELP2MAN) --name="macro processor" --source=FSF \ - --info-page=m4 --output=$@ ../src/m4$(EXEEXT) - -TAGS_FILES = $(infos_TEXINFOS) -TAGS_DEPENDENCIES = $(TAGS_FILES) -ETAGS_ARGS = --language=none --regex='/@node \([^,]*\)/\1/' $(TAGS_FILES) - -MAINTAINERCLEANFILES += $(dist_man_MANS) - +$(srcdir)/m4.1: $(top_srcdir)/.version $(top_srcdir)/src/m4.c + @if test -x ../src/m4$(EXEEXT) ; then \ + echo "Updating man page m4.1" ; \ + $(HELP2MAN) --name="macro processor" --source='$(PACKAGE_STRING)' \ + --info-page=m4 --output=$@ ../src/m4$(EXEEXT) ; \ + else \ + echo "WARNING: The \`man' page \`$@' cannot be updated yet."; \ + echo " Retry once the program executable is ready."; \ + fi diff --git a/doc/Makefile.in b/doc/Makefile.in new file mode 100644 index 00000000..25e44aa6 --- /dev/null +++ b/doc/Makefile.in @@ -0,0 +1,1557 @@ +# Makefile.in generated by automake 1.11.1 from Makefile.am. +# @configure_input@ + +# Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, +# 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, +# Inc. +# This Makefile.in is free software; the Free Software Foundation +# gives unlimited permission to copy and/or distribute it, +# with or without modifications, as long as this notice is preserved. + +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY, to the extent permitted by law; without +# even the implied warranty of MERCHANTABILITY or FITNESS FOR A +# PARTICULAR PURPOSE. + +@SET_MAKE@ +VPATH = @srcdir@ +pkgdatadir = $(datadir)/@PACKAGE@ +pkgincludedir = $(includedir)/@PACKAGE@ +pkglibdir = $(libdir)/@PACKAGE@ +am__cd = CDPATH="$${ZSH_VERSION+.}$(PATH_SEPARATOR)" && cd +install_sh_DATA = $(install_sh) -c -m 644 +install_sh_PROGRAM = $(install_sh) -c +install_sh_SCRIPT = $(install_sh) -c +INSTALL_HEADER = $(INSTALL_DATA) +transform = $(program_transform_name) +NORMAL_INSTALL = : +PRE_INSTALL = : +POST_INSTALL = : +NORMAL_UNINSTALL = : +PRE_UNINSTALL = : +POST_UNINSTALL = : +build_triplet = @build@ +host_triplet = @host@ +subdir = doc +DIST_COMMON = $(m4_TEXINFOS) $(srcdir)/Makefile.am \ + $(srcdir)/Makefile.in $(srcdir)/stamp-vti \ + $(srcdir)/version.texi +ACLOCAL_M4 = $(top_srcdir)/aclocal.m4 +am__aclocal_m4_deps = $(top_srcdir)/m4/00gnulib.m4 \ + $(top_srcdir)/m4/alloca.m4 $(top_srcdir)/m4/ansi-c++.m4 \ + $(top_srcdir)/m4/assert.m4 $(top_srcdir)/m4/autobuild.m4 \ + $(top_srcdir)/m4/btowc.m4 $(top_srcdir)/m4/c-stack.m4 \ + $(top_srcdir)/m4/canonicalize.m4 $(top_srcdir)/m4/cloexec.m4 \ + $(top_srcdir)/m4/close-stream.m4 $(top_srcdir)/m4/close.m4 \ + $(top_srcdir)/m4/closein.m4 $(top_srcdir)/m4/closeout.m4 \ + $(top_srcdir)/m4/codeset.m4 $(top_srcdir)/m4/config-h.m4 \ + $(top_srcdir)/m4/configmake.m4 $(top_srcdir)/m4/dirname.m4 \ + $(top_srcdir)/m4/double-slash-root.m4 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+GNULIB_FCLOSE = @GNULIB_FCLOSE@ +GNULIB_FCNTL = @GNULIB_FCNTL@ +GNULIB_FFLUSH = @GNULIB_FFLUSH@ +GNULIB_FLOOR = @GNULIB_FLOOR@ +GNULIB_FLOORF = @GNULIB_FLOORF@ +GNULIB_FLOORL = @GNULIB_FLOORL@ +GNULIB_FOPEN = @GNULIB_FOPEN@ +GNULIB_FPRINTF = @GNULIB_FPRINTF@ +GNULIB_FPRINTF_POSIX = @GNULIB_FPRINTF_POSIX@ +GNULIB_FPURGE = @GNULIB_FPURGE@ +GNULIB_FPUTC = @GNULIB_FPUTC@ +GNULIB_FPUTS = @GNULIB_FPUTS@ +GNULIB_FREOPEN = @GNULIB_FREOPEN@ +GNULIB_FREXP = @GNULIB_FREXP@ +GNULIB_FREXPL = @GNULIB_FREXPL@ +GNULIB_FSEEK = @GNULIB_FSEEK@ +GNULIB_FSEEKO = @GNULIB_FSEEKO@ +GNULIB_FSTATAT = @GNULIB_FSTATAT@ +GNULIB_FSYNC = @GNULIB_FSYNC@ +GNULIB_FTELL = @GNULIB_FTELL@ +GNULIB_FTELLO = @GNULIB_FTELLO@ +GNULIB_FTRUNCATE = @GNULIB_FTRUNCATE@ +GNULIB_FUTIMENS = @GNULIB_FUTIMENS@ +GNULIB_FWRITE = @GNULIB_FWRITE@ +GNULIB_GETCWD = @GNULIB_GETCWD@ +GNULIB_GETDELIM = @GNULIB_GETDELIM@ +GNULIB_GETDOMAINNAME = @GNULIB_GETDOMAINNAME@ +GNULIB_GETDTABLESIZE = @GNULIB_GETDTABLESIZE@ +GNULIB_GETGROUPS = @GNULIB_GETGROUPS@ +GNULIB_GETHOSTNAME = @GNULIB_GETHOSTNAME@ +GNULIB_GETLINE = @GNULIB_GETLINE@ +GNULIB_GETLOADAVG = @GNULIB_GETLOADAVG@ +GNULIB_GETLOGIN = @GNULIB_GETLOGIN@ +GNULIB_GETLOGIN_R = @GNULIB_GETLOGIN_R@ +GNULIB_GETPAGESIZE = @GNULIB_GETPAGESIZE@ +GNULIB_GETSUBOPT = @GNULIB_GETSUBOPT@ +GNULIB_GETTIMEOFDAY = @GNULIB_GETTIMEOFDAY@ +GNULIB_GETUSERSHELL = @GNULIB_GETUSERSHELL@ +GNULIB_GRANTPT = @GNULIB_GRANTPT@ +GNULIB_ISFINITE = @GNULIB_ISFINITE@ +GNULIB_ISINF = @GNULIB_ISINF@ +GNULIB_ISNAN = @GNULIB_ISNAN@ +GNULIB_ISNAND = @GNULIB_ISNAND@ +GNULIB_ISNANF = @GNULIB_ISNANF@ +GNULIB_ISNANL = @GNULIB_ISNANL@ +GNULIB_ISWBLANK = @GNULIB_ISWBLANK@ +GNULIB_ISWCTYPE = @GNULIB_ISWCTYPE@ +GNULIB_LCHMOD = @GNULIB_LCHMOD@ +GNULIB_LCHOWN = @GNULIB_LCHOWN@ +GNULIB_LDEXPL = @GNULIB_LDEXPL@ +GNULIB_LINK = @GNULIB_LINK@ +GNULIB_LINKAT = @GNULIB_LINKAT@ +GNULIB_LOGB = @GNULIB_LOGB@ +GNULIB_LOGL = @GNULIB_LOGL@ +GNULIB_LSEEK = @GNULIB_LSEEK@ +GNULIB_LSTAT = @GNULIB_LSTAT@ +GNULIB_MALLOC_POSIX = @GNULIB_MALLOC_POSIX@ +GNULIB_MBRLEN = @GNULIB_MBRLEN@ +GNULIB_MBRTOWC = @GNULIB_MBRTOWC@ +GNULIB_MBSCASECMP = @GNULIB_MBSCASECMP@ +GNULIB_MBSCASESTR = @GNULIB_MBSCASESTR@ +GNULIB_MBSCHR = @GNULIB_MBSCHR@ +GNULIB_MBSCSPN = @GNULIB_MBSCSPN@ +GNULIB_MBSINIT = @GNULIB_MBSINIT@ +GNULIB_MBSLEN = @GNULIB_MBSLEN@ +GNULIB_MBSNCASECMP = @GNULIB_MBSNCASECMP@ +GNULIB_MBSNLEN = @GNULIB_MBSNLEN@ +GNULIB_MBSNRTOWCS = @GNULIB_MBSNRTOWCS@ +GNULIB_MBSPBRK = @GNULIB_MBSPBRK@ +GNULIB_MBSPCASECMP = @GNULIB_MBSPCASECMP@ +GNULIB_MBSRCHR = @GNULIB_MBSRCHR@ +GNULIB_MBSRTOWCS = @GNULIB_MBSRTOWCS@ +GNULIB_MBSSEP = @GNULIB_MBSSEP@ +GNULIB_MBSSPN = @GNULIB_MBSSPN@ +GNULIB_MBSSTR = @GNULIB_MBSSTR@ +GNULIB_MBSTOK_R = @GNULIB_MBSTOK_R@ +GNULIB_MBTOWC = @GNULIB_MBTOWC@ +GNULIB_MEMCHR = @GNULIB_MEMCHR@ +GNULIB_MEMMEM = @GNULIB_MEMMEM@ +GNULIB_MEMPCPY = @GNULIB_MEMPCPY@ +GNULIB_MEMRCHR = @GNULIB_MEMRCHR@ +GNULIB_MKDIRAT = @GNULIB_MKDIRAT@ +GNULIB_MKDTEMP = @GNULIB_MKDTEMP@ +GNULIB_MKFIFO = @GNULIB_MKFIFO@ +GNULIB_MKFIFOAT = @GNULIB_MKFIFOAT@ +GNULIB_MKNOD = @GNULIB_MKNOD@ +GNULIB_MKNODAT = @GNULIB_MKNODAT@ +GNULIB_MKOSTEMP = @GNULIB_MKOSTEMP@ +GNULIB_MKOSTEMPS = @GNULIB_MKOSTEMPS@ +GNULIB_MKSTEMP = @GNULIB_MKSTEMP@ +GNULIB_MKSTEMPS = @GNULIB_MKSTEMPS@ +GNULIB_MKTIME = @GNULIB_MKTIME@ +GNULIB_NANOSLEEP = @GNULIB_NANOSLEEP@ +GNULIB_NL_LANGINFO = @GNULIB_NL_LANGINFO@ +GNULIB_OBSTACK_PRINTF = @GNULIB_OBSTACK_PRINTF@ +GNULIB_OBSTACK_PRINTF_POSIX = @GNULIB_OBSTACK_PRINTF_POSIX@ +GNULIB_OPEN = @GNULIB_OPEN@ +GNULIB_OPENAT = @GNULIB_OPENAT@ +GNULIB_PERROR = @GNULIB_PERROR@ +GNULIB_PIPE = @GNULIB_PIPE@ +GNULIB_PIPE2 = @GNULIB_PIPE2@ +GNULIB_POPEN = @GNULIB_POPEN@ +GNULIB_POSIX_SPAWN = @GNULIB_POSIX_SPAWN@ +GNULIB_POSIX_SPAWNATTR_DESTROY = @GNULIB_POSIX_SPAWNATTR_DESTROY@ +GNULIB_POSIX_SPAWNATTR_GETFLAGS = @GNULIB_POSIX_SPAWNATTR_GETFLAGS@ +GNULIB_POSIX_SPAWNATTR_GETPGROUP = @GNULIB_POSIX_SPAWNATTR_GETPGROUP@ +GNULIB_POSIX_SPAWNATTR_GETSCHEDPARAM = @GNULIB_POSIX_SPAWNATTR_GETSCHEDPARAM@ +GNULIB_POSIX_SPAWNATTR_GETSCHEDPOLICY = @GNULIB_POSIX_SPAWNATTR_GETSCHEDPOLICY@ +GNULIB_POSIX_SPAWNATTR_GETSIGDEFAULT = @GNULIB_POSIX_SPAWNATTR_GETSIGDEFAULT@ +GNULIB_POSIX_SPAWNATTR_GETSIGMASK = @GNULIB_POSIX_SPAWNATTR_GETSIGMASK@ +GNULIB_POSIX_SPAWNATTR_INIT = @GNULIB_POSIX_SPAWNATTR_INIT@ +GNULIB_POSIX_SPAWNATTR_SETFLAGS = @GNULIB_POSIX_SPAWNATTR_SETFLAGS@ +GNULIB_POSIX_SPAWNATTR_SETPGROUP = @GNULIB_POSIX_SPAWNATTR_SETPGROUP@ +GNULIB_POSIX_SPAWNATTR_SETSCHEDPARAM = @GNULIB_POSIX_SPAWNATTR_SETSCHEDPARAM@ +GNULIB_POSIX_SPAWNATTR_SETSCHEDPOLICY = @GNULIB_POSIX_SPAWNATTR_SETSCHEDPOLICY@ +GNULIB_POSIX_SPAWNATTR_SETSIGDEFAULT = @GNULIB_POSIX_SPAWNATTR_SETSIGDEFAULT@ +GNULIB_POSIX_SPAWNATTR_SETSIGMASK = @GNULIB_POSIX_SPAWNATTR_SETSIGMASK@ +GNULIB_POSIX_SPAWNP = @GNULIB_POSIX_SPAWNP@ +GNULIB_POSIX_SPAWN_FILE_ACTIONS_ADDCLOSE = @GNULIB_POSIX_SPAWN_FILE_ACTIONS_ADDCLOSE@ +GNULIB_POSIX_SPAWN_FILE_ACTIONS_ADDDUP2 = @GNULIB_POSIX_SPAWN_FILE_ACTIONS_ADDDUP2@ +GNULIB_POSIX_SPAWN_FILE_ACTIONS_ADDOPEN = @GNULIB_POSIX_SPAWN_FILE_ACTIONS_ADDOPEN@ +GNULIB_POSIX_SPAWN_FILE_ACTIONS_DESTROY = @GNULIB_POSIX_SPAWN_FILE_ACTIONS_DESTROY@ +GNULIB_POSIX_SPAWN_FILE_ACTIONS_INIT = @GNULIB_POSIX_SPAWN_FILE_ACTIONS_INIT@ +GNULIB_PREAD = @GNULIB_PREAD@ +GNULIB_PRINTF = @GNULIB_PRINTF@ +GNULIB_PRINTF_POSIX = @GNULIB_PRINTF_POSIX@ +GNULIB_PTSNAME = @GNULIB_PTSNAME@ +GNULIB_PUTC = @GNULIB_PUTC@ +GNULIB_PUTCHAR = @GNULIB_PUTCHAR@ +GNULIB_PUTENV = @GNULIB_PUTENV@ +GNULIB_PUTS = @GNULIB_PUTS@ +GNULIB_PWRITE = @GNULIB_PWRITE@ +GNULIB_RANDOM_R = @GNULIB_RANDOM_R@ +GNULIB_RAWMEMCHR = @GNULIB_RAWMEMCHR@ +GNULIB_READLINK = @GNULIB_READLINK@ +GNULIB_READLINKAT = @GNULIB_READLINKAT@ +GNULIB_REALLOC_POSIX = @GNULIB_REALLOC_POSIX@ +GNULIB_REALPATH = @GNULIB_REALPATH@ +GNULIB_REMOVE = @GNULIB_REMOVE@ +GNULIB_RENAME = @GNULIB_RENAME@ +GNULIB_RENAMEAT = @GNULIB_RENAMEAT@ +GNULIB_RMDIR = @GNULIB_RMDIR@ +GNULIB_ROUND = @GNULIB_ROUND@ +GNULIB_ROUNDF = @GNULIB_ROUNDF@ +GNULIB_ROUNDL = @GNULIB_ROUNDL@ +GNULIB_RPMATCH = @GNULIB_RPMATCH@ +GNULIB_SETENV = @GNULIB_SETENV@ +GNULIB_SETLOCALE = @GNULIB_SETLOCALE@ +GNULIB_SIGACTION = @GNULIB_SIGACTION@ +GNULIB_SIGNAL_H_SIGPIPE = @GNULIB_SIGNAL_H_SIGPIPE@ +GNULIB_SIGNBIT = @GNULIB_SIGNBIT@ +GNULIB_SIGPROCMASK = @GNULIB_SIGPROCMASK@ +GNULIB_SINL = @GNULIB_SINL@ +GNULIB_SLEEP = @GNULIB_SLEEP@ +GNULIB_SNPRINTF = @GNULIB_SNPRINTF@ +GNULIB_SPRINTF_POSIX = @GNULIB_SPRINTF_POSIX@ +GNULIB_SQRTL = @GNULIB_SQRTL@ +GNULIB_STAT = @GNULIB_STAT@ +GNULIB_STDIO_H_SIGPIPE = @GNULIB_STDIO_H_SIGPIPE@ +GNULIB_STPCPY = @GNULIB_STPCPY@ +GNULIB_STPNCPY = @GNULIB_STPNCPY@ +GNULIB_STRCASESTR = @GNULIB_STRCASESTR@ +GNULIB_STRCHRNUL = @GNULIB_STRCHRNUL@ +GNULIB_STRDUP = @GNULIB_STRDUP@ +GNULIB_STRERROR = @GNULIB_STRERROR@ +GNULIB_STRERROR_R = @GNULIB_STRERROR_R@ +GNULIB_STRNCAT = @GNULIB_STRNCAT@ +GNULIB_STRNDUP = @GNULIB_STRNDUP@ +GNULIB_STRNLEN = @GNULIB_STRNLEN@ +GNULIB_STRPBRK = @GNULIB_STRPBRK@ +GNULIB_STRPTIME = @GNULIB_STRPTIME@ +GNULIB_STRSEP = @GNULIB_STRSEP@ +GNULIB_STRSIGNAL = @GNULIB_STRSIGNAL@ +GNULIB_STRSTR = @GNULIB_STRSTR@ +GNULIB_STRTOD = @GNULIB_STRTOD@ +GNULIB_STRTOK_R = @GNULIB_STRTOK_R@ +GNULIB_STRTOLL = @GNULIB_STRTOLL@ +GNULIB_STRTOULL = @GNULIB_STRTOULL@ +GNULIB_STRVERSCMP = @GNULIB_STRVERSCMP@ +GNULIB_SYMLINK = @GNULIB_SYMLINK@ +GNULIB_SYMLINKAT = @GNULIB_SYMLINKAT@ +GNULIB_SYSTEM_POSIX = @GNULIB_SYSTEM_POSIX@ +GNULIB_TANL = @GNULIB_TANL@ +GNULIB_TIMEGM = @GNULIB_TIMEGM@ +GNULIB_TIME_R = @GNULIB_TIME_R@ +GNULIB_TMPFILE = @GNULIB_TMPFILE@ +GNULIB_TOWCTRANS = @GNULIB_TOWCTRANS@ +GNULIB_TRUNC = @GNULIB_TRUNC@ +GNULIB_TRUNCF = @GNULIB_TRUNCF@ +GNULIB_TRUNCL = @GNULIB_TRUNCL@ +GNULIB_TTYNAME_R = @GNULIB_TTYNAME_R@ +GNULIB_UNISTD_H_GETOPT = @GNULIB_UNISTD_H_GETOPT@ +GNULIB_UNISTD_H_SIGPIPE = @GNULIB_UNISTD_H_SIGPIPE@ +GNULIB_UNLINK = @GNULIB_UNLINK@ +GNULIB_UNLINKAT = @GNULIB_UNLINKAT@ +GNULIB_UNLOCKPT = @GNULIB_UNLOCKPT@ +GNULIB_UNSETENV = @GNULIB_UNSETENV@ +GNULIB_USLEEP = @GNULIB_USLEEP@ +GNULIB_UTIMENSAT = @GNULIB_UTIMENSAT@ +GNULIB_VASPRINTF = @GNULIB_VASPRINTF@ +GNULIB_VDPRINTF = @GNULIB_VDPRINTF@ +GNULIB_VFPRINTF = @GNULIB_VFPRINTF@ +GNULIB_VFPRINTF_POSIX = @GNULIB_VFPRINTF_POSIX@ +GNULIB_VPRINTF = @GNULIB_VPRINTF@ +GNULIB_VPRINTF_POSIX = @GNULIB_VPRINTF_POSIX@ +GNULIB_VSNPRINTF = @GNULIB_VSNPRINTF@ +GNULIB_VSPRINTF_POSIX = @GNULIB_VSPRINTF_POSIX@ +GNULIB_WAITPID = @GNULIB_WAITPID@ +GNULIB_WCPCPY = @GNULIB_WCPCPY@ +GNULIB_WCPNCPY = @GNULIB_WCPNCPY@ +GNULIB_WCRTOMB = @GNULIB_WCRTOMB@ +GNULIB_WCSCASECMP = @GNULIB_WCSCASECMP@ +GNULIB_WCSCAT = @GNULIB_WCSCAT@ +GNULIB_WCSCHR = @GNULIB_WCSCHR@ +GNULIB_WCSCMP = @GNULIB_WCSCMP@ +GNULIB_WCSCOLL = @GNULIB_WCSCOLL@ +GNULIB_WCSCPY = @GNULIB_WCSCPY@ +GNULIB_WCSCSPN = @GNULIB_WCSCSPN@ +GNULIB_WCSDUP = @GNULIB_WCSDUP@ +GNULIB_WCSLEN = @GNULIB_WCSLEN@ +GNULIB_WCSNCASECMP = @GNULIB_WCSNCASECMP@ +GNULIB_WCSNCAT = @GNULIB_WCSNCAT@ +GNULIB_WCSNCMP = @GNULIB_WCSNCMP@ +GNULIB_WCSNCPY = @GNULIB_WCSNCPY@ +GNULIB_WCSNLEN = @GNULIB_WCSNLEN@ +GNULIB_WCSNRTOMBS = @GNULIB_WCSNRTOMBS@ +GNULIB_WCSPBRK = @GNULIB_WCSPBRK@ +GNULIB_WCSRCHR = @GNULIB_WCSRCHR@ +GNULIB_WCSRTOMBS = @GNULIB_WCSRTOMBS@ +GNULIB_WCSSPN = @GNULIB_WCSSPN@ +GNULIB_WCSSTR = @GNULIB_WCSSTR@ +GNULIB_WCSTOK = @GNULIB_WCSTOK@ +GNULIB_WCSWIDTH = @GNULIB_WCSWIDTH@ +GNULIB_WCSXFRM = @GNULIB_WCSXFRM@ +GNULIB_WCTOB = @GNULIB_WCTOB@ +GNULIB_WCTOMB = @GNULIB_WCTOMB@ +GNULIB_WCTRANS = @GNULIB_WCTRANS@ +GNULIB_WCTYPE = @GNULIB_WCTYPE@ +GNULIB_WCWIDTH = @GNULIB_WCWIDTH@ +GNULIB_WMEMCHR = @GNULIB_WMEMCHR@ +GNULIB_WMEMCMP = @GNULIB_WMEMCMP@ +GNULIB_WMEMCPY = @GNULIB_WMEMCPY@ +GNULIB_WMEMMOVE = @GNULIB_WMEMMOVE@ +GNULIB_WMEMSET = @GNULIB_WMEMSET@ +GNULIB_WRITE = @GNULIB_WRITE@ +GNULIB__EXIT = @GNULIB__EXIT@ +GREP = @GREP@ +HAVE_ACOSL = @HAVE_ACOSL@ +HAVE_ASINL = @HAVE_ASINL@ +HAVE_ATANL = @HAVE_ATANL@ +HAVE_ATOLL = @HAVE_ATOLL@ +HAVE_BTOWC = @HAVE_BTOWC@ +HAVE_CANONICALIZE_FILE_NAME = @HAVE_CANONICALIZE_FILE_NAME@ +HAVE_CHOWN = @HAVE_CHOWN@ +HAVE_COSL = @HAVE_COSL@ +HAVE_DECL_ACOSL = @HAVE_DECL_ACOSL@ +HAVE_DECL_ASINL = @HAVE_DECL_ASINL@ +HAVE_DECL_ATANL = @HAVE_DECL_ATANL@ +HAVE_DECL_CEILF = @HAVE_DECL_CEILF@ +HAVE_DECL_CEILL = @HAVE_DECL_CEILL@ +HAVE_DECL_COSL = @HAVE_DECL_COSL@ +HAVE_DECL_ENVIRON = @HAVE_DECL_ENVIRON@ +HAVE_DECL_EXPL = @HAVE_DECL_EXPL@ +HAVE_DECL_FCHDIR = @HAVE_DECL_FCHDIR@ +HAVE_DECL_FLOORF = @HAVE_DECL_FLOORF@ +HAVE_DECL_FLOORL = @HAVE_DECL_FLOORL@ +HAVE_DECL_FPURGE = @HAVE_DECL_FPURGE@ +HAVE_DECL_FREXPL = @HAVE_DECL_FREXPL@ +HAVE_DECL_FSEEKO = @HAVE_DECL_FSEEKO@ +HAVE_DECL_FTELLO = @HAVE_DECL_FTELLO@ +HAVE_DECL_GETDELIM = @HAVE_DECL_GETDELIM@ +HAVE_DECL_GETDOMAINNAME = @HAVE_DECL_GETDOMAINNAME@ +HAVE_DECL_GETLINE = @HAVE_DECL_GETLINE@ +HAVE_DECL_GETLOADAVG = @HAVE_DECL_GETLOADAVG@ +HAVE_DECL_GETLOGIN_R = @HAVE_DECL_GETLOGIN_R@ +HAVE_DECL_GETPAGESIZE = @HAVE_DECL_GETPAGESIZE@ +HAVE_DECL_GETUSERSHELL = @HAVE_DECL_GETUSERSHELL@ +HAVE_DECL_LDEXPL = @HAVE_DECL_LDEXPL@ +HAVE_DECL_LOCALTIME_R = @HAVE_DECL_LOCALTIME_R@ +HAVE_DECL_LOGB = @HAVE_DECL_LOGB@ +HAVE_DECL_LOGL = @HAVE_DECL_LOGL@ +HAVE_DECL_MEMMEM = @HAVE_DECL_MEMMEM@ +HAVE_DECL_MEMRCHR = @HAVE_DECL_MEMRCHR@ +HAVE_DECL_OBSTACK_PRINTF = @HAVE_DECL_OBSTACK_PRINTF@ +HAVE_DECL_ROUND = @HAVE_DECL_ROUND@ +HAVE_DECL_ROUNDF = @HAVE_DECL_ROUNDF@ +HAVE_DECL_ROUNDL = @HAVE_DECL_ROUNDL@ +HAVE_DECL_SETENV = @HAVE_DECL_SETENV@ +HAVE_DECL_SINL = @HAVE_DECL_SINL@ +HAVE_DECL_SNPRINTF = @HAVE_DECL_SNPRINTF@ +HAVE_DECL_SQRTL = @HAVE_DECL_SQRTL@ +HAVE_DECL_STRDUP = @HAVE_DECL_STRDUP@ +HAVE_DECL_STRERROR_R = @HAVE_DECL_STRERROR_R@ +HAVE_DECL_STRNDUP = @HAVE_DECL_STRNDUP@ +HAVE_DECL_STRNLEN = @HAVE_DECL_STRNLEN@ +HAVE_DECL_STRSIGNAL = @HAVE_DECL_STRSIGNAL@ +HAVE_DECL_STRTOK_R = @HAVE_DECL_STRTOK_R@ +HAVE_DECL_TANL = @HAVE_DECL_TANL@ +HAVE_DECL_TRUNC = @HAVE_DECL_TRUNC@ +HAVE_DECL_TRUNCF = @HAVE_DECL_TRUNCF@ +HAVE_DECL_TRUNCL = @HAVE_DECL_TRUNCL@ +HAVE_DECL_TTYNAME_R = @HAVE_DECL_TTYNAME_R@ +HAVE_DECL_UNSETENV = @HAVE_DECL_UNSETENV@ +HAVE_DECL_VSNPRINTF = @HAVE_DECL_VSNPRINTF@ +HAVE_DECL_WCTOB = @HAVE_DECL_WCTOB@ +HAVE_DECL_WCWIDTH = @HAVE_DECL_WCWIDTH@ +HAVE_DPRINTF = @HAVE_DPRINTF@ +HAVE_DUP2 = @HAVE_DUP2@ +HAVE_DUP3 = @HAVE_DUP3@ +HAVE_DUPLOCALE = @HAVE_DUPLOCALE@ +HAVE_EUIDACCESS = @HAVE_EUIDACCESS@ +HAVE_EXPL = @HAVE_EXPL@ +HAVE_FACCESSAT = @HAVE_FACCESSAT@ +HAVE_FCHDIR = @HAVE_FCHDIR@ +HAVE_FCHMODAT = @HAVE_FCHMODAT@ +HAVE_FCHOWNAT = @HAVE_FCHOWNAT@ +HAVE_FCNTL = @HAVE_FCNTL@ +HAVE_FEATURES_H = @HAVE_FEATURES_H@ +HAVE_FSEEKO = @HAVE_FSEEKO@ +HAVE_FSTATAT = @HAVE_FSTATAT@ +HAVE_FSYNC = @HAVE_FSYNC@ +HAVE_FTELLO = @HAVE_FTELLO@ +HAVE_FTRUNCATE = @HAVE_FTRUNCATE@ +HAVE_FUTIMENS = @HAVE_FUTIMENS@ +HAVE_GETDTABLESIZE = @HAVE_GETDTABLESIZE@ +HAVE_GETGROUPS = @HAVE_GETGROUPS@ +HAVE_GETHOSTNAME = @HAVE_GETHOSTNAME@ +HAVE_GETLOGIN = @HAVE_GETLOGIN@ +HAVE_GETOPT_H = @HAVE_GETOPT_H@ +HAVE_GETPAGESIZE = @HAVE_GETPAGESIZE@ +HAVE_GETSUBOPT = @HAVE_GETSUBOPT@ +HAVE_GETTIMEOFDAY = @HAVE_GETTIMEOFDAY@ +HAVE_GRANTPT = @HAVE_GRANTPT@ +HAVE_INTTYPES_H = @HAVE_INTTYPES_H@ +HAVE_ISNAND = @HAVE_ISNAND@ +HAVE_ISNANF = @HAVE_ISNANF@ +HAVE_ISNANL = @HAVE_ISNANL@ +HAVE_ISWBLANK = @HAVE_ISWBLANK@ +HAVE_ISWCNTRL = @HAVE_ISWCNTRL@ +HAVE_LANGINFO_CODESET = @HAVE_LANGINFO_CODESET@ +HAVE_LANGINFO_ERA = @HAVE_LANGINFO_ERA@ +HAVE_LANGINFO_H = @HAVE_LANGINFO_H@ +HAVE_LANGINFO_T_FMT_AMPM = @HAVE_LANGINFO_T_FMT_AMPM@ +HAVE_LANGINFO_YESEXPR = @HAVE_LANGINFO_YESEXPR@ +HAVE_LCHMOD = @HAVE_LCHMOD@ +HAVE_LCHOWN = @HAVE_LCHOWN@ +HAVE_LIBSIGSEGV = @HAVE_LIBSIGSEGV@ +HAVE_LINK = @HAVE_LINK@ +HAVE_LINKAT = @HAVE_LINKAT@ +HAVE_LOGL = @HAVE_LOGL@ +HAVE_LONG_LONG_INT = @HAVE_LONG_LONG_INT@ +HAVE_LSTAT = @HAVE_LSTAT@ +HAVE_MBRLEN = @HAVE_MBRLEN@ +HAVE_MBRTOWC = @HAVE_MBRTOWC@ +HAVE_MBSINIT = @HAVE_MBSINIT@ +HAVE_MBSLEN = @HAVE_MBSLEN@ +HAVE_MBSNRTOWCS = @HAVE_MBSNRTOWCS@ +HAVE_MBSRTOWCS = @HAVE_MBSRTOWCS@ +HAVE_MEMCHR = @HAVE_MEMCHR@ +HAVE_MEMPCPY = @HAVE_MEMPCPY@ +HAVE_MKDIRAT = @HAVE_MKDIRAT@ +HAVE_MKDTEMP = @HAVE_MKDTEMP@ +HAVE_MKFIFO = @HAVE_MKFIFO@ +HAVE_MKFIFOAT = @HAVE_MKFIFOAT@ +HAVE_MKNOD = @HAVE_MKNOD@ +HAVE_MKNODAT = @HAVE_MKNODAT@ +HAVE_MKOSTEMP = @HAVE_MKOSTEMP@ +HAVE_MKOSTEMPS = @HAVE_MKOSTEMPS@ +HAVE_MKSTEMP = @HAVE_MKSTEMP@ +HAVE_MKSTEMPS = @HAVE_MKSTEMPS@ +HAVE_NANOSLEEP = @HAVE_NANOSLEEP@ +HAVE_NL_LANGINFO = @HAVE_NL_LANGINFO@ +HAVE_OPENAT = @HAVE_OPENAT@ +HAVE_OS_H = @HAVE_OS_H@ +HAVE_PIPE = @HAVE_PIPE@ +HAVE_PIPE2 = @HAVE_PIPE2@ +HAVE_POSIX_SIGNALBLOCKING = @HAVE_POSIX_SIGNALBLOCKING@ +HAVE_POSIX_SPAWN = @HAVE_POSIX_SPAWN@ +HAVE_POSIX_SPAWNATTR_T = @HAVE_POSIX_SPAWNATTR_T@ +HAVE_POSIX_SPAWN_FILE_ACTIONS_T = @HAVE_POSIX_SPAWN_FILE_ACTIONS_T@ +HAVE_PREAD = @HAVE_PREAD@ +HAVE_PTSNAME = @HAVE_PTSNAME@ +HAVE_PWRITE = @HAVE_PWRITE@ +HAVE_RANDOM_H = @HAVE_RANDOM_H@ +HAVE_RANDOM_R = @HAVE_RANDOM_R@ +HAVE_RAWMEMCHR = @HAVE_RAWMEMCHR@ +HAVE_READLINK = @HAVE_READLINK@ +HAVE_READLINKAT = @HAVE_READLINKAT@ +HAVE_REALPATH = @HAVE_REALPATH@ +HAVE_RENAMEAT = @HAVE_RENAMEAT@ +HAVE_RPMATCH = @HAVE_RPMATCH@ +HAVE_SCHED_H = @HAVE_SCHED_H@ +HAVE_SETENV = @HAVE_SETENV@ +HAVE_SIGACTION = @HAVE_SIGACTION@ +HAVE_SIGINFO_T = @HAVE_SIGINFO_T@ +HAVE_SIGNED_SIG_ATOMIC_T = @HAVE_SIGNED_SIG_ATOMIC_T@ +HAVE_SIGNED_WCHAR_T = @HAVE_SIGNED_WCHAR_T@ +HAVE_SIGNED_WINT_T = @HAVE_SIGNED_WINT_T@ +HAVE_SIGSET_T = @HAVE_SIGSET_T@ +HAVE_SINL = @HAVE_SINL@ +HAVE_SLEEP = @HAVE_SLEEP@ +HAVE_SPAWN_H = @HAVE_SPAWN_H@ +HAVE_SQRTL = @HAVE_SQRTL@ +HAVE_STDINT_H = @HAVE_STDINT_H@ +HAVE_STPCPY = @HAVE_STPCPY@ +HAVE_STPNCPY = @HAVE_STPNCPY@ +HAVE_STRCASESTR = @HAVE_STRCASESTR@ +HAVE_STRCHRNUL = @HAVE_STRCHRNUL@ +HAVE_STRPBRK = @HAVE_STRPBRK@ +HAVE_STRPTIME = @HAVE_STRPTIME@ +HAVE_STRSEP = @HAVE_STRSEP@ +HAVE_STRTOD = @HAVE_STRTOD@ +HAVE_STRTOLL = @HAVE_STRTOLL@ +HAVE_STRTOULL = @HAVE_STRTOULL@ +HAVE_STRUCT_RANDOM_DATA = @HAVE_STRUCT_RANDOM_DATA@ +HAVE_STRUCT_SCHED_PARAM = @HAVE_STRUCT_SCHED_PARAM@ +HAVE_STRUCT_SIGACTION_SA_SIGACTION = @HAVE_STRUCT_SIGACTION_SA_SIGACTION@ +HAVE_STRUCT_TIMEVAL = @HAVE_STRUCT_TIMEVAL@ +HAVE_STRVERSCMP = @HAVE_STRVERSCMP@ +HAVE_SYMLINK = @HAVE_SYMLINK@ +HAVE_SYMLINKAT = @HAVE_SYMLINKAT@ +HAVE_SYS_BITYPES_H = @HAVE_SYS_BITYPES_H@ +HAVE_SYS_INTTYPES_H = @HAVE_SYS_INTTYPES_H@ +HAVE_SYS_LOADAVG_H = @HAVE_SYS_LOADAVG_H@ +HAVE_SYS_PARAM_H = @HAVE_SYS_PARAM_H@ +HAVE_SYS_TIME_H = @HAVE_SYS_TIME_H@ +HAVE_SYS_TYPES_H = @HAVE_SYS_TYPES_H@ +HAVE_TANL = @HAVE_TANL@ +HAVE_TIMEGM = @HAVE_TIMEGM@ +HAVE_TYPE_VOLATILE_SIG_ATOMIC_T = @HAVE_TYPE_VOLATILE_SIG_ATOMIC_T@ +HAVE_UNISTD_H = @HAVE_UNISTD_H@ +HAVE_UNLINKAT = @HAVE_UNLINKAT@ +HAVE_UNLOCKPT = @HAVE_UNLOCKPT@ +HAVE_UNSIGNED_LONG_LONG_INT = @HAVE_UNSIGNED_LONG_LONG_INT@ +HAVE_USLEEP = @HAVE_USLEEP@ +HAVE_UTIMENSAT = @HAVE_UTIMENSAT@ +HAVE_VASPRINTF = @HAVE_VASPRINTF@ +HAVE_VDPRINTF = @HAVE_VDPRINTF@ +HAVE_WCHAR_H = @HAVE_WCHAR_H@ +HAVE_WCHAR_T = @HAVE_WCHAR_T@ +HAVE_WCPCPY = @HAVE_WCPCPY@ +HAVE_WCPNCPY = @HAVE_WCPNCPY@ +HAVE_WCRTOMB = @HAVE_WCRTOMB@ +HAVE_WCSCASECMP = @HAVE_WCSCASECMP@ +HAVE_WCSCAT = @HAVE_WCSCAT@ +HAVE_WCSCHR = @HAVE_WCSCHR@ +HAVE_WCSCMP = @HAVE_WCSCMP@ +HAVE_WCSCOLL = @HAVE_WCSCOLL@ +HAVE_WCSCPY = @HAVE_WCSCPY@ +HAVE_WCSCSPN = @HAVE_WCSCSPN@ +HAVE_WCSDUP = @HAVE_WCSDUP@ +HAVE_WCSLEN = @HAVE_WCSLEN@ +HAVE_WCSNCASECMP = @HAVE_WCSNCASECMP@ +HAVE_WCSNCAT = @HAVE_WCSNCAT@ +HAVE_WCSNCMP = @HAVE_WCSNCMP@ +HAVE_WCSNCPY = @HAVE_WCSNCPY@ +HAVE_WCSNLEN = @HAVE_WCSNLEN@ +HAVE_WCSNRTOMBS = @HAVE_WCSNRTOMBS@ +HAVE_WCSPBRK = @HAVE_WCSPBRK@ +HAVE_WCSRCHR = @HAVE_WCSRCHR@ +HAVE_WCSRTOMBS = @HAVE_WCSRTOMBS@ +HAVE_WCSSPN = @HAVE_WCSSPN@ +HAVE_WCSSTR = @HAVE_WCSSTR@ +HAVE_WCSTOK = @HAVE_WCSTOK@ +HAVE_WCSWIDTH = @HAVE_WCSWIDTH@ +HAVE_WCSXFRM = @HAVE_WCSXFRM@ +HAVE_WCTRANS_T = @HAVE_WCTRANS_T@ +HAVE_WCTYPE_H = @HAVE_WCTYPE_H@ +HAVE_WCTYPE_T = @HAVE_WCTYPE_T@ +HAVE_WINT_T = @HAVE_WINT_T@ +HAVE_WMEMCHR = @HAVE_WMEMCHR@ +HAVE_WMEMCMP = @HAVE_WMEMCMP@ +HAVE_WMEMCPY = @HAVE_WMEMCPY@ +HAVE_WMEMMOVE = @HAVE_WMEMMOVE@ +HAVE_WMEMSET = @HAVE_WMEMSET@ +HAVE_XLOCALE_H = @HAVE_XLOCALE_H@ +HAVE__BOOL = @HAVE__BOOL@ +HAVE__EXIT = @HAVE__EXIT@ +INCLUDE_NEXT = @INCLUDE_NEXT@ +INCLUDE_NEXT_AS_FIRST_DIRECTIVE = @INCLUDE_NEXT_AS_FIRST_DIRECTIVE@ +INSTALL = @INSTALL@ +INSTALL_DATA = @INSTALL_DATA@ +INSTALL_PROGRAM = @INSTALL_PROGRAM@ +INSTALL_SCRIPT = @INSTALL_SCRIPT@ +INSTALL_STRIP_PROGRAM = @INSTALL_STRIP_PROGRAM@ +INTL_MACOSX_LIBS = @INTL_MACOSX_LIBS@ +LDFLAGS = @LDFLAGS@ +LIBCSTACK = @LIBCSTACK@ +LIBINTL = @LIBINTL@ +LIBM4_LIBDEPS = @LIBM4_LIBDEPS@ +LIBM4_LTLIBDEPS = @LIBM4_LTLIBDEPS@ +LIBMULTITHREAD = @LIBMULTITHREAD@ +LIBOBJS = @LIBOBJS@ +LIBPTH = @LIBPTH@ +LIBPTH_PREFIX = @LIBPTH_PREFIX@ +LIBS = @LIBS@ +LIBSIGSEGV = @LIBSIGSEGV@ +LIBSIGSEGV_PREFIX = @LIBSIGSEGV_PREFIX@ +LIBTESTS_LIBDEPS = @LIBTESTS_LIBDEPS@ +LIBTHREAD = @LIBTHREAD@ +LOCALCHARSET_TESTS_ENVIRONMENT = @LOCALCHARSET_TESTS_ENVIRONMENT@ +LOCALE_FR = @LOCALE_FR@ +LOCALE_FR_UTF8 = @LOCALE_FR_UTF8@ +LOCALE_JA = @LOCALE_JA@ +LOCALE_TR_UTF8 = @LOCALE_TR_UTF8@ +LOCALE_ZH_CN = @LOCALE_ZH_CN@ +LTLIBCSTACK = @LTLIBCSTACK@ +LTLIBINTL = @LTLIBINTL@ +LTLIBMULTITHREAD = @LTLIBMULTITHREAD@ +LTLIBOBJS = @LTLIBOBJS@ +LTLIBPTH = @LTLIBPTH@ +LTLIBSIGSEGV = @LTLIBSIGSEGV@ +LTLIBTHREAD = @LTLIBTHREAD@ +M4_LIBOBJS = @M4_LIBOBJS@ +M4_LTLIBOBJS = @M4_LTLIBOBJS@ +M4tests_LIBOBJS = @M4tests_LIBOBJS@ +M4tests_LTLIBOBJS = @M4tests_LTLIBOBJS@ +M4tests_WITNESS = @M4tests_WITNESS@ +MAKEINFO = @MAKEINFO@ +MKDIR_P = @MKDIR_P@ +NEXT_AS_FIRST_DIRECTIVE_ERRNO_H = @NEXT_AS_FIRST_DIRECTIVE_ERRNO_H@ +NEXT_AS_FIRST_DIRECTIVE_FCNTL_H = @NEXT_AS_FIRST_DIRECTIVE_FCNTL_H@ +NEXT_AS_FIRST_DIRECTIVE_FLOAT_H = @NEXT_AS_FIRST_DIRECTIVE_FLOAT_H@ +NEXT_AS_FIRST_DIRECTIVE_GETOPT_H = @NEXT_AS_FIRST_DIRECTIVE_GETOPT_H@ +NEXT_AS_FIRST_DIRECTIVE_LANGINFO_H = @NEXT_AS_FIRST_DIRECTIVE_LANGINFO_H@ +NEXT_AS_FIRST_DIRECTIVE_LOCALE_H = @NEXT_AS_FIRST_DIRECTIVE_LOCALE_H@ +NEXT_AS_FIRST_DIRECTIVE_MATH_H = @NEXT_AS_FIRST_DIRECTIVE_MATH_H@ +NEXT_AS_FIRST_DIRECTIVE_SCHED_H = @NEXT_AS_FIRST_DIRECTIVE_SCHED_H@ +NEXT_AS_FIRST_DIRECTIVE_SIGNAL_H = @NEXT_AS_FIRST_DIRECTIVE_SIGNAL_H@ +NEXT_AS_FIRST_DIRECTIVE_SPAWN_H = @NEXT_AS_FIRST_DIRECTIVE_SPAWN_H@ +NEXT_AS_FIRST_DIRECTIVE_STDARG_H = @NEXT_AS_FIRST_DIRECTIVE_STDARG_H@ +NEXT_AS_FIRST_DIRECTIVE_STDDEF_H = @NEXT_AS_FIRST_DIRECTIVE_STDDEF_H@ +NEXT_AS_FIRST_DIRECTIVE_STDINT_H = @NEXT_AS_FIRST_DIRECTIVE_STDINT_H@ +NEXT_AS_FIRST_DIRECTIVE_STDIO_H = @NEXT_AS_FIRST_DIRECTIVE_STDIO_H@ +NEXT_AS_FIRST_DIRECTIVE_STDLIB_H = @NEXT_AS_FIRST_DIRECTIVE_STDLIB_H@ +NEXT_AS_FIRST_DIRECTIVE_STRING_H = @NEXT_AS_FIRST_DIRECTIVE_STRING_H@ +NEXT_AS_FIRST_DIRECTIVE_SYS_STAT_H = @NEXT_AS_FIRST_DIRECTIVE_SYS_STAT_H@ +NEXT_AS_FIRST_DIRECTIVE_SYS_TIME_H = @NEXT_AS_FIRST_DIRECTIVE_SYS_TIME_H@ +NEXT_AS_FIRST_DIRECTIVE_SYS_WAIT_H = @NEXT_AS_FIRST_DIRECTIVE_SYS_WAIT_H@ +NEXT_AS_FIRST_DIRECTIVE_TIME_H = @NEXT_AS_FIRST_DIRECTIVE_TIME_H@ +NEXT_AS_FIRST_DIRECTIVE_UNISTD_H = @NEXT_AS_FIRST_DIRECTIVE_UNISTD_H@ +NEXT_AS_FIRST_DIRECTIVE_WCHAR_H = @NEXT_AS_FIRST_DIRECTIVE_WCHAR_H@ +NEXT_AS_FIRST_DIRECTIVE_WCTYPE_H = @NEXT_AS_FIRST_DIRECTIVE_WCTYPE_H@ +NEXT_ERRNO_H = @NEXT_ERRNO_H@ +NEXT_FCNTL_H = @NEXT_FCNTL_H@ +NEXT_FLOAT_H = @NEXT_FLOAT_H@ +NEXT_GETOPT_H = @NEXT_GETOPT_H@ +NEXT_LANGINFO_H = @NEXT_LANGINFO_H@ +NEXT_LOCALE_H = @NEXT_LOCALE_H@ +NEXT_MATH_H = @NEXT_MATH_H@ +NEXT_SCHED_H = @NEXT_SCHED_H@ +NEXT_SIGNAL_H = @NEXT_SIGNAL_H@ +NEXT_SPAWN_H = @NEXT_SPAWN_H@ +NEXT_STDARG_H = @NEXT_STDARG_H@ +NEXT_STDDEF_H = @NEXT_STDDEF_H@ +NEXT_STDINT_H = @NEXT_STDINT_H@ +NEXT_STDIO_H = @NEXT_STDIO_H@ +NEXT_STDLIB_H = @NEXT_STDLIB_H@ +NEXT_STRING_H = @NEXT_STRING_H@ +NEXT_SYS_STAT_H = @NEXT_SYS_STAT_H@ +NEXT_SYS_TIME_H = @NEXT_SYS_TIME_H@ +NEXT_SYS_WAIT_H = @NEXT_SYS_WAIT_H@ +NEXT_TIME_H = @NEXT_TIME_H@ +NEXT_UNISTD_H = @NEXT_UNISTD_H@ +NEXT_WCHAR_H = @NEXT_WCHAR_H@ +NEXT_WCTYPE_H = @NEXT_WCTYPE_H@ +OBJEXT = @OBJEXT@ +PACKAGE = @PACKAGE@ +PACKAGE_BUGREPORT = @PACKAGE_BUGREPORT@ +PACKAGE_NAME = @PACKAGE_NAME@ +PACKAGE_STRING = @PACKAGE_STRING@ +PACKAGE_TARNAME = @PACKAGE_TARNAME@ +PACKAGE_URL = @PACKAGE_URL@ +PACKAGE_VERSION = @PACKAGE_VERSION@ +PATH_SEPARATOR = @PATH_SEPARATOR@ +PRAGMA_COLUMNS = @PRAGMA_COLUMNS@ +PRAGMA_SYSTEM_HEADER = @PRAGMA_SYSTEM_HEADER@ +PTHREAD_H_DEFINES_STRUCT_TIMESPEC = @PTHREAD_H_DEFINES_STRUCT_TIMESPEC@ +PTRDIFF_T_SUFFIX = @PTRDIFF_T_SUFFIX@ +RANLIB = @RANLIB@ +REPLACE_BTOWC = @REPLACE_BTOWC@ +REPLACE_CALLOC = @REPLACE_CALLOC@ +REPLACE_CANONICALIZE_FILE_NAME = @REPLACE_CANONICALIZE_FILE_NAME@ +REPLACE_CEIL = @REPLACE_CEIL@ +REPLACE_CEILF = @REPLACE_CEILF@ +REPLACE_CEILL = @REPLACE_CEILL@ +REPLACE_CHOWN = @REPLACE_CHOWN@ +REPLACE_CLOSE = @REPLACE_CLOSE@ +REPLACE_DPRINTF = @REPLACE_DPRINTF@ +REPLACE_DUP = @REPLACE_DUP@ +REPLACE_DUP2 = @REPLACE_DUP2@ +REPLACE_DUPLOCALE = @REPLACE_DUPLOCALE@ +REPLACE_FCHOWNAT = @REPLACE_FCHOWNAT@ +REPLACE_FCLOSE = @REPLACE_FCLOSE@ +REPLACE_FCNTL = @REPLACE_FCNTL@ +REPLACE_FFLUSH = @REPLACE_FFLUSH@ +REPLACE_FLOOR = @REPLACE_FLOOR@ +REPLACE_FLOORF = @REPLACE_FLOORF@ +REPLACE_FLOORL = @REPLACE_FLOORL@ +REPLACE_FOPEN = @REPLACE_FOPEN@ +REPLACE_FPRINTF = @REPLACE_FPRINTF@ +REPLACE_FPURGE = @REPLACE_FPURGE@ +REPLACE_FREOPEN = @REPLACE_FREOPEN@ +REPLACE_FREXP = @REPLACE_FREXP@ +REPLACE_FREXPL = @REPLACE_FREXPL@ +REPLACE_FSEEK = @REPLACE_FSEEK@ +REPLACE_FSEEKO = @REPLACE_FSEEKO@ +REPLACE_FSTAT = @REPLACE_FSTAT@ +REPLACE_FSTATAT = @REPLACE_FSTATAT@ +REPLACE_FTELL = @REPLACE_FTELL@ +REPLACE_FTELLO = @REPLACE_FTELLO@ +REPLACE_FUTIMENS = @REPLACE_FUTIMENS@ +REPLACE_GETCWD = @REPLACE_GETCWD@ +REPLACE_GETDELIM = @REPLACE_GETDELIM@ +REPLACE_GETDOMAINNAME = @REPLACE_GETDOMAINNAME@ +REPLACE_GETGROUPS = @REPLACE_GETGROUPS@ +REPLACE_GETLINE = @REPLACE_GETLINE@ +REPLACE_GETLOGIN_R = @REPLACE_GETLOGIN_R@ +REPLACE_GETPAGESIZE = @REPLACE_GETPAGESIZE@ +REPLACE_GETTIMEOFDAY = @REPLACE_GETTIMEOFDAY@ +REPLACE_HUGE_VAL = @REPLACE_HUGE_VAL@ +REPLACE_ISFINITE = @REPLACE_ISFINITE@ +REPLACE_ISINF = @REPLACE_ISINF@ +REPLACE_ISNAN = @REPLACE_ISNAN@ +REPLACE_ISWBLANK = @REPLACE_ISWBLANK@ +REPLACE_ISWCNTRL = @REPLACE_ISWCNTRL@ +REPLACE_LCHOWN = @REPLACE_LCHOWN@ +REPLACE_LDEXPL = @REPLACE_LDEXPL@ +REPLACE_LINK = @REPLACE_LINK@ +REPLACE_LINKAT = @REPLACE_LINKAT@ +REPLACE_LOCALTIME_R = @REPLACE_LOCALTIME_R@ +REPLACE_LSEEK = @REPLACE_LSEEK@ +REPLACE_LSTAT = @REPLACE_LSTAT@ +REPLACE_MALLOC = @REPLACE_MALLOC@ +REPLACE_MBRLEN = @REPLACE_MBRLEN@ +REPLACE_MBRTOWC = @REPLACE_MBRTOWC@ +REPLACE_MBSINIT = @REPLACE_MBSINIT@ +REPLACE_MBSNRTOWCS = @REPLACE_MBSNRTOWCS@ +REPLACE_MBSRTOWCS = @REPLACE_MBSRTOWCS@ +REPLACE_MBSTATE_T = @REPLACE_MBSTATE_T@ +REPLACE_MBTOWC = @REPLACE_MBTOWC@ +REPLACE_MEMCHR = @REPLACE_MEMCHR@ +REPLACE_MEMMEM = @REPLACE_MEMMEM@ +REPLACE_MKDIR = @REPLACE_MKDIR@ +REPLACE_MKFIFO = @REPLACE_MKFIFO@ +REPLACE_MKNOD = @REPLACE_MKNOD@ +REPLACE_MKSTEMP = @REPLACE_MKSTEMP@ +REPLACE_MKTIME = @REPLACE_MKTIME@ +REPLACE_NAN = @REPLACE_NAN@ +REPLACE_NANOSLEEP = @REPLACE_NANOSLEEP@ +REPLACE_NL_LANGINFO = @REPLACE_NL_LANGINFO@ +REPLACE_NULL = @REPLACE_NULL@ +REPLACE_OBSTACK_PRINTF = @REPLACE_OBSTACK_PRINTF@ +REPLACE_OPEN = @REPLACE_OPEN@ +REPLACE_OPENAT = @REPLACE_OPENAT@ +REPLACE_PERROR = @REPLACE_PERROR@ +REPLACE_POPEN = @REPLACE_POPEN@ +REPLACE_POSIX_SPAWN = @REPLACE_POSIX_SPAWN@ +REPLACE_PREAD = @REPLACE_PREAD@ +REPLACE_PRINTF = @REPLACE_PRINTF@ +REPLACE_PUTENV = @REPLACE_PUTENV@ +REPLACE_PWRITE = @REPLACE_PWRITE@ +REPLACE_READLINK = @REPLACE_READLINK@ +REPLACE_REALLOC = @REPLACE_REALLOC@ +REPLACE_REALPATH = @REPLACE_REALPATH@ +REPLACE_REMOVE = @REPLACE_REMOVE@ +REPLACE_RENAME = @REPLACE_RENAME@ +REPLACE_RENAMEAT = @REPLACE_RENAMEAT@ +REPLACE_RMDIR = @REPLACE_RMDIR@ +REPLACE_ROUND = @REPLACE_ROUND@ +REPLACE_ROUNDF = @REPLACE_ROUNDF@ +REPLACE_ROUNDL = @REPLACE_ROUNDL@ +REPLACE_SETENV = @REPLACE_SETENV@ +REPLACE_SETLOCALE = @REPLACE_SETLOCALE@ +REPLACE_SIGNBIT = @REPLACE_SIGNBIT@ +REPLACE_SIGNBIT_USING_GCC = @REPLACE_SIGNBIT_USING_GCC@ +REPLACE_SLEEP = @REPLACE_SLEEP@ +REPLACE_SNPRINTF = @REPLACE_SNPRINTF@ +REPLACE_SPRINTF = @REPLACE_SPRINTF@ +REPLACE_STAT = @REPLACE_STAT@ +REPLACE_STDIO_WRITE_FUNCS = @REPLACE_STDIO_WRITE_FUNCS@ +REPLACE_STPNCPY = @REPLACE_STPNCPY@ +REPLACE_STRCASESTR = @REPLACE_STRCASESTR@ +REPLACE_STRDUP = @REPLACE_STRDUP@ +REPLACE_STRERROR = @REPLACE_STRERROR@ +REPLACE_STRERROR_R = @REPLACE_STRERROR_R@ +REPLACE_STRNCAT = @REPLACE_STRNCAT@ +REPLACE_STRNDUP = @REPLACE_STRNDUP@ +REPLACE_STRNLEN = @REPLACE_STRNLEN@ +REPLACE_STRSIGNAL = @REPLACE_STRSIGNAL@ +REPLACE_STRSTR = @REPLACE_STRSTR@ +REPLACE_STRTOD = @REPLACE_STRTOD@ +REPLACE_STRTOK_R = @REPLACE_STRTOK_R@ +REPLACE_SYMLINK = @REPLACE_SYMLINK@ +REPLACE_TIMEGM = @REPLACE_TIMEGM@ +REPLACE_TMPFILE = @REPLACE_TMPFILE@ +REPLACE_TRUNC = @REPLACE_TRUNC@ +REPLACE_TRUNCF = @REPLACE_TRUNCF@ +REPLACE_TRUNCL = @REPLACE_TRUNCL@ +REPLACE_TTYNAME_R = @REPLACE_TTYNAME_R@ +REPLACE_UNLINK = @REPLACE_UNLINK@ +REPLACE_UNLINKAT = @REPLACE_UNLINKAT@ +REPLACE_UNSETENV = @REPLACE_UNSETENV@ +REPLACE_USLEEP = @REPLACE_USLEEP@ +REPLACE_UTIMENSAT = @REPLACE_UTIMENSAT@ +REPLACE_VASPRINTF = @REPLACE_VASPRINTF@ +REPLACE_VDPRINTF = @REPLACE_VDPRINTF@ +REPLACE_VFPRINTF = @REPLACE_VFPRINTF@ +REPLACE_VPRINTF = @REPLACE_VPRINTF@ +REPLACE_VSNPRINTF = @REPLACE_VSNPRINTF@ +REPLACE_VSPRINTF = @REPLACE_VSPRINTF@ +REPLACE_WCRTOMB = @REPLACE_WCRTOMB@ +REPLACE_WCSNRTOMBS = @REPLACE_WCSNRTOMBS@ +REPLACE_WCSRTOMBS = @REPLACE_WCSRTOMBS@ +REPLACE_WCSWIDTH = @REPLACE_WCSWIDTH@ +REPLACE_WCTOB = @REPLACE_WCTOB@ +REPLACE_WCTOMB = @REPLACE_WCTOMB@ +REPLACE_WCWIDTH = @REPLACE_WCWIDTH@ +REPLACE_WRITE = @REPLACE_WRITE@ +SCHED_H = @SCHED_H@ +SET_MAKE = @SET_MAKE@ +SHELL = @SHELL@ +SIG_ATOMIC_T_SUFFIX = @SIG_ATOMIC_T_SUFFIX@ +SIZE_T_SUFFIX = @SIZE_T_SUFFIX@ +STDARG_H = @STDARG_H@ +STDBOOL_H = @STDBOOL_H@ +STDDEF_H = @STDDEF_H@ +STDINT_H = @STDINT_H@ +STRIP = @STRIP@ +SYS_TIME_H_DEFINES_STRUCT_TIMESPEC = @SYS_TIME_H_DEFINES_STRUCT_TIMESPEC@ +TIME_H_DEFINES_STRUCT_TIMESPEC = @TIME_H_DEFINES_STRUCT_TIMESPEC@ +UNDEFINE_STRTOK_R = @UNDEFINE_STRTOK_R@ +UNISTD_H_HAVE_WINSOCK2_H = @UNISTD_H_HAVE_WINSOCK2_H@ +UNISTD_H_HAVE_WINSOCK2_H_AND_USE_SOCKETS = @UNISTD_H_HAVE_WINSOCK2_H_AND_USE_SOCKETS@ +VERSION = @VERSION@ +WARN_CFLAGS = @WARN_CFLAGS@ +WCHAR_T_SUFFIX = @WCHAR_T_SUFFIX@ +WERROR_CFLAGS = @WERROR_CFLAGS@ +WINT_T_SUFFIX = @WINT_T_SUFFIX@ +abs_aux_dir = @abs_aux_dir@ +abs_builddir = @abs_builddir@ +abs_srcdir = @abs_srcdir@ +abs_top_builddir = @abs_top_builddir@ +abs_top_srcdir = @abs_top_srcdir@ +ac_ct_CC = @ac_ct_CC@ +ac_ct_CXX = @ac_ct_CXX@ +am__include = @am__include@ +am__leading_dot = @am__leading_dot@ +am__quote = @am__quote@ +am__tar = @am__tar@ +am__untar = @am__untar@ +bindir = @bindir@ +build = @build@ +build_alias = @build_alias@ +build_cpu = @build_cpu@ +build_os = @build_os@ +build_vendor = @build_vendor@ +builddir = @builddir@ +datadir = @datadir@ +datarootdir = @datarootdir@ +docdir = @docdir@ +dvidir = @dvidir@ +exec_prefix = @exec_prefix@ +host = @host@ +host_alias = @host_alias@ +host_cpu = @host_cpu@ +host_os = @host_os@ +host_vendor = @host_vendor@ +htmldir = 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Do not depend on +# built m4 executable, since not everyone has help2man or perl. +# Build the man page once in the srcdir, rather than in every VPATH build +# dir, to match how automake builds info pages. This is safe for 'make +# distcheck' since it is distributed pre-built. +$(srcdir)/m4.1: $(top_srcdir)/.version $(top_srcdir)/src/m4.c + @if test -x ../src/m4$(EXEEXT) ; then \ + echo "Updating man page m4.1" ; \ + $(HELP2MAN) --name="macro processor" --source='$(PACKAGE_STRING)' \ + --info-page=m4 --output=$@ ../src/m4$(EXEEXT) ; \ + else \ + echo "WARNING: The \`man' page \`$@' cannot be updated yet."; \ + echo " Retry once the program executable is ready."; \ + fi + +# Tell versions [3.59,3.63) of GNU make to not export all variables. +# Otherwise a system limit (for SysV at least) may be exceeded. +.NOEXPORT: diff --git a/doc/fdl-1.3.texi b/doc/fdl-1.3.texi new file mode 100644 index 00000000..fc19dddd --- /dev/null +++ b/doc/fdl-1.3.texi @@ -0,0 +1,506 @@ +@c The GNU Free Documentation License. +@center Version 1.3, 3 November 2008 + +@c This file is intended to be included within another document, +@c hence no sectioning command or @node. + +@display +Copyright @copyright{} 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. +@uref{http://fsf.org/} + +Everyone is permitted to copy and distribute verbatim copies +of this license document, but changing it is not allowed. +@end display + +@enumerate 0 +@item +PREAMBLE + +The purpose of this License is to make a manual, textbook, or other +functional and useful document @dfn{free} in the sense of freedom: to +assure everyone the effective freedom to copy and redistribute it, +with or without modifying it, either commercially or noncommercially. +Secondarily, this License preserves for the author and publisher a way +to get credit for their work, while not being considered responsible +for modifications made by others. + +This License is a kind of ``copyleft'', which means that derivative +works of the document must themselves be free in the same sense. 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The resulting work is called a ``modified version'' of +the earlier work or a work ``based on'' the earlier work. + +A ``covered work'' means either the unmodified Program or a work based +on the Program. + +To ``propagate'' a work means to do anything with it that, without +permission, would make you directly or secondarily liable for +infringement under applicable copyright law, except executing it on a +computer or modifying a private copy. Propagation includes copying, +distribution (with or without modification), making available to the +public, and in some countries other activities as well. + +To ``convey'' a work means any kind of propagation that enables other +parties to make or receive copies. Mere interaction with a user +through a computer network, with no transfer of a copy, is not +conveying. + +An interactive user interface displays ``Appropriate Legal Notices'' to +the extent that it includes a convenient and prominently visible +feature that (1) displays an appropriate copyright notice, and (2) +tells the user that there is no warranty for the work (except to the +extent that warranties are provided), that licensees may convey the +work under this License, and how to view a copy of this License. If +the interface presents a list of user commands or options, such as a +menu, a prominent item in the list meets this criterion. + +@item Source Code. + +The ``source code'' for a work means the preferred form of the work for +making modifications to it. ``Object code'' means any non-source form +of a work. + +A ``Standard Interface'' means an interface that either is an official +standard defined by a recognized standards body, or, in the case of +interfaces specified for a particular programming language, one that +is widely used among developers working in that language. + +The ``System Libraries'' of an executable work include anything, other +than the work as a whole, that (a) is included in the normal form of +packaging a Major Component, but which is not part of that Major +Component, and (b) serves only to enable use of the work with that +Major Component, or to implement a Standard Interface for which an +implementation is available to the public in source code form. A +``Major Component'', in this context, means a major essential component +(kernel, window system, and so on) of the specific operating system +(if any) on which the executable work runs, or a compiler used to +produce the work, or an object code interpreter used to run it. + +The ``Corresponding Source'' for a work in object code form means all +the source code needed to generate, install, and (for an executable +work) run the object code and to modify the work, including scripts to +control those activities. However, it does not include the work's +System Libraries, or general-purpose tools or generally available free +programs which are used unmodified in performing those activities but +which are not part of the work. 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This License acknowledges your +rights of fair use or other equivalent, as provided by copyright law. + +You may make, run and propagate covered works that you do not convey, +without conditions so long as your license otherwise remains in force. +You may convey covered works to others for the sole purpose of having +them make modifications exclusively for you, or provide you with +facilities for running those works, provided that you comply with the +terms of this License in conveying all material for which you do not +control copyright. Those thus making or running the covered works for +you must do so exclusively on your behalf, under your direction and +control, on terms that prohibit them from making any copies of your +copyrighted material outside their relationship with you. + +Conveying under any other circumstances is permitted solely under the +conditions stated below. Sublicensing is not allowed; section 10 +makes it unnecessary. + +@item Protecting Users' Legal Rights From Anti-Circumvention Law. + +No covered work shall be deemed part of an effective technological +measure under any applicable law fulfilling obligations under article +11 of the WIPO copyright treaty adopted on 20 December 1996, or +similar laws prohibiting or restricting circumvention of such +measures. + +When you convey a covered work, you waive any legal power to forbid +circumvention of technological measures to the extent such +circumvention is effected by exercising rights under this License with +respect to the covered work, and you disclaim any intention to limit +operation or modification of the work as a means of enforcing, against +the work's users, your or third parties' legal rights to forbid +circumvention of technological measures. + +@item Conveying Verbatim Copies. + +You may convey verbatim copies of the Program's source code as you +receive it, in any medium, provided that you conspicuously and +appropriately publish on each copy an appropriate copyright notice; +keep intact all notices stating that this License and any +non-permissive terms added in accord with section 7 apply to the code; +keep intact all notices of the absence of any warranty; and give all +recipients a copy of this License along with the Program. + +You may charge any price or no price for each copy that you convey, +and you may offer support or warranty protection for a fee. + +@item Conveying Modified Source Versions. + +You may convey a work based on the Program, or the modifications to +produce it from the Program, in the form of source code under the +terms of section 4, provided that you also meet all of these +conditions: + +@enumerate a +@item +The work must carry prominent notices stating that you modified it, +and giving a relevant date. + +@item +The work must carry prominent notices stating that it is released +under this License and any conditions added under section 7. This +requirement modifies the requirement in section 4 to ``keep intact all +notices''. + +@item +You must license the entire work, as a whole, under this License to +anyone who comes into possession of a copy. This License will +therefore apply, along with any applicable section 7 additional terms, +to the whole of the work, and all its parts, regardless of how they +are packaged. This License gives no permission to license the work in +any other way, but it does not invalidate such permission if you have +separately received it. + +@item +If the work has interactive user interfaces, each must display +Appropriate Legal Notices; however, if the Program has interactive +interfaces that do not display Appropriate Legal Notices, your work +need not make them do so. +@end enumerate + +A compilation of a covered work with other separate and independent +works, which are not by their nature extensions of the covered work, +and which are not combined with it such as to form a larger program, +in or on a volume of a storage or distribution medium, is called an +``aggregate'' if the compilation and its resulting copyright are not +used to limit the access or legal rights of the compilation's users +beyond what the individual works permit. Inclusion of a covered work +in an aggregate does not cause this License to apply to the other +parts of the aggregate. + +@item Conveying Non-Source Forms. + +You may convey a covered work in object code form under the terms of +sections 4 and 5, provided that you also convey the machine-readable +Corresponding Source under the terms of this License, in one of these +ways: + +@enumerate a +@item +Convey the object code in, or embodied in, a physical product +(including a physical distribution medium), accompanied by the +Corresponding Source fixed on a durable physical medium customarily +used for software interchange. + +@item +Convey the object code in, or embodied in, a physical product +(including a physical distribution medium), accompanied by a written +offer, valid for at least three years and valid for as long as you +offer spare parts or customer support for that product model, to give +anyone who possesses the object code either (1) a copy of the +Corresponding Source for all the software in the product that is +covered by this License, on a durable physical medium customarily used +for software interchange, for a price no more than your reasonable +cost of physically performing this conveying of source, or (2) access +to copy the Corresponding Source from a network server at no charge. + +@item +Convey individual copies of the object code with a copy of the written +offer to provide the Corresponding Source. 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If additional permissions +apply only to part of the Program, that part may be used separately +under those permissions, but the entire Program remains governed by +this License without regard to the additional permissions. + +When you convey a copy of a covered work, you may at your option +remove any additional permissions from that copy, or from any part of +it. (Additional permissions may be written to require their own +removal in certain cases when you modify the work.) You may place +additional permissions on material, added by you to a covered work, +for which you have or can give appropriate copyright permission. + +Notwithstanding any other provision of this License, for material you +add to a covered work, you may (if authorized by the copyright holders +of that material) supplement the terms of this License with terms: + +@enumerate a +@item +Disclaiming warranty or limiting liability differently from the terms +of sections 15 and 16 of this License; or + +@item +Requiring preservation of specified reasonable legal notices or author +attributions in that material or in the Appropriate Legal Notices +displayed by works containing it; or + +@item +Prohibiting misrepresentation of the origin of that material, or +requiring that modified versions of such material be marked in +reasonable ways as different from the original version; or + +@item +Limiting the use for publicity purposes of names of licensors or +authors of the material; or + +@item +Declining to grant rights under trademark law for use of some trade +names, trademarks, or service marks; or + +@item +Requiring indemnification of licensors and authors of that material by +anyone who conveys the material (or modified versions of it) with +contractual assumptions of liability to the recipient, for any +liability that these contractual assumptions directly impose on those +licensors and authors. +@end enumerate + +All other non-permissive additional terms are considered ``further +restrictions'' within the meaning of section 10. If the Program as you +received it, or any part of it, contains a notice stating that it is +governed by this License along with a term that is a further +restriction, you may remove that term. If a license document contains +a further restriction but permits relicensing or conveying under this +License, you may add to a covered work material governed by the terms +of that license document, provided that the further restriction does +not survive such relicensing or conveying. + +If you add terms to a covered work in accord with this section, you +must place, in the relevant source files, a statement of the +additional terms that apply to those files, or a notice indicating +where to find the applicable terms. + +Additional terms, permissive or non-permissive, may be stated in the +form of a separately written license, or stated as exceptions; the +above requirements apply either way. + +@item Termination. + +You may not propagate or modify a covered work except as expressly +provided under this License. Any attempt otherwise to propagate or +modify it is void, and will automatically terminate your rights under +this License (including any patent licenses granted under the third +paragraph of section 11). + +However, if you cease all violation of this License, then your license +from a particular copyright holder is reinstated (a) provisionally, +unless and until the copyright holder explicitly and finally +terminates your license, and (b) permanently, if the copyright holder +fails to notify you of the violation by some reasonable means prior to +60 days after the cessation. + +Moreover, your license from a particular copyright holder is +reinstated permanently if the copyright holder notifies you of the +violation by some reasonable means, this is the first time you have +received notice of violation of this License (for any work) from that +copyright holder, and you cure the violation prior to 30 days after +your receipt of the notice. + +Termination of your rights under this section does not terminate the +licenses of parties who have received copies or rights from you under +this License. If your rights have been terminated and not permanently +reinstated, you do not qualify to receive new licenses for the same +material under section 10. + +@item Acceptance Not Required for Having Copies. + +You are not required to accept this License in order to receive or run +a copy of the Program. Ancillary propagation of a covered work +occurring solely as a consequence of using peer-to-peer transmission +to receive a copy likewise does not require acceptance. However, +nothing other than this License grants you permission to propagate or +modify any covered work. These actions infringe copyright if you do +not accept this License. Therefore, by modifying or propagating a +covered work, you indicate your acceptance of this License to do so. + +@item Automatic Licensing of Downstream Recipients. + +Each time you convey a covered work, the recipient automatically +receives a license from the original licensors, to run, modify and +propagate that work, subject to this License. You are not responsible +for enforcing compliance by third parties with this License. + +An ``entity transaction'' is a transaction transferring control of an +organization, or substantially all assets of one, or subdividing an +organization, or merging organizations. If propagation of a covered +work results from an entity transaction, each party to that +transaction who receives a copy of the work also receives whatever +licenses to the work the party's predecessor in interest had or could +give under the previous paragraph, plus a right to possession of the +Corresponding Source of the work from the predecessor in interest, if +the predecessor has it or can get it with reasonable efforts. + +You may not impose any further restrictions on the exercise of the +rights granted or affirmed under this License. For example, you may +not impose a license fee, royalty, or other charge for exercise of +rights granted under this License, and you may not initiate litigation +(including a cross-claim or counterclaim in a lawsuit) alleging that +any patent claim is infringed by making, using, selling, offering for +sale, or importing the Program or any portion of it. + +@item Patents. + +A ``contributor'' is a copyright holder who authorizes use under this +License of the Program or a work on which the Program is based. The +work thus licensed is called the contributor's ``contributor version''. + +A contributor's ``essential patent claims'' are all patent claims owned +or controlled by the contributor, whether already acquired or +hereafter acquired, that would be infringed by some manner, permitted +by this License, of making, using, or selling its contributor version, +but do not include claims that would be infringed only as a +consequence of further modification of the contributor version. For +purposes of this definition, ``control'' includes the right to grant +patent sublicenses in a manner consistent with the requirements of +this License. + +Each contributor grants you a non-exclusive, worldwide, royalty-free +patent license under the contributor's essential patent claims, to +make, use, sell, offer for sale, import and otherwise run, modify and +propagate the contents of its contributor version. + +In the following three paragraphs, a ``patent license'' is any express +agreement or commitment, however denominated, not to enforce a patent +(such as an express permission to practice a patent or covenant not to +sue for patent infringement). To ``grant'' such a patent license to a +party means to make such an agreement or commitment not to enforce a +patent against the party. + +If you convey a covered work, knowingly relying on a patent license, +and the Corresponding Source of the work is not available for anyone +to copy, free of charge and under the terms of this License, through a +publicly available network server or other readily accessible means, +then you must either (1) cause the Corresponding Source to be so +available, or (2) arrange to deprive yourself of the benefit of the +patent license for this particular work, or (3) arrange, in a manner +consistent with the requirements of this License, to extend the patent +license to downstream recipients. ``Knowingly relying'' means you have +actual knowledge that, but for the patent license, your conveying the +covered work in a country, or your recipient's use of the covered work +in a country, would infringe one or more identifiable patents in that +country that you have reason to believe are valid. + +If, pursuant to or in connection with a single transaction or +arrangement, you convey, or propagate by procuring conveyance of, a +covered work, and grant a patent license to some of the parties +receiving the covered work authorizing them to use, propagate, modify +or convey a specific copy of the covered work, then the patent license +you grant is automatically extended to all recipients of the covered +work and works based on it. + +A patent license is ``discriminatory'' if it does not include within the +scope of its coverage, prohibits the exercise of, or is conditioned on +the non-exercise of one or more of the rights that are specifically +granted under this License. You may not convey a covered work if you +are a party to an arrangement with a third party that is in the +business of distributing software, under which you make payment to the +third party based on the extent of your activity of conveying the +work, and under which the third party grants, to any of the parties +who would receive the covered work from you, a discriminatory patent +license (a) in connection with copies of the covered work conveyed by +you (or copies made from those copies), or (b) primarily for and in +connection with specific products or compilations that contain the +covered work, unless you entered into that arrangement, or that patent +license was granted, prior to 28 March 2007. + +Nothing in this License shall be construed as excluding or limiting +any implied license or other defenses to infringement that may +otherwise be available to you under applicable patent law. + +@item No Surrender of Others' Freedom. + +If conditions are imposed on you (whether by court order, agreement or +otherwise) that contradict the conditions of this License, they do not +excuse you from the conditions of this License. If you cannot convey +a covered work so as to satisfy simultaneously your obligations under +this License and any other pertinent obligations, then as a +consequence you may not convey it at all. For example, if you agree +to terms that obligate you to collect a royalty for further conveying +from those to whom you convey the Program, the only way you could +satisfy both those terms and this License would be to refrain entirely +from conveying the Program. + +@item Use with the GNU Affero General Public License. + +Notwithstanding any other provision of this License, you have +permission to link or combine any covered work with a work licensed +under version 3 of the GNU Affero General Public License into a single +combined work, and to convey the resulting work. The terms of this +License will continue to apply to the part which is the covered work, +but the special requirements of the GNU Affero General Public License, +section 13, concerning interaction through a network will apply to the +combination as such. + +@item Revised Versions of this License. + +The Free Software Foundation may publish revised and/or new versions +of the GNU General Public License from time to time. Such new +versions will be similar in spirit to the present version, but may +differ in detail to address new problems or concerns. + +Each version is given a distinguishing version number. If the Program +specifies that a certain numbered version of the GNU General Public +License ``or any later version'' applies to it, you have the option of +following the terms and conditions either of that numbered version or +of any later version published by the Free Software Foundation. If +the Program does not specify a version number of the GNU General +Public License, you may choose any version ever published by the Free +Software Foundation. + +If the Program specifies that a proxy can decide which future versions +of the GNU General Public License can be used, that proxy's public +statement of acceptance of a version permanently authorizes you to +choose that version for the Program. + +Later license versions may give you additional or different +permissions. However, no additional obligations are imposed on any +author or copyright holder as a result of your choosing to follow a +later version. + +@item Disclaimer of Warranty. + +THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY +APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT +HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM ``AS IS'' WITHOUT +WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT +LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND +PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE +DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR +CORRECTION. + +@item Limitation of Liability. + +IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING +WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR +CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, +INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES +ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT +NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR +LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM +TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER +PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. + +@item Interpretation of Sections 15 and 16. + +If the disclaimer of warranty and limitation of liability provided +above cannot be given local legal effect according to their terms, +reviewing courts shall apply local law that most closely approximates +an absolute waiver of all civil liability in connection with the +Program, unless a warranty or assumption of liability accompanies a +copy of the Program in return for a fee. + +@end enumerate + +@heading END OF TERMS AND CONDITIONS + +@heading How to Apply These Terms to Your New Programs + +If you develop a new program, and you want it to be of the greatest +possible use to the public, the best way to achieve this is to make it +free software which everyone can redistribute and change under these +terms. + +To do so, attach the following notices to the program. It is safest +to attach them to the start of each source file to most effectively +state the exclusion of warranty; and each file should have at least +the ``copyright'' line and a pointer to where the full notice is found. + +@smallexample +@var{one line to give the program's name and a brief idea of what it does.} +Copyright (C) @var{year} @var{name of author} + +This program is free software: you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation, either version 3 of the License, or (at +your option) any later version. + +This program is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with this program. If not, see @url{http://www.gnu.org/licenses/}. +@end smallexample + +Also add information on how to contact you by electronic and paper mail. + +If the program does terminal interaction, make it output a short +notice like this when it starts in an interactive mode: + +@smallexample +@var{program} Copyright (C) @var{year} @var{name of author} +This program comes with ABSOLUTELY NO WARRANTY; for details type @samp{show w}. +This is free software, and you are welcome to redistribute it +under certain conditions; type @samp{show c} for details. +@end smallexample + +The hypothetical commands @samp{show w} and @samp{show c} should show +the appropriate parts of the General Public License. Of course, your +program's commands might be different; for a GUI interface, you would +use an ``about box''. + +You should also get your employer (if you work as a programmer) or school, +if any, to sign a ``copyright disclaimer'' for the program, if necessary. +For more information on this, and how to apply and follow the GNU GPL, see +@url{http://www.gnu.org/licenses/}. + +The GNU General Public License does not permit incorporating your +program into proprietary programs. If your program is a subroutine +library, you may consider it more useful to permit linking proprietary +applications with the library. If this is what you want to do, use +the GNU Lesser General Public License instead of this License. But +first, please read @url{http://www.gnu.org/philosophy/why-not-lgpl.html}. diff --git a/doc/m4.1 b/doc/m4.1 new file mode 100644 index 00000000..63fbd8e8 --- /dev/null +++ b/doc/m4.1 @@ -0,0 +1,151 @@ +.\" DO NOT MODIFY THIS FILE! It was generated by help2man 1.38.2. +.TH M4 "1" "March 2011" "GNU M4 1.4.16" "User Commands" +.SH NAME +m4 \- macro processor +.SH SYNOPSIS +.B m4 +[\fIOPTION\fR]... [\fIFILE\fR]... +.SH DESCRIPTION +Process macros in FILEs. If no FILE or if FILE is `\-', standard input +is read. +.PP +Mandatory or optional arguments to long options are mandatory or optional +for short options too. +.SS "Operation modes:" +.TP +\fB\-\-help\fR +display this help and exit +.TP +\fB\-\-version\fR +output version information and exit +.TP +\fB\-E\fR, \fB\-\-fatal\-warnings\fR +once: warnings become errors, twice: stop +execution at first error +.TP +\fB\-i\fR, \fB\-\-interactive\fR +unbuffer output, ignore interrupts +.TP +\fB\-P\fR, \fB\-\-prefix\-builtins\fR +force a `m4_' prefix to all builtins +.TP +\fB\-Q\fR, \fB\-\-quiet\fR, \fB\-\-silent\fR +suppress some warnings for builtins +.TP +\fB\-\-warn\-macro\-sequence\fR[=\fIREGEXP\fR] +warn if macro definition matches REGEXP, +.IP +default \e$\e({[^}]*}\e|[0\-9][0\-9]+\e) +.SS "Preprocessor features:" +.TP +\fB\-D\fR, \fB\-\-define=NAME\fR[=\fIVALUE\fR] +define NAME as having VALUE, or empty +.TP +\fB\-I\fR, \fB\-\-include\fR=\fIDIRECTORY\fR +append DIRECTORY to include path +.TP +\fB\-s\fR, \fB\-\-synclines\fR +generate `#line NUM "FILE"' lines +.TP +\fB\-U\fR, \fB\-\-undefine\fR=\fINAME\fR +undefine NAME +.SS "Limits control:" +.TP +\fB\-g\fR, \fB\-\-gnu\fR +override \fB\-G\fR to re\-enable GNU extensions +.TP +\fB\-G\fR, \fB\-\-traditional\fR +suppress all GNU extensions +.TP +\fB\-H\fR, \fB\-\-hashsize\fR=\fIPRIME\fR +set symbol lookup hash table size [509] +.TP +\fB\-L\fR, \fB\-\-nesting\-limit\fR=\fINUMBER\fR +change nesting limit, 0 for unlimited [0] +.SS "Frozen state files:" +.TP +\fB\-F\fR, \fB\-\-freeze\-state\fR=\fIFILE\fR +produce a frozen state on FILE at end +.TP +\fB\-R\fR, \fB\-\-reload\-state\fR=\fIFILE\fR +reload a frozen state from FILE at start +.SS "Debugging:" +.TP +\fB\-d\fR, \fB\-\-debug\fR[=\fIFLAGS\fR] +set debug level (no FLAGS implies `aeq') +.TP +\fB\-\-debugfile\fR[=\fIFILE\fR] +redirect debug and trace output to FILE +(default stderr, discard if empty string) +.TP +\fB\-l\fR, \fB\-\-arglength\fR=\fINUM\fR +restrict macro tracing size +.TP +\fB\-t\fR, \fB\-\-trace\fR=\fINAME\fR +trace NAME when it is defined +.SS "FLAGS is any of:" +.TP +a +show actual arguments +.TP +c +show before collect, after collect and after call +.TP +e +show expansion +.TP +f +say current input file name +.TP +i +show changes in input files +.TP +l +say current input line number +.TP +p +show results of path searches +.TP +q +quote values as necessary, with a or e flag +.TP +t +trace for all macro calls, not only traceon'ed +.TP +x +add a unique macro call id, useful with c flag +.TP +V +shorthand for all of the above flags +.PP +If defined, the environment variable `M4PATH' is a colon\-separated list +of directories included after any specified by `\-I'. +.PP +Exit status is 0 for success, 1 for failure, 63 for frozen file version +mismatch, or whatever value was passed to the m4exit macro. +.SH AUTHOR +Written by Rene' Seindal. +.SH "REPORTING BUGS" +Report bugs to: bug\-m4@gnu.org +.br +GNU M4 home page: <http://www.gnu.org/software/m4/> +.br +General help using GNU software: <http://www.gnu.org/gethelp/> +.SH COPYRIGHT +Copyright \(co 2011 Free Software Foundation, Inc. +License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>. +.br +This is free software: you are free to change and redistribute it. +There is NO WARRANTY, to the extent permitted by law. +.SH "SEE ALSO" +The full documentation for +.B m4 +is maintained as a Texinfo manual. If the +.B info +and +.B m4 +programs are properly installed at your site, the command +.IP +.B info m4 +.PP +should give you access to the complete manual. diff --git a/doc/m4.info b/doc/m4.info new file mode 100644 index 00000000..8c81aa7c --- /dev/null +++ b/doc/m4.info @@ -0,0 +1,134 @@ +This is m4.info, produced by makeinfo version 4.13 from m4.texinfo. + +This manual (28 February 2011) is for GNU M4 (version 1.4.16), a +package containing an implementation of the m4 macro language. + + Copyright (C) 1989-1994, 2004-2011 Free Software Foundation, Inc. + + Permission is granted to copy, distribute and/or modify this + document under the terms of the GNU Free Documentation License, + Version 1.3 or any later version published by the Free Software + Foundation; with no Invariant Sections, no Front-Cover Texts, and + no Back-Cover Texts. A copy of the license is included in the + section entitled "GNU Free Documentation License." + +INFO-DIR-SECTION Text creation and manipulation +START-INFO-DIR-ENTRY +* M4: (m4). A powerful macro processor. +END-INFO-DIR-ENTRY + + +Indirect: +m4.info-1: 817 +m4.info-2: 300465 + +Tag Table: +(Indirect) +Node: Top817 +Node: Preliminaries9625 +Node: Intro10311 +Node: History11943 +Node: Bugs14789 +Node: Manual16040 +Node: Invoking m419438 +Node: Operation modes21584 +Node: Preprocessor features24556 +Node: Limits control27653 +Node: Frozen state31555 +Node: Debugging options32354 +Node: Command line files34338 +Node: Syntax35911 +Node: Names37030 +Node: Quoted strings37492 +Node: Comments38141 +Node: Other tokens39018 +Node: Input processing39596 +Ref: Input processing-Footnote-147517 +Node: Macros47712 +Node: Invocation48206 +Node: Inhibiting Invocation49007 +Node: Macro Arguments53138 +Node: Quoting Arguments56200 +Node: Macro expansion58323 +Node: Definitions59024 +Node: Define59809 +Node: Arguments62247 +Node: Pseudo Arguments65919 +Node: Undefine69461 +Node: Defn70591 +Node: Pushdef75041 +Node: Indir77667 +Node: Builtin79795 +Node: Conditionals82021 +Node: Ifdef82963 +Node: Ifelse83826 +Node: Shift87144 +Node: Forloop97693 +Node: Foreach100329 +Node: Stacks105817 +Node: Composition108856 +Node: Debugging114796 +Node: Dumpdef115381 +Node: Trace116791 +Node: Debug Levels120364 +Node: Debug Output125068 +Node: Input Control126352 +Node: Dnl126889 +Node: Changequote128790 +Node: Changecom134887 +Node: Changeword138583 +Node: M4wrap144024 +Node: File Inclusion148020 +Node: Include148337 +Node: Search Path151048 +Node: Diversions151965 +Node: Divert153648 +Node: Undivert156174 +Node: Divnum159497 +Node: Cleardivert159961 +Node: Text handling161166 +Node: Len161889 +Node: Index macro162274 +Node: Regexp163147 +Node: Substr165686 +Node: Translit166737 +Node: Patsubst169459 +Node: Format173985 +Node: Arithmetic177178 +Node: Incr177627 +Node: Eval178402 +Node: Shell commands186365 +Node: Platform macros187287 +Node: Syscmd189402 +Node: Esyscmd191682 +Node: Sysval193191 +Node: Mkstemp194873 +Node: Miscellaneous198828 +Node: Errprint199261 +Node: Location200480 +Node: M4exit203254 +Node: Frozen files205341 +Node: Using frozen files206122 +Node: Frozen file format209386 +Node: Compatibility212450 +Node: Extensions213516 +Node: Incompatibilities217383 +Node: Other Incompatibilities226309 +Node: Answers228955 +Node: Improved exch229737 +Node: Improved forloop230275 +Node: Improved foreach235607 +Node: Improved copy248624 +Node: Improved m4wrap252578 +Node: Improved cleardivert255002 +Node: Improved capitalize255983 +Node: Improved fatal_error260846 +Node: Copying This Package261907 +Node: GNU General Public License262386 +Node: Copying This Manual299945 +Node: GNU Free Documentation License300465 +Node: Indices325596 +Node: Macro index325876 +Node: Concept index332113 + +End Tag Table diff --git a/doc/m4.info-1 b/doc/m4.info-1 new file mode 100644 index 00000000..e1a61385 --- /dev/null +++ b/doc/m4.info-1 @@ -0,0 +1,7858 @@ +This is m4.info, produced by makeinfo version 4.13 from m4.texinfo. + +This manual (28 February 2011) is for GNU M4 (version 1.4.16), a +package containing an implementation of the m4 macro language. + + Copyright (C) 1989-1994, 2004-2011 Free Software Foundation, Inc. + + Permission is granted to copy, distribute and/or modify this + document under the terms of the GNU Free Documentation License, + Version 1.3 or any later version published by the Free Software + Foundation; with no Invariant Sections, no Front-Cover Texts, and + no Back-Cover Texts. A copy of the license is included in the + section entitled "GNU Free Documentation License." + +INFO-DIR-SECTION Text creation and manipulation +START-INFO-DIR-ENTRY +* M4: (m4). A powerful macro processor. +END-INFO-DIR-ENTRY + + +File: m4.info, Node: Top, Next: Preliminaries, Up: (dir) + +GNU M4 +****** + +This manual (28 February 2011) is for GNU M4 (version 1.4.16), a +package containing an implementation of the m4 macro language. + + Copyright (C) 1989-1994, 2004-2011 Free Software Foundation, Inc. + + Permission is granted to copy, distribute and/or modify this + document under the terms of the GNU Free Documentation License, + Version 1.3 or any later version published by the Free Software + Foundation; with no Invariant Sections, no Front-Cover Texts, and + no Back-Cover Texts. A copy of the license is included in the + section entitled "GNU Free Documentation License." + + GNU `m4' is an implementation of the traditional UNIX macro +processor. It is mostly SVR4 compatible, although it has some +extensions (for example, handling more than 9 positional parameters to +macros). `m4' also has builtin functions for including files, running +shell commands, doing arithmetic, etc. Autoconf needs GNU `m4' for +generating `configure' scripts, but not for running them. + + GNU `m4' was originally written by Rene' Seindal, with subsequent +changes by Franc,ois Pinard and other volunteers on the Internet. All +names and email addresses can be found in the files `m4-1.4.16/AUTHORS' +and `m4-1.4.16/THANKS' from the GNU M4 distribution. + + This is release 1.4.16. It is now considered stable: future +releases in the 1.4.x series are only meant to fix bugs, increase speed, +or improve documentation. However... + + An experimental feature, which would improve `m4' usefulness, allows +for changing the syntax for what is a "word" in `m4'. You should use: + ./configure --enable-changeword + if you want this feature compiled in. The current implementation +slows down `m4' considerably and is hardly acceptable. In the future, +`m4' 2.0 will come with a different set of new features that provide +similar capabilities, but without the inefficiencies, so changeword +will go away and _you should not count on it_. + +* Menu: + +* Preliminaries:: Introduction and preliminaries +* Invoking m4:: Invoking `m4' +* Syntax:: Lexical and syntactic conventions + +* Macros:: How to invoke macros +* Definitions:: How to define new macros +* Conditionals:: Conditionals, loops, and recursion + +* Debugging:: How to debug macros and input + +* Input Control:: Input control +* File Inclusion:: File inclusion +* Diversions:: Diverting and undiverting output + +* Text handling:: Macros for text handling +* Arithmetic:: Macros for doing arithmetic +* Shell commands:: Macros for running shell commands +* Miscellaneous:: Miscellaneous builtin macros +* Frozen files:: Fast loading of frozen state + +* Compatibility:: Compatibility with other versions of `m4' +* Answers:: Correct version of some examples + +* Copying This Package:: How to make copies of the overall M4 package +* Copying This Manual:: How to make copies of this manual +* Indices:: Indices of concepts and macros + + --- The Detailed Node Listing --- + +Introduction and preliminaries + +* Intro:: Introduction to `m4' +* History:: Historical references +* Bugs:: Problems and bugs +* Manual:: Using this manual + +Invoking `m4' + +* Operation modes:: Command line options for operation modes +* Preprocessor features:: Command line options for preprocessor features +* Limits control:: Command line options for limits control +* Frozen state:: Command line options for frozen state +* Debugging options:: Command line options for debugging +* Command line files:: Specifying input files on the command line + +Lexical and syntactic conventions + +* Names:: Macro names +* Quoted strings:: Quoting input to `m4' +* Comments:: Comments in `m4' input +* Other tokens:: Other kinds of input tokens +* Input processing:: How `m4' copies input to output + +How to invoke macros + +* Invocation:: Macro invocation +* Inhibiting Invocation:: Preventing macro invocation +* Macro Arguments:: Macro arguments +* Quoting Arguments:: On Quoting Arguments to macros +* Macro expansion:: Expanding macros + +How to define new macros + +* Define:: Defining a new macro +* Arguments:: Arguments to macros +* Pseudo Arguments:: Special arguments to macros +* Undefine:: Deleting a macro +* Defn:: Renaming macros +* Pushdef:: Temporarily redefining macros + +* Indir:: Indirect call of macros +* Builtin:: Indirect call of builtins + +Conditionals, loops, and recursion + +* Ifdef:: Testing if a macro is defined +* Ifelse:: If-else construct, or multibranch +* Shift:: Recursion in `m4' +* Forloop:: Iteration by counting +* Foreach:: Iteration by list contents +* Stacks:: Working with definition stacks +* Composition:: Building macros with macros + +How to debug macros and input + +* Dumpdef:: Displaying macro definitions +* Trace:: Tracing macro calls +* Debug Levels:: Controlling debugging output +* Debug Output:: Saving debugging output + +Input control + +* Dnl:: Deleting whitespace in input +* Changequote:: Changing the quote characters +* Changecom:: Changing the comment delimiters +* Changeword:: Changing the lexical structure of words +* M4wrap:: Saving text until end of input + +File inclusion + +* Include:: Including named files +* Search Path:: Searching for include files + +Diverting and undiverting output + +* Divert:: Diverting output +* Undivert:: Undiverting output +* Divnum:: Diversion numbers +* Cleardivert:: Discarding diverted text + +Macros for text handling + +* Len:: Calculating length of strings +* Index macro:: Searching for substrings +* Regexp:: Searching for regular expressions +* Substr:: Extracting substrings +* Translit:: Translating characters +* Patsubst:: Substituting text by regular expression +* Format:: Formatting strings (printf-like) + +Macros for doing arithmetic + +* Incr:: Decrement and increment operators +* Eval:: Evaluating integer expressions + +Macros for running shell commands + +* Platform macros:: Determining the platform +* Syscmd:: Executing simple commands +* Esyscmd:: Reading the output of commands +* Sysval:: Exit status +* Mkstemp:: Making temporary files + +Miscellaneous builtin macros + +* Errprint:: Printing error messages +* Location:: Printing current location +* M4exit:: Exiting from `m4' + +Fast loading of frozen state + +* Using frozen files:: Using frozen files +* Frozen file format:: Frozen file format + +Compatibility with other versions of `m4' + +* Extensions:: Extensions in GNU M4 +* Incompatibilities:: Facilities in System V m4 not in GNU M4 +* Other Incompatibilities:: Other incompatibilities + +Correct version of some examples + +* Improved exch:: Solution for `exch' +* Improved forloop:: Solution for `forloop' +* Improved foreach:: Solution for `foreach' +* Improved copy:: Solution for `copy' +* Improved m4wrap:: Solution for `m4wrap' +* Improved cleardivert:: Solution for `cleardivert' +* Improved capitalize:: Solution for `capitalize' +* Improved fatal_error:: Solution for `fatal_error' + +How to make copies of the overall M4 package + +* GNU General Public License:: License for copying the M4 package + +How to make copies of this manual + +* GNU Free Documentation License:: License for copying this manual + +Indices of concepts and macros + +* Macro index:: Index for all `m4' macros +* Concept index:: Index for many concepts + + +File: m4.info, Node: Preliminaries, Next: Invoking m4, Prev: Top, Up: Top + +1 Introduction and preliminaries +******************************** + +This first chapter explains what GNU `m4' is, where `m4' comes from, +how to read and use this documentation, how to call the `m4' program, +and how to report bugs about it. It concludes by giving tips for +reading the remainder of the manual. + + The following chapters then detail all the features of the `m4' +language. + +* Menu: + +* Intro:: Introduction to `m4' +* History:: Historical references +* Bugs:: Problems and bugs +* Manual:: Using this manual + + +File: m4.info, Node: Intro, Next: History, Up: Preliminaries + +1.1 Introduction to `m4' +======================== + +`m4' is a macro processor, in the sense that it copies its input to the +output, expanding macros as it goes. Macros are either builtin or +user-defined, and can take any number of arguments. Besides just doing +macro expansion, `m4' has builtin functions for including named files, +running shell commands, doing integer arithmetic, manipulating text in +various ways, performing recursion, etc.... `m4' can be used either as +a front-end to a compiler, or as a macro processor in its own right. + + The `m4' macro processor is widely available on all UNIXes, and has +been standardized by POSIX. Usually, only a small percentage of users +are aware of its existence. However, those who find it often become +committed users. The popularity of GNU Autoconf, which requires GNU +`m4' for _generating_ `configure' scripts, is an incentive for many to +install it, while these people will not themselves program in `m4'. +GNU `m4' is mostly compatible with the System V, Release 3 version, +except for some minor differences. *Note Compatibility::, for more +details. + + Some people find `m4' to be fairly addictive. They first use `m4' +for simple problems, then take bigger and bigger challenges, learning +how to write complex sets of `m4' macros along the way. Once really +addicted, users pursue writing of sophisticated `m4' applications even +to solve simple problems, devoting more time debugging their `m4' +scripts than doing real work. Beware that `m4' may be dangerous for +the health of compulsive programmers. + + +File: m4.info, Node: History, Next: Bugs, Prev: Intro, Up: Preliminaries + +1.2 Historical references +========================= + +`GPM' was an important ancestor of `m4'. See C. Strachey: "A General +Purpose Macro generator", Computer Journal 8,3 (1965), pp. 225 ff. +`GPM' is also succinctly described into David Gries classic "Compiler +Construction for Digital Computers". + + The classic B. Kernighan and P.J. Plauger: "Software Tools", +Addison-Wesley, Inc. (1976) describes and implements a Unix +macro-processor language, which inspired Dennis Ritchie to write `m3', +a macro processor for the AP-3 minicomputer. + + Kernighan and Ritchie then joined forces to develop the original +`m4', as described in "The M4 Macro Processor", Bell Laboratories +(1977). It had only 21 builtin macros. + + While `GPM' was more _pure_, `m4' is meant to deal with the true +intricacies of real life: macros can be recognized without being +pre-announced, skipping whitespace or end-of-lines is easier, more +constructs are builtin instead of derived, etc. + + Originally, the Kernighan and Plauger macro-processor, and then +`m3', formed the engine for the Rational FORTRAN preprocessor, that is, +the `Ratfor' equivalent of `cpp'. Later, `m4' was used as a front-end +for `Ratfor', `C' and `Cobol'. + + Rene' Seindal released his implementation of `m4', GNU `m4', in +1990, with the aim of removing the artificial limitations in many of +the traditional `m4' implementations, such as maximum line length, +macro size, or number of macros. + + The late Professor A. Dain Samples described and implemented a +further evolution in the form of `M5': "User's Guide to the M5 Macro +Language: 2nd edition", Electronic Announcement on comp.compilers +newsgroup (1992). + + Franc,ois Pinard took over maintenance of GNU `m4' in 1992, until +1994 when he released GNU `m4' 1.4, which was the stable release for 10 +years. It was at this time that GNU Autoconf decided to require GNU +`m4' as its underlying engine, since all other implementations of `m4' +had too many limitations. + + More recently, in 2004, Paul Eggert released 1.4.1 and 1.4.2 which +addressed some long standing bugs in the venerable 1.4 release. Then in +2005, Gary V. Vaughan collected together the many patches to GNU `m4' +1.4 that were floating around the net and released 1.4.3 and 1.4.4. +And in 2006, Eric Blake joined the team and prepared patches for the +release of 1.4.5, 1.4.6, 1.4.7, and 1.4.8. More bug fixes were +incorporated in 2007, with releases 1.4.9 and 1.4.10. Eric continued +with some portability fixes for 1.4.11 and 1.4.12 in 2008, 1.4.13 in +2009, 1.4.14 and 1.4.15 in 2010, and 1.4.16 in 2011. + + Meanwhile, development has continued on new features for `m4', such +as dynamic module loading and additional builtins. When complete, GNU +`m4' 2.0 will start a new series of releases. + + +File: m4.info, Node: Bugs, Next: Manual, Prev: History, Up: Preliminaries + +1.3 Problems and bugs +===================== + +If you have problems with GNU M4 or think you've found a bug, please +report it. Before reporting a bug, make sure you've actually found a +real bug. Carefully reread the documentation and see if it really says +you can do what you're trying to do. If it's not clear whether you +should be able to do something or not, report that too; it's a bug in +the documentation! + + Before reporting a bug or trying to fix it yourself, try to isolate +it to the smallest possible input file that reproduces the problem. +Then send us the input file and the exact results `m4' gave you. Also +say what you expected to occur; this will help us decide whether the +problem was really in the documentation. + + Once you've got a precise problem, send e-mail to <bug-m4@gnu.org>. +Please include the version number of `m4' you are using. You can get +this information with the command `m4 --version'. Also provide details +about the platform you are executing on. + + Non-bug suggestions are always welcome as well. If you have +questions about things that are unclear in the documentation or are +just obscure features, please report them too. + + +File: m4.info, Node: Manual, Prev: Bugs, Up: Preliminaries + +1.4 Using this manual +===================== + +This manual contains a number of examples of `m4' input and output, and +a simple notation is used to distinguish input, output and error +messages from `m4'. Examples are set out from the normal text, and +shown in a fixed width font, like this + + This is an example of an example! + + To distinguish input from output, all output from `m4' is prefixed +by the string `=>', and all error messages by the string `error-->'. +When showing how command line options affect matters, the command line +is shown with a prompt `$ like this', otherwise, you can assume that a +simple `m4' invocation will work. Thus: + + $ command line to invoke m4 + Example of input line + =>Output line from m4 + error-->and an error message + + The sequence `^D' in an example indicates the end of the input file. +The sequence `<NL>' refers to the newline character. The majority of +these examples are self-contained, and you can run them with similar +results by invoking `m4 -d'. In fact, the testsuite that is bundled in +the GNU M4 package consists of the examples in this document! Some of +the examples assume that your current directory is located where you +unpacked the installation, so if you plan on following along, you may +find it helpful to do this now: + + $ cd m4-1.4.16 + + As each of the predefined macros in `m4' is described, a prototype +call of the macro will be shown, giving descriptive names to the +arguments, e.g., + + -- Composite: example (STRING, [COUNT = `1'], [ARGUMENT]...) + This is a sample prototype. There is not really a macro named + `example', but this documents that if there were, it would be a + Composite macro, rather than a Builtin. It requires at least one + argument, STRING. Remember that in `m4', there must not be a + space between the macro name and the opening parenthesis, unless + it was intended to call the macro without any arguments. The + brackets around COUNT and ARGUMENT show that these arguments are + optional. If COUNT is omitted, the macro behaves as if count were + `1', whereas if ARGUMENT is omitted, the macro behaves as if it + were the empty string. A blank argument is not the same as an + omitted argument. For example, `example(`a')', `example(`a',`1')', + and `example(`a',`1',)' would behave identically with COUNT set to + `1'; while `example(`a',)' and `example(`a',`')' would explicitly + pass the empty string for COUNT. The ellipses (`...') show that + the macro processes additional arguments after ARGUMENT, rather + than ignoring them. + + All macro arguments in `m4' are strings, but some are given special +interpretation, e.g., as numbers, file names, regular expressions, etc. +The documentation for each macro will state how the parameters are +interpreted, and what happens if the argument cannot be parsed +according to the desired interpretation. Unless specified otherwise, a +parameter specified to be a number is parsed as a decimal, even if the +argument has leading zeros; and parsing the empty string as a number +results in 0 rather than an error, although a warning will be issued. + + This document consistently writes and uses "builtin", without a +hyphen, as if it were an English word. This is how the `builtin' +primitive is spelled within `m4'. + + +File: m4.info, Node: Invoking m4, Next: Syntax, Prev: Preliminaries, Up: Top + +2 Invoking `m4' +*************** + +The format of the `m4' command is: + + `m4' [OPTION...] [FILE...] + + All options begin with `-', or if long option names are used, with +`--'. A long option name need not be written completely, any +unambiguous prefix is sufficient. POSIX requires `m4' to recognize +arguments intermixed with files, even when `POSIXLY_CORRECT' is set in +the environment. Most options take effect at startup regardless of +their position, but some are documented below as taking effect after +any files that occurred earlier in the command line. The argument `--' +is a marker to denote the end of options. + + With short options, options that do not take arguments may be +combined into a single command line argument with subsequent options, +options with mandatory arguments may be provided either as a single +command line argument or as two arguments, and options with optional +arguments must be provided as a single argument. In other words, `m4 +-QPDfoo -d a -df' is equivalent to `m4 -Q -P -D foo -d -df -- ./a', +although the latter form is considered canonical. + + With long options, options with mandatory arguments may be provided +with an equal sign (`=') in a single argument, or as two arguments, and +options with optional arguments must be provided as a single argument. +In other words, `m4 --def foo --debug a' is equivalent to `m4 +--define=foo --debug= -- ./a', although the latter form is considered +canonical (not to mention more robust, in case a future version of `m4' +introduces an option named `--default'). + + `m4' understands the following options, grouped by functionality. + +* Menu: + +* Operation modes:: Command line options for operation modes +* Preprocessor features:: Command line options for preprocessor features +* Limits control:: Command line options for limits control +* Frozen state:: Command line options for frozen state +* Debugging options:: Command line options for debugging +* Command line files:: Specifying input files on the command line + + +File: m4.info, Node: Operation modes, Next: Preprocessor features, Up: Invoking m4 + +2.1 Command line options for operation modes +============================================ + +Several options control the overall operation of `m4': + +`--help' + Print a help summary on standard output, then immediately exit + `m4' without reading any input files or performing any other + actions. + +`--version' + Print the version number of the program on standard output, then + immediately exit `m4' without reading any input files or + performing any other actions. + +`-E' +`--fatal-warnings' + Controls the effect of warnings. If unspecified, then execution + continues and exit status is unaffected when a warning is printed. + If specified exactly once, warnings become fatal; when one is + issued, execution continues, but the exit status will be non-zero. + If specified multiple times, then execution halts with non-zero + status the first time a warning is issued. The introduction of + behavior levels is new to M4 1.4.9; for behavior consistent with + earlier versions, you should specify `-E' twice. + +`-i' +`--interactive' +`-e' + Makes this invocation of `m4' interactive. This means that all + output will be unbuffered, and interrupts will be ignored. The + spelling `-e' exists for compatibility with other `m4' + implementations, and issues a warning because it may be withdrawn + in a future version of GNU M4. + +`-P' +`--prefix-builtins' + Internally modify _all_ builtin macro names so they all start with + the prefix `m4_'. For example, using this option, one should write + `m4_define' instead of `define', and `m4___file__' instead of + `__file__'. This option has no effect if `-R' is also specified. + +`-Q' +`--quiet' +`--silent' + Suppress warnings, such as missing or superfluous arguments in + macro calls, or treating the empty string as zero. + +`--warn-macro-sequence[=REGEXP]' + Issue a warning if the regular expression REGEXP has a non-empty + match in any macro definition (either by `define' or `pushdef'). + Empty matches are ignored; therefore, supplying the empty string + as REGEXP disables any warning. If the optional REGEXP is not + supplied, then the default regular expression is + `\$\({[^}]*}\|[0-9][0-9]+\)' (a literal `$' followed by multiple + digits or by an open brace), since these sequences will change + semantics in the default operation of GNU M4 2.0 (due to a change + in how more than 9 arguments in a macro definition will be + handled, *note Arguments::). Providing an alternate regular + expression can provide a useful reverse lookup feature of finding + where a macro is defined to have a given definition. + +`-W REGEXP' +`--word-regexp=REGEXP' + Use REGEXP as an alternative syntax for macro names. This + experimental option will not be present in all GNU `m4' + implementations (*note Changeword::). + + +File: m4.info, Node: Preprocessor features, Next: Limits control, Prev: Operation modes, Up: Invoking m4 + +2.2 Command line options for preprocessor features +================================================== + +Several options allow `m4' to behave more like a preprocessor. Macro +definitions and deletions can be made on the command line, the search +path can be altered, and the output file can track where the input came +from. These features occur with the following options: + +`-D NAME[=VALUE]' +`--define=NAME[=VALUE]' + This enters NAME into the symbol table. If `=VALUE' is missing, + the value is taken to be the empty string. The VALUE can be any + string, and the macro can be defined to take arguments, just as if + it was defined from within the input. This option may be given + more than once; order with respect to file names is significant, + and redefining the same NAME loses the previous value. + +`-I DIRECTORY' +`--include=DIRECTORY' + Make `m4' search DIRECTORY for included files that are not found + in the current working directory. *Note Search Path::, for more + details. This option may be given more than once. + +`-s' +`--synclines' + Generate synchronization lines, for use by the C preprocessor or + other similar tools. Order is significant with respect to file + names. This option is useful, for example, when `m4' is used as a + front end to a compiler. Source file name and line number + information is conveyed by directives of the form `#line LINENUM + "FILE"', which are inserted as needed into the middle of the + output. Such directives mean that the following line originated + or was expanded from the contents of input file FILE at line + LINENUM. The `"FILE"' part is often omitted when the file name + did not change from the previous directive. + + Synchronization directives are always given on complete lines by + themselves. When a synchronization discrepancy occurs in the + middle of an output line, the associated synchronization directive + is delayed until the next newline that does not occur in the + middle of a quoted string or comment. + + define(`twoline', `1 + 2') + =>#line 2 "stdin" + => + changecom(`/*', `*/') + => + define(`comment', `/*1 + 2*/') + =>#line 5 + => + dnl no line + hello + =>#line 7 + =>hello + twoline + =>1 + =>#line 8 + =>2 + comment + =>/*1 + =>2*/ + one comment `two + three' + =>#line 10 + =>one /*1 + =>2*/ two + =>three + goodbye + =>#line 12 + =>goodbye + +`-U NAME' +`--undefine=NAME' + This deletes any predefined meaning NAME might have. Obviously, + only predefined macros can be deleted in this way. This option + may be given more than once; undefining a NAME that does not have a + definition is silently ignored. Order is significant with respect + to file names. + + +File: m4.info, Node: Limits control, Next: Frozen state, Prev: Preprocessor features, Up: Invoking m4 + +2.3 Command line options for limits control +=========================================== + +There are some limits within `m4' that can be tuned. For +compatibility, `m4' also accepts some options that control limits in +other implementations, but which are automatically unbounded (limited +only by your hardware and operating system constraints) in GNU `m4'. + +`-g' +`--gnu' + Enable all the extensions in this implementation. In this release + of M4, this option is always on by default; it is currently only + useful when overriding a prior use of `--traditional'. However, + having GNU behavior as default makes it impossible to write a + strictly POSIX-compliant client that avoids all incompatible GNU + M4 extensions, since such a client would have to use the non-POSIX + command-line option to force full POSIX behavior. Thus, a future + version of M4 will be changed to implicitly use the option + `--traditional' if the environment variable `POSIXLY_CORRECT' is + set. Projects that intentionally use GNU extensions should + consider using `--gnu' to state their intentions, so that the + project will not mysteriously break if the user upgrades to a + newer M4 and has `POSIXLY_CORRECT' set in their environment. + +`-G' +`--traditional' + Suppress all the extensions made in this implementation, compared + to the System V version. *Note Compatibility::, for a list of + these. + +`-H NUM' +`--hashsize=NUM' + Make the internal hash table for symbol lookup be NUM entries big. + For better performance, the number should be prime, but this is not + checked. The default is 509 entries. It should not be necessary + to increase this value, unless you define an excessive number of + macros. + +`-L NUM' +`--nesting-limit=NUM' + Artificially limit the nesting of macro calls to NUM levels, + stopping program execution if this limit is ever exceeded. When + not specified, nesting defaults to unlimited on platforms that can + detect stack overflow, and to 1024 levels otherwise. A value of + zero means unlimited; but then heavily nested code could + potentially cause a stack overflow. + + The precise effect of this option is more correctly associated + with textual nesting than dynamic recursion. It has been useful + when some complex `m4' input was generated by mechanical means, and + also in diagnosing recursive algorithms that do not scale well. + Most users never need to change this option from its default. + + This option does _not_ have the ability to break endless + rescanning loops, since these do not necessarily consume much + memory or stack space. Through clever usage of rescanning loops, + one can request complex, time-consuming computations from `m4' + with useful results. Putting limitations in this area would break + `m4' power. There are many pathological cases: + `define(`a', `a')a' is only the simplest example (but *note + Compatibility::). Expecting GNU `m4' to detect these would be a + little like expecting a compiler system to detect and diagnose + endless loops: it is a quite _hard_ problem in general, if not + undecidable! + +`-B NUM' +`-S NUM' +`-T NUM' + These options are present for compatibility with System V `m4', but + do nothing in this implementation. They may disappear in future + releases, and issue a warning to that effect. + +`-N NUM' +`--diversions=NUM' + These options are present only for compatibility with previous + versions of GNU `m4', and were controlling the number of possible + diversions which could be used at the same time. They do nothing, + because there is no fixed limit anymore. They may disappear in + future releases, and issue a warning to that effect. + + +File: m4.info, Node: Frozen state, Next: Debugging options, Prev: Limits control, Up: Invoking m4 + +2.4 Command line options for frozen state +========================================= + +GNU `m4' comes with a feature of freezing internal state (*note Frozen +files::). This can be used to speed up `m4' execution when reusing a +common initialization script. + +`-F FILE' +`--freeze-state=FILE' + Once execution is finished, write out the frozen state on the + specified FILE. It is conventional, but not required, for FILE to + end in `.m4f'. + +`-R FILE' +`--reload-state=FILE' + Before execution starts, recover the internal state from the + specified frozen FILE. The options `-D', `-U', and `-t' take + effect after state is reloaded, but before the input files are + read. + + +File: m4.info, Node: Debugging options, Next: Command line files, Prev: Frozen state, Up: Invoking m4 + +2.5 Command line options for debugging +====================================== + +Finally, there are several options for aiding in debugging `m4' scripts. + +`-d[FLAGS]' +`--debug[=FLAGS]' + Set the debug-level according to the flags FLAGS. The debug-level + controls the format and amount of information presented by the + debugging functions. *Note Debug Levels::, for more details on + the format and meaning of FLAGS. If omitted, FLAGS defaults to + `aeq'. + +`--debugfile[=FILE]' +`-o FILE' +`--error-output=FILE' + Redirect `dumpdef' output, debug messages, and trace output to the + named FILE. Warnings, error messages, and `errprint' output are + still printed to standard error. If these options are not used, or + if FILE is unspecified (only possible for `--debugfile'), debug + output goes to standard error; if FILE is the empty string, debug + output is discarded. *Note Debug Output::, for more details. The + option `--debugfile' may be given more than once, and order is + significant with respect to file names. The spellings `-o' and + `--error-output' are misleading and inconsistent with other GNU + tools; for now they are silently accepted as synonyms of + `--debugfile' and only recognized once, but in a future version of + M4, using them will cause a warning to be issued. + +`-l NUM' +`--arglength=NUM' + Restrict the size of the output generated by macro tracing to NUM + characters per trace line. If unspecified or zero, output is + unlimited. *Note Debug Levels::, for more details. + +`-t NAME' +`--trace=NAME' + This enables tracing for the macro NAME, at any point where it is + defined. NAME need not be defined when this option is given. + This option may be given more than once, and order is significant + with respect to file names. *Note Trace::, for more details. + + +File: m4.info, Node: Command line files, Prev: Debugging options, Up: Invoking m4 + +2.6 Specifying input files on the command line +============================================== + +The remaining arguments on the command line are taken to be input file +names. If no names are present, standard input is read. A file name +of `-' is taken to mean standard input. It is conventional, but not +required, for input files to end in `.m4'. + + The input files are read in the sequence given. Standard input can +be read more than once, so the file name `-' may appear multiple times +on the command line; this makes a difference when input is from a +terminal or other special file type. It is an error if an input file +ends in the middle of argument collection, a comment, or a quoted +string. + + The options `--define' (`-D'), `--undefine' (`-U'), `--synclines' +(`-s'), and `--trace' (`-t') only take effect after processing input +from any file names that occur earlier on the command line. For +example, assume the file `foo' contains: + + $ cat foo + bar + + The text `bar' can then be redefined over multiple uses of `foo': + + $ m4 -Dbar=hello foo -Dbar=world foo + =>hello + =>world + + If none of the input files invoked `m4exit' (*note M4exit::), the +exit status of `m4' will be 0 for success, 1 for general failure (such +as problems with reading an input file), and 63 for version mismatch +(*note Using frozen files::). + + If you need to read a file whose name starts with a `-', you can +specify it as `./-file', or use `--' to mark the end of options. + + +File: m4.info, Node: Syntax, Next: Macros, Prev: Invoking m4, Up: Top + +3 Lexical and syntactic conventions +*********************************** + +As `m4' reads its input, it separates it into "tokens". A token is +either a name, a quoted string, or any single character, that is not a +part of either a name or a string. Input to `m4' can also contain +comments. GNU `m4' does not yet understand multibyte locales; all +operations are byte-oriented rather than character-oriented (although +if your locale uses a single byte encoding, such as ISO-8859-1, you +will not notice a difference). However, `m4' is eight-bit clean, so +you can use non-ASCII characters in quoted strings (*note +Changequote::), comments (*note Changecom::), and macro names (*note +Indir::), with the exception of the NUL character (the zero byte +`'\0''). + +* Menu: + +* Names:: Macro names +* Quoted strings:: Quoting input to `m4' +* Comments:: Comments in `m4' input +* Other tokens:: Other kinds of input tokens +* Input processing:: How `m4' copies input to output + + +File: m4.info, Node: Names, Next: Quoted strings, Up: Syntax + +3.1 Macro names +=============== + +A name is any sequence of letters, digits, and the character `_' +(underscore), where the first character is not a digit. `m4' will use +the longest such sequence found in the input. If a name has a macro +definition, it will be subject to macro expansion (*note Macros::). +Names are case-sensitive. + + Examples of legal names are: `foo', `_tmp', and `name01'. + + +File: m4.info, Node: Quoted strings, Next: Comments, Prev: Names, Up: Syntax + +3.2 Quoting input to `m4' +========================= + +A quoted string is a sequence of characters surrounded by quote +strings, defaulting to ``' and `'', where the nested begin and end +quotes within the string are balanced. The value of a string token is +the text, with one level of quotes stripped off. Thus + + `' + => + +is the empty string, and double-quoting turns into single-quoting. + + ``quoted'' + =>`quoted' + + The quote characters can be changed at any time, using the builtin +macro `changequote'. *Note Changequote::, for more information. + + +File: m4.info, Node: Comments, Next: Other tokens, Prev: Quoted strings, Up: Syntax + +3.3 Comments in `m4' input +========================== + +Comments in `m4' are normally delimited by the characters `#' and +newline. All characters between the comment delimiters are ignored, +but the entire comment (including the delimiters) is passed through to +the output--comments are _not_ discarded by `m4'. + + Comments cannot be nested, so the first newline after a `#' ends the +comment. The commenting effect of the begin-comment string can be +inhibited by quoting it. + + $ m4 + `quoted text' # `commented text' + =>quoted text # `commented text' + `quoting inhibits' `#' `comments' + =>quoting inhibits # comments + + The comment delimiters can be changed to any string at any time, +using the builtin macro `changecom'. *Note Changecom::, for more +information. + + +File: m4.info, Node: Other tokens, Next: Input processing, Prev: Comments, Up: Syntax + +3.4 Other kinds of input tokens +=============================== + +Any character, that is neither a part of a name, nor of a quoted string, +nor a comment, is a token by itself. When not in the context of macro +expansion, all of these tokens are just copied to output. However, +during macro expansion, whitespace characters (space, tab, newline, +formfeed, carriage return, vertical tab), parentheses (`(' and `)'), +comma (`,'), and dollar (`$') have additional roles, explained later. + + +File: m4.info, Node: Input processing, Prev: Other tokens, Up: Syntax + +3.5 How `m4' copies input to output +=================================== + +As `m4' reads the input token by token, it will copy each token +directly to the output immediately. + + The exception is when it finds a word with a macro definition. In +that case `m4' will calculate the macro's expansion, possibly reading +more input to get the arguments. It then inserts the expansion in front +of the remaining input. In other words, the resulting text from a macro +call will be read and parsed into tokens again. + + `m4' expands a macro as soon as possible. If it finds a macro call +when collecting the arguments to another, it will expand the second call +first. This process continues until there are no more macro calls to +expand and all the input has been consumed. + + For a running example, examine how `m4' handles this input: + + format(`Result is %d', eval(`2**15')) + +First, `m4' sees that the token `format' is a macro name, so it +collects the tokens `(', ``Result is %d'', `,', and ` ', before +encountering another potential macro. Sure enough, `eval' is a macro +name, so the nested argument collection picks up `(', ``2**15'', and +`)', invoking the eval macro with the lone argument of `2**15'. The +expansion of `eval(2**15)' is `32768', which is then rescanned as the +five tokens `3', `2', `7', `6', and `8'; and combined with the next +`)', the format macro now has all its arguments, as if the user had +typed: + + format(`Result is %d', 32768) + +The format macro expands to `Result is 32768', and we have another +round of scanning for the tokens `Result', ` ', `is', ` ', `3', `2', +`7', `6', and `8'. None of these are macros, so the final output is + + =>Result is 32768 + + As a more complicated example, we will contrast an actual code +example from the Gnulib project(1), showing both a buggy approach and +the desired results. The user desires to output a shell assignment +statement that takes its argument and turns it into a shell variable by +converting it to uppercase and prepending a prefix. The original +attempt looks like this: + + changequote([,])dnl + define([gl_STRING_MODULE_INDICATOR], + [ + dnl comment + GNULIB_]translit([$1],[a-z],[A-Z])[=1 + ])dnl + gl_STRING_MODULE_INDICATOR([strcase]) + => + => GNULIB_strcase=1 + => + + Oops - the argument did not get capitalized. And although the manual +is not able to easily show it, both lines that appear empty actually +contain two trailing spaces. By stepping through the parse, it is easy +to see what happened. First, `m4' sees the token `changequote', which +it recognizes as a macro, followed by `(', `[', `,', `]', and `)' to +form the argument list. The macro expands to the empty string, but +changes the quoting characters to something more useful for generating +shell code (unbalanced ``' and `'' appear all the time in shell scripts, +but unbalanced `[]' tend to be rare). Also in the first line, `m4' +sees the token `dnl', which it recognizes as a builtin macro that +consumes the rest of the line, resulting in no output for that line. + + The second line starts a macro definition. `m4' sees the token +`define', which it recognizes as a macro, followed by a `(', +`[gl_STRING_MODULE_INDICATOR]', and `,'. Because an unquoted comma was +encountered, the first argument is known to be the expansion of the +single-quoted string token, or `gl_STRING_MODULE_INDICATOR'. Next, +`m4' sees `<NL>', ` ', and ` ', but this whitespace is discarded as +part of argument collection. Then comes a rather lengthy single-quoted +string token, `[<NL> dnl comment<NL> GNULIB_]'. This is followed +by the token `translit', which `m4' recognizes as a macro name, so a +nested macro expansion has started. + + The arguments to the `translit' are found by the tokens `(', `[$1]', +`,', `[a-z]', `,', `[A-Z]', and finally `)'. All three string +arguments are expanded (or in other words, the quotes are stripped), +and since neither `$' nor `1' need capitalization, the result of the +macro is `$1'. This expansion is rescanned, resulting in the two +literal characters `$' and `1'. + + Scanning of the outer macro resumes, and picks up with `[=1<NL> ]', +and finally `)'. The collected pieces of expanded text are +concatenated, with the end result that the macro +`gl_STRING_MODULE_INDICATOR' is now defined to be the sequence `<NL> +dnl comment<NL> GNULIB_$1=1<NL> '. Once again, `dnl' is recognized +and avoids a newline in the output. + + The final line is then parsed, beginning with ` ' and ` ' that are +output literally. Then `gl_STRING_MODULE_INDICATOR' is recognized as a +macro name, with an argument list of `(', `[strcase]', and `)'. Since +the definition of the macro contains the sequence `$1', that sequence +is replaced with the argument `strcase' prior to starting the rescan. +The rescan sees `<NL>' and four spaces, which are output literally, then +`dnl', which discards the text ` comment<NL>'. Next comes four more +spaces, also output literally, and the token `GNULIB_strcase', which +resulted from the earlier parameter substitution. Since that is not a +macro name, it is output literally, followed by the literal tokens `=', +`1', `<NL>', and two more spaces. Finally, the original `<NL>' seen +after the macro invocation is scanned and output literally. + + Now for a corrected approach. This rearranges the use of newlines +and whitespace so that less whitespace is output (which, although +harmless to shell scripts, can be visually unappealing), and fixes the +quoting issues so that the capitalization occurs when the macro +`gl_STRING_MODULE_INDICATOR' is invoked, rather then when it is +defined. It also adds another layer of quoting to the first argument of +`translit', to ensure that the output will be rescanned as a string +rather than a potential uppercase macro name needing further expansion. + + changequote([,])dnl + define([gl_STRING_MODULE_INDICATOR], + [dnl comment + GNULIB_[]translit([[$1]], [a-z], [A-Z])=1dnl + ])dnl + gl_STRING_MODULE_INDICATOR([strcase]) + => GNULIB_STRCASE=1 + + The parsing of the first line is unchanged. The second line sees the +name of the macro to define, then sees the discarded `<NL>' and two +spaces, as before. But this time, the next token is `[dnl comment<NL> +GNULIB_[]translit([[$1]], [a-z], [A-Z])=1dnl<NL>]', which includes +nested quotes, followed by `)' to end the macro definition and `dnl' to +skip the newline. No early expansion of `translit' occurs, so the +entire string becomes the definition of the macro. + + The final line is then parsed, beginning with two spaces that are +output literally, and an invocation of `gl_STRING_MODULE_INDICATOR' +with the argument `strcase'. Again, the `$1' in the macro definition +is substituted prior to rescanning. Rescanning first encounters `dnl', +and discards ` comment<NL>'. Then two spaces are output literally. +Next comes the token `GNULIB_', but that is not a macro, so it is +output literally. The token `[]' is an empty string, so it does not +affect output. Then the token `translit' is encountered. + + This time, the arguments to `translit' are parsed as `(', +`[[strcase]]', `,', ` ', `[a-z]', `,', ` ', `[A-Z]', and `)'. The two +spaces are discarded, and the translit results in the desired result +`[STRCASE]'. This is rescanned, but since it is a string, the quotes +are stripped and the only output is a literal `STRCASE'. Then the +scanner sees `=' and `1', which are output literally, followed by `dnl' +which discards the rest of the definition of +`gl_STRING_MODULE_INDICATOR'. The newline at the end of output is the +literal `<NL>' that appeared after the invocation of the macro. + + The order in which `m4' expands the macros can be further explored +using the trace facilities of GNU `m4' (*note Trace::). + + ---------- Footnotes ---------- + + (1) Derived from a patch in +`http://lists.gnu.org/archive/html/bug-gnulib/2007-01/msg00389.html', +and a followup patch in +`http://lists.gnu.org/archive/html/bug-gnulib/2007-02/msg00000.html' + + +File: m4.info, Node: Macros, Next: Definitions, Prev: Syntax, Up: Top + +4 How to invoke macros +********************** + +This chapter covers macro invocation, macro arguments and how macro +expansion is treated. + +* Menu: + +* Invocation:: Macro invocation +* Inhibiting Invocation:: Preventing macro invocation +* Macro Arguments:: Macro arguments +* Quoting Arguments:: On Quoting Arguments to macros +* Macro expansion:: Expanding macros + + +File: m4.info, Node: Invocation, Next: Inhibiting Invocation, Up: Macros + +4.1 Macro invocation +==================== + +Macro invocations has one of the forms + + name + +which is a macro invocation without any arguments, or + + name(arg1, arg2, ..., argN) + +which is a macro invocation with N arguments. Macros can have any +number of arguments. All arguments are strings, but different macros +might interpret the arguments in different ways. + + The opening parenthesis _must_ follow the NAME directly, with no +spaces in between. If it does not, the macro is called with no +arguments at all. + + For a macro call to have no arguments, the parentheses _must_ be +left out. The macro call + + name() + +is a macro call with one argument, which is the empty string, not a call +with no arguments. + + +File: m4.info, Node: Inhibiting Invocation, Next: Macro Arguments, Prev: Invocation, Up: Macros + +4.2 Preventing macro invocation +=============================== + +An innovation of the `m4' language, compared to some of its +predecessors (like Strachey's `GPM', for example), is the ability to +recognize macro calls without resorting to any special, prefixed +invocation character. While generally useful, this feature might +sometimes be the source of spurious, unwanted macro calls. So, GNU +`m4' offers several mechanisms or techniques for inhibiting the +recognition of names as macro calls. + + First of all, many builtin macros cannot meaningfully be called +without arguments. As a GNU extension, for any of these macros, +whenever an opening parenthesis does not immediately follow their name, +the builtin macro call is not triggered. This solves the most usual +cases, like for `include' or `eval'. Later in this document, the +sentence "This macro is recognized only with parameters" refers to this +specific provision of GNU M4, also known as a blind builtin macro. For +the builtins defined by POSIX that bear this disclaimer, POSIX +specifically states that invoking those builtins without arguments is +unspecified, because many other implementations simply invoke the +builtin as though it were given one empty argument instead. + + $ m4 + eval + =>eval + eval(`1') + =>1 + + There is also a command line option (`--prefix-builtins', or `-P', +*note Invoking m4: Operation modes.) that renames all builtin macros +with a prefix of `m4_' at startup. The option has no effect whatsoever +on user defined macros. For example, with this option, one has to +write `m4_dnl' and even `m4_m4exit'. It also has no effect on whether +a macro requires parameters. + + $ m4 -P + eval + =>eval + eval(`1') + =>eval(1) + m4_eval + =>m4_eval + m4_eval(`1') + =>1 + + Another alternative is to redefine problematic macros to a name less +likely to cause conflicts, *Note Definitions::. + + If your version of GNU `m4' has the `changeword' feature compiled +in, it offers far more flexibility in specifying the syntax of macro +names, both builtin or user-defined. *Note Changeword::, for more +information on this experimental feature. + + Of course, the simplest way to prevent a name from being interpreted +as a call to an existing macro is to quote it. The remainder of this +section studies a little more deeply how quoting affects macro +invocation, and how quoting can be used to inhibit macro invocation. + + Even if quoting is usually done over the whole macro name, it can +also be done over only a few characters of this name (provided, of +course, that the unquoted portions are not also a macro). It is also +possible to quote the empty string, but this works only _inside_ the +name. For example: + + `divert' + =>divert + `d'ivert + =>divert + di`ver't + =>divert + div`'ert + =>divert + +all yield the string `divert'. While in both: + + `'divert + => + divert`' + => + +the `divert' builtin macro will be called, which expands to the empty +string. + + The output of macro evaluations is always rescanned. In the +following example, the input `x`'y' yields the string `bCD', exactly as +if `m4' has been given `substr(ab`'cde, `1', `3')' as input: + + define(`cde', `CDE') + => + define(`x', `substr(ab') + => + define(`y', `cde, `1', `3')') + => + x`'y + =>bCD + + Unquoted strings on either side of a quoted string are subject to +being recognized as macro names. In the following example, quoting the +empty string allows for the second `macro' to be recognized as such: + + define(`macro', `m') + => + macro(`m')macro + =>mmacro + macro(`m')`'macro + =>mm + + Quoting may prevent recognizing as a macro name the concatenation of +a macro expansion with the surrounding characters. In this example: + + define(`macro', `di$1') + => + macro(`v')`ert' + =>divert + macro(`v')ert + => + +the input will produce the string `divert'. When the quotes were +removed, the `divert' builtin was called instead. + + +File: m4.info, Node: Macro Arguments, Next: Quoting Arguments, Prev: Inhibiting Invocation, Up: Macros + +4.3 Macro arguments +=================== + +When a name is seen, and it has a macro definition, it will be expanded +as a macro. + + If the name is followed by an opening parenthesis, the arguments +will be collected before the macro is called. If too few arguments are +supplied, the missing arguments are taken to be the empty string. +However, some builtins are documented to behave differently for a +missing optional argument than for an explicit empty string. If there +are too many arguments, the excess arguments are ignored. Unquoted +leading whitespace is stripped off all arguments, but whitespace +generated by a macro expansion or occurring after a macro that expanded +to an empty string remains intact. Whitespace includes space, tab, +newline, carriage return, vertical tab, and formfeed. + + define(`macro', `$1') + => + macro( unquoted leading space lost) + =>unquoted leading space lost + macro(` quoted leading space kept') + => quoted leading space kept + macro( + divert `unquoted space kept after expansion') + => unquoted space kept after expansion + macro(macro(` + ')`whitespace from expansion kept') + => + =>whitespace from expansion kept + macro(`unquoted trailing whitespace kept' + ) + =>unquoted trailing whitespace kept + => + + Normally `m4' will issue warnings if a builtin macro is called with +an inappropriate number of arguments, but it can be suppressed with the +`--quiet' command line option (or `--silent', or `-Q', *note Invoking +m4: Operation modes.). For user defined macros, there is no check of +the number of arguments given. + + $ m4 + index(`abc') + error-->m4:stdin:1: Warning: too few arguments to builtin `index' + =>0 + index(`abc',) + =>0 + index(`abc', `b', `ignored') + error-->m4:stdin:3: Warning: excess arguments to builtin `index' ignored + =>1 + + $ m4 -Q + index(`abc') + =>0 + index(`abc',) + =>0 + index(`abc', `b', `ignored') + =>1 + + Macros are expanded normally during argument collection, and whatever +commas, quotes and parentheses that might show up in the resulting +expanded text will serve to define the arguments as well. Thus, if FOO +expands to `, b, c', the macro call + + bar(a foo, d) + +is a macro call with four arguments, which are `a ', `b', `c' and `d'. +To understand why the first argument contains whitespace, remember that +unquoted leading whitespace is never part of an argument, but trailing +whitespace always is. + + It is possible for a macro's definition to change during argument +collection, in which case the expansion uses the definition that was in +effect at the time the opening `(' was seen. + + define(`f', `1') + => + f(define(`f', `2')) + =>1 + f + =>2 + + It is an error if the end of file occurs while collecting arguments. + + hello world + =>hello world + define( + ^D + error-->m4:stdin:2: ERROR: end of file in argument list + + +File: m4.info, Node: Quoting Arguments, Next: Macro expansion, Prev: Macro Arguments, Up: Macros + +4.4 On Quoting Arguments to macros +================================== + +Each argument has unquoted leading whitespace removed. Within each +argument, all unquoted parentheses must match. For example, if FOO is +a macro, + + foo(() (`(') `(') + +is a macro call, with one argument, whose value is `() (() ('. Commas +separate arguments, except when they occur inside quotes, comments, or +unquoted parentheses. *Note Pseudo Arguments::, for examples. + + It is common practice to quote all arguments to macros, unless you +are sure you want the arguments expanded. Thus, in the above example +with the parentheses, the `right' way to do it is like this: + + foo(`() (() (') + + It is, however, in certain cases necessary (because nested expansion +must occur to create the arguments for the outer macro) or convenient +(because it uses fewer characters) to leave out quotes for some +arguments, and there is nothing wrong in doing it. It just makes life a +bit harder, if you are not careful to follow a consistent quoting style. +For consistency, this manual follows the rule of thumb that each layer +of parentheses introduces another layer of single quoting, except when +showing the consequences of quoting rules. This is done even when the +quoted string cannot be a macro, such as with integers when you have not +changed the syntax via `changeword' (*note Changeword::). + + The quoting rule of thumb of one level of quoting per parentheses +has a nice property: when a macro name appears inside parentheses, you +can determine when it will be expanded. If it is not quoted, it will be +expanded prior to the outer macro, so that its expansion becomes the +argument. If it is single-quoted, it will be expanded after the outer +macro. And if it is double-quoted, it will be used as literal text +instead of a macro name. + + define(`active', `ACT, IVE') + => + define(`show', `$1 $1') + => + show(active) + =>ACT ACT + show(`active') + =>ACT, IVE ACT, IVE + show(``active'') + =>active active + + +File: m4.info, Node: Macro expansion, Prev: Quoting Arguments, Up: Macros + +4.5 Macro expansion +=================== + +When the arguments, if any, to a macro call have been collected, the +macro is expanded, and the expansion text is pushed back onto the input +(unquoted), and reread. The expansion text from one macro call might +therefore result in more macros being called, if the calls are included, +completely or partially, in the first macro calls' expansion. + + Taking a very simple example, if FOO expands to `bar', and BAR +expands to `Hello', the input + + $ m4 -Dbar=Hello -Dfoo=bar + foo + =>Hello + +will expand first to `bar', and when this is reread and expanded, into +`Hello'. + + +File: m4.info, Node: Definitions, Next: Conditionals, Prev: Macros, Up: Top + +5 How to define new macros +************************** + +Macros can be defined, redefined and deleted in several different ways. +Also, it is possible to redefine a macro without losing a previous +value, and bring back the original value at a later time. + +* Menu: + +* Define:: Defining a new macro +* Arguments:: Arguments to macros +* Pseudo Arguments:: Special arguments to macros +* Undefine:: Deleting a macro +* Defn:: Renaming macros +* Pushdef:: Temporarily redefining macros + +* Indir:: Indirect call of macros +* Builtin:: Indirect call of builtins + + +File: m4.info, Node: Define, Next: Arguments, Up: Definitions + +5.1 Defining a macro +==================== + +The normal way to define or redefine macros is to use the builtin +`define': + + -- Builtin: define (NAME, [EXPANSION]) + Defines NAME to expand to EXPANSION. If EXPANSION is not given, + it is taken to be empty. + + The expansion of `define' is void. The macro `define' is + recognized only with parameters. + + The following example defines the macro FOO to expand to the text +`Hello World.'. + + define(`foo', `Hello world.') + => + foo + =>Hello world. + + The empty line in the output is there because the newline is not a +part of the macro definition, and it is consequently copied to the +output. This can be avoided by use of the macro `dnl'. *Note Dnl::, +for details. + + The first argument to `define' should be quoted; otherwise, if the +macro is already defined, you will be defining a different macro. This +example shows the problems with underquoting, since we did not want to +redefine `one': + + define(foo, one) + => + define(foo, two) + => + one + =>two + + GNU `m4' normally replaces only the _topmost_ definition of a macro +if it has several definitions from `pushdef' (*note Pushdef::). Some +other implementations of `m4' replace all definitions of a macro with +`define'. *Note Incompatibilities::, for more details. + + As a GNU extension, the first argument to `define' does not have to +be a simple word. It can be any text string, even the empty string. A +macro with a non-standard name cannot be invoked in the normal way, as +the name is not recognized. It can only be referenced by the builtins +`indir' (*note Indir::) and `defn' (*note Defn::). + + Arrays and associative arrays can be simulated by using non-standard +macro names. + + -- Composite: array (INDEX) + -- Composite: array_set (INDEX, [VALUE]) + Provide access to entries within an array. `array' reads the entry + at location INDEX, and `array_set' assigns VALUE to location INDEX. + + define(`array', `defn(format(``array[%d]'', `$1'))') + => + define(`array_set', `define(format(``array[%d]'', `$1'), `$2')') + => + array_set(`4', `array element no. 4') + => + array_set(`17', `array element no. 17') + => + array(`4') + =>array element no. 4 + array(eval(`10 + 7')) + =>array element no. 17 + + Change the `%d' to `%s' and it is an associative array. + + +File: m4.info, Node: Arguments, Next: Pseudo Arguments, Prev: Define, Up: Definitions + +5.2 Arguments to macros +======================= + +Macros can have arguments. The Nth argument is denoted by `$n' in the +expansion text, and is replaced by the Nth actual argument, when the +macro is expanded. Replacement of arguments happens before rescanning, +regardless of how many nesting levels of quoting appear in the +expansion. Here is an example of a macro with two arguments. + + -- Composite: exch (ARG1, ARG2) + Expands to ARG2 followed by ARG1, effectively exchanging their + order. + + define(`exch', `$2, $1') + => + exch(`arg1', `arg2') + =>arg2, arg1 + + This can be used, for example, if you like the arguments to `define' +to be reversed. + + define(`exch', `$2, $1') + => + define(exch(``expansion text'', ``macro'')) + => + macro + =>expansion text + + *Note Quoting Arguments::, for an explanation of the double quotes. +(You should try and improve this example so that clients of `exch' do +not have to double quote; or *note Answers: Improved exch.). + + As a special case, the zeroth argument, `$0', is always the name of +the macro being expanded. + + define(`test', ``Macro name: $0'') + => + test + =>Macro name: test + + If you want quoted text to appear as part of the expansion text, +remember that quotes can be nested in quoted strings. Thus, in + + define(`foo', `This is macro `foo'.') + => + foo + =>This is macro foo. + +The `foo' in the expansion text is _not_ expanded, since it is a quoted +string, and not a name. + + GNU `m4' allows the number following the `$' to consist of one or +more digits, allowing macros to have any number of arguments. The +extension of accepting multiple digits is incompatible with POSIX, and +is different than traditional implementations of `m4', which only +recognize one digit. Therefore, future versions of GNU M4 will phase +out this feature. To portably access beyond the ninth argument, you +can use the `argn' macro documented later (*note Shift::). + + POSIX also states that `$' followed immediately by `{' in a macro +definition is implementation-defined. This version of M4 passes the +literal characters `${' through unchanged, but M4 2.0 will implement an +optional feature similar to `sh', where `${11}' expands to the eleventh +argument, to replace the current recognition of `$11'. Meanwhile, if +you want to guarantee that you will get a literal `${' in output when +expanding a macro, even when you upgrade to M4 2.0, you can use nested +quoting to your advantage: + + define(`foo', `single quoted $`'{1} output') + => + define(`bar', ``double quoted $'`{2} output'') + => + foo(`a', `b') + =>single quoted ${1} output + bar(`a', `b') + =>double quoted ${2} output + + To help you detect places in your M4 input files that might change in +behavior due to the changed behavior of M4 2.0, you can use the +`--warn-macro-sequence' command-line option (*note Invoking m4: +Operation modes.) with the default regular expression. This will add a +warning any time a macro definition includes `$' followed by multiple +digits, or by `{'. The warning is not enabled by default, because it +triggers a number of warnings in Autoconf 2.61 (and Autoconf uses `-E' +to treat warnings as errors), and because it will still be possible to +restore older behavior in M4 2.0. + + $ m4 --warn-macro-sequence + define(`foo', `$001 ${1} $1') + error-->m4:stdin:1: Warning: definition of `foo' contains sequence `$001' + error-->m4:stdin:1: Warning: definition of `foo' contains sequence `${1}' + => + foo(`bar') + =>bar ${1} bar + + +File: m4.info, Node: Pseudo Arguments, Next: Undefine, Prev: Arguments, Up: Definitions + +5.3 Special arguments to macros +=============================== + +There is a special notation for the number of actual arguments supplied, +and for all the actual arguments. + + The number of actual arguments in a macro call is denoted by `$#' in +the expansion text. + + -- Composite: nargs (...) + Expands to a count of the number of arguments supplied. + + define(`nargs', `$#') + => + nargs + =>0 + nargs() + =>1 + nargs(`arg1', `arg2', `arg3') + =>3 + nargs(`commas can be quoted, like this') + =>1 + nargs(arg1#inside comments, commas do not separate arguments + still arg1) + =>1 + nargs((unquoted parentheses, like this, group arguments)) + =>1 + + Remember that `#' defaults to the comment character; if you forget +quotes to inhibit the comment behavior, your macro definition may not +end where you expected. + + dnl Attempt to define a macro to just `$#' + define(underquoted, $#) + oops) + => + underquoted + =>0) + =>oops + + The notation `$*' can be used in the expansion text to denote all +the actual arguments, unquoted, with commas in between. For example + + define(`echo', `$*') + => + echo(arg1, arg2, arg3 , arg4) + =>arg1,arg2,arg3 ,arg4 + + Often each argument should be quoted, and the notation `$@' handles +that. It is just like `$*', except that it quotes each argument. A +simple example of that is: + + define(`echo', `$@') + => + echo(arg1, arg2, arg3 , arg4) + =>arg1,arg2,arg3 ,arg4 + + Where did the quotes go? Of course, they were eaten, when the +expanded text were reread by `m4'. To show the difference, try + + define(`echo1', `$*') + => + define(`echo2', `$@') + => + define(`foo', `This is macro `foo'.') + => + echo1(foo) + =>This is macro This is macro foo.. + echo1(`foo') + =>This is macro foo. + echo2(foo) + =>This is macro foo. + echo2(`foo') + =>foo + +*Note Trace::, if you do not understand this. As another example of the +difference, remember that comments encountered in arguments are passed +untouched to the macro, and that quoting disables comments. + + define(`echo1', `$*') + => + define(`echo2', `$@') + => + define(`foo', `bar') + => + echo1(#foo'foo + foo) + =>#foo'foo + =>bar + echo2(#foo'foo + foo) + =>#foobar + =>bar' + + A `$' sign in the expansion text, that is not followed by anything +`m4' understands, is simply copied to the macro expansion, as any other +text is. + + define(`foo', `$$$ hello $$$') + => + foo + =>$$$ hello $$$ + + If you want a macro to expand to something like `$12', the judicious +use of nested quoting can put a safe character between the `$' and the +next character, relying on the rescanning to remove the nested quote. +This will prevent `m4' from interpreting the `$' sign as a reference to +an argument. + + define(`foo', `no nested quote: $1') + => + foo(`arg') + =>no nested quote: arg + define(`foo', `nested quote around $: `$'1') + => + foo(`arg') + =>nested quote around $: $1 + define(`foo', `nested empty quote after $: $`'1') + => + foo(`arg') + =>nested empty quote after $: $1 + define(`foo', `nested quote around next character: $`1'') + => + foo(`arg') + =>nested quote around next character: $1 + define(`foo', `nested quote around both: `$1'') + => + foo(`arg') + =>nested quote around both: arg + + +File: m4.info, Node: Undefine, Next: Defn, Prev: Pseudo Arguments, Up: Definitions + +5.4 Deleting a macro +==================== + +A macro definition can be removed with `undefine': + + -- Builtin: undefine (NAME...) + For each argument, remove the macro NAME. The macro names must + necessarily be quoted, since they will be expanded otherwise. + + The expansion of `undefine' is void. The macro `undefine' is + recognized only with parameters. + + foo bar blah + =>foo bar blah + define(`foo', `some')define(`bar', `other')define(`blah', `text') + => + foo bar blah + =>some other text + undefine(`foo') + => + foo bar blah + =>foo other text + undefine(`bar', `blah') + => + foo bar blah + =>foo bar blah + + Undefining a macro inside that macro's expansion is safe; the macro +still expands to the definition that was in effect at the `('. + + define(`f', ``$0':$1') + => + f(f(f(undefine(`f')`hello world'))) + =>f:f:f:hello world + f(`bye') + =>f(bye) + + It is not an error for NAME to have no macro definition. In that +case, `undefine' does nothing. + + +File: m4.info, Node: Defn, Next: Pushdef, Prev: Undefine, Up: Definitions + +5.5 Renaming macros +=================== + +It is possible to rename an already defined macro. To do this, you need +the builtin `defn': + + -- Builtin: defn (NAME...) + Expands to the _quoted definition_ of each NAME. If an argument + is not a defined macro, the expansion for that argument is empty. + + If NAME is a user-defined macro, the quoted definition is simply + the quoted expansion text. If, instead, there is only one NAME + and it is a builtin, the expansion is a special token, which + points to the builtin's internal definition. This token is only + meaningful as the second argument to `define' (and `pushdef'), and + is silently converted to an empty string in most other contexts. + Combining a builtin with anything else is not supported; a warning + is issued and the builtin is omitted from the final expansion. + + The macro `defn' is recognized only with parameters. + + Its normal use is best understood through an example, which shows +how to rename `undefine' to `zap': + + define(`zap', defn(`undefine')) + => + zap(`undefine') + => + undefine(`zap') + =>undefine(zap) + + In this way, `defn' can be used to copy macro definitions, and also +definitions of builtin macros. Even if the original macro is removed, +the other name can still be used to access the definition. + + The fact that macro definitions can be transferred also explains why +you should use `$0', rather than retyping a macro's name in its +definition: + + define(`foo', `This is `$0'') + => + define(`bar', defn(`foo')) + => + bar + =>This is bar + + Macros used as string variables should be referred through `defn', +to avoid unwanted expansion of the text: + + define(`string', `The macro dnl is very useful + ') + => + string + =>The macro + defn(`string') + =>The macro dnl is very useful + => + + However, it is important to remember that `m4' rescanning is purely +textual. If an unbalanced end-quote string occurs in a macro +definition, the rescan will see that embedded quote as the termination +of the quoted string, and the remainder of the macro's definition will +be rescanned unquoted. Thus it is a good idea to avoid unbalanced +end-quotes in macro definitions or arguments to macros. + + define(`foo', a'a) + => + define(`a', `A') + => + define(`echo', `$@') + => + foo + =>A'A + defn(`foo') + =>aA' + echo(foo) + =>AA' + + On the other hand, it is possible to exploit the fact that `defn' +can concatenate multiple macros prior to the rescanning phase, in order +to join the definitions of macros that, in isolation, have unbalanced +quotes. This is particularly useful when one has used several macros to +accumulate text that M4 should rescan as a whole. In the example below, +note how the use of `defn' on `l' in isolation opens a string, which is +not closed until the next line; but used on `l' and `r' together +results in nested quoting. + + define(`l', `<[>')define(`r', `<]>') + => + changequote(`[', `]') + => + defn([l])defn([r]) + ]) + =><[>]defn([r]) + =>) + defn([l], [r]) + =><[>][<]> + + Using `defn' to generate special tokens for builtin macros outside +of expected contexts can sometimes trigger warnings. But most of the +time, such tokens are silently converted to the empty string. + + $ m4 -d + defn(`defn') + => + define(defn(`divnum'), `cannot redefine a builtin token') + error-->m4:stdin:2: Warning: define: invalid macro name ignored + => + divnum + =>0 + len(defn(`divnum')) + =>0 + + Also note that `defn' with multiple arguments can only join text +macros, not builtins, although a future version of GNU M4 may lift this +restriction. + + $ m4 -d + define(`a', `A')define(`AA', `b') + => + traceon(`defn', `define') + => + defn(`a', `divnum', `a') + error-->m4:stdin:3: Warning: cannot concatenate builtin `divnum' + error-->m4trace: -1- defn(`a', `divnum', `a') -> ``A'`A'' + =>AA + define(`mydivnum', defn(`divnum', `divnum'))mydivnum + error-->m4:stdin:4: Warning: cannot concatenate builtin `divnum' + error-->m4:stdin:4: Warning: cannot concatenate builtin `divnum' + error-->m4trace: -2- defn(`divnum', `divnum') + error-->m4trace: -1- define(`mydivnum', `') + => + traceoff(`defn', `define') + => + + +File: m4.info, Node: Pushdef, Next: Indir, Prev: Defn, Up: Definitions + +5.6 Temporarily redefining macros +================================= + +It is possible to redefine a macro temporarily, reverting to the +previous definition at a later time. This is done with the builtins +`pushdef' and `popdef': + + -- Builtin: pushdef (NAME, [EXPANSION]) + -- Builtin: popdef (NAME...) + Analogous to `define' and `undefine'. + + These macros work in a stack-like fashion. A macro is temporarily + redefined with `pushdef', which replaces an existing definition of + NAME, while saving the previous definition, before the new one is + installed. If there is no previous definition, `pushdef' behaves + exactly like `define'. + + If a macro has several definitions (of which only one is + accessible), the topmost definition can be removed with `popdef'. + If there is no previous definition, `popdef' behaves like + `undefine'. + + The expansion of both `pushdef' and `popdef' is void. The macros + `pushdef' and `popdef' are recognized only with parameters. + + define(`foo', `Expansion one.') + => + foo + =>Expansion one. + pushdef(`foo', `Expansion two.') + => + foo + =>Expansion two. + pushdef(`foo', `Expansion three.') + => + pushdef(`foo', `Expansion four.') + => + popdef(`foo') + => + foo + =>Expansion three. + popdef(`foo', `foo') + => + foo + =>Expansion one. + popdef(`foo') + => + foo + =>foo + + If a macro with several definitions is redefined with `define', the +topmost definition is _replaced_ with the new definition. If it is +removed with `undefine', _all_ the definitions are removed, and not +only the topmost one. However, POSIX allows other implementations that +treat `define' as replacing an entire stack of definitions with a +single new definition, so to be portable to other implementations, it +may be worth explicitly using `popdef' and `pushdef' rather than +relying on the GNU behavior of `define'. + + define(`foo', `Expansion one.') + => + foo + =>Expansion one. + pushdef(`foo', `Expansion two.') + => + foo + =>Expansion two. + define(`foo', `Second expansion two.') + => + foo + =>Second expansion two. + undefine(`foo') + => + foo + =>foo + + Local variables within macros are made with `pushdef' and `popdef'. +At the start of the macro a new definition is pushed, within the macro +it is manipulated and at the end it is popped, revealing the former +definition. + + It is possible to temporarily redefine a builtin with `pushdef' and +`defn'. + + +File: m4.info, Node: Indir, Next: Builtin, Prev: Pushdef, Up: Definitions + +5.7 Indirect call of macros +=========================== + +Any macro can be called indirectly with `indir': + + -- Builtin: indir (NAME, [ARGS...]) + Results in a call to the macro NAME, which is passed the rest of + the arguments ARGS. If NAME is not defined, an error message is + printed, and the expansion is void. + + The macro `indir' is recognized only with parameters. + + This can be used to call macros with computed or "invalid" names +(`define' allows such names to be defined): + + define(`$$internal$macro', `Internal macro (name `$0')') + => + $$internal$macro + =>$$internal$macro + indir(`$$internal$macro') + =>Internal macro (name $$internal$macro) + + The point is, here, that larger macro packages can have private +macros defined, that will not be called by accident. They can _only_ be +called through the builtin `indir'. + + One other point to observe is that argument collection occurs before +`indir' invokes NAME, so if argument collection changes the value of +NAME, that will be reflected in the final expansion. This is different +than the behavior when invoking macros directly, where the definition +that was in effect before argument collection is used. + + $ m4 -d + define(`f', `1') + => + f(define(`f', `2')) + =>1 + indir(`f', define(`f', `3')) + =>3 + indir(`f', undefine(`f')) + error-->m4:stdin:4: undefined macro `f' + => + + When handed the result of `defn' (*note Defn::) as one of its +arguments, `indir' defers to the invoked NAME for whether a token +representing a builtin is recognized or flattened to the empty string. + + $ m4 -d + indir(defn(`defn'), `divnum') + error-->m4:stdin:1: Warning: indir: invalid macro name ignored + => + indir(`define', defn(`defn'), `divnum') + error-->m4:stdin:2: Warning: define: invalid macro name ignored + => + indir(`define', `foo', defn(`divnum')) + => + foo + =>0 + indir(`divert', defn(`foo')) + error-->m4:stdin:5: empty string treated as 0 in builtin `divert' + => + + +File: m4.info, Node: Builtin, Prev: Indir, Up: Definitions + +5.8 Indirect call of builtins +============================= + +Builtin macros can be called indirectly with `builtin': + + -- Builtin: builtin (NAME, [ARGS...]) + Results in a call to the builtin NAME, which is passed the rest of + the arguments ARGS. If NAME does not name a builtin, an error + message is printed, and the expansion is void. + + The macro `builtin' is recognized only with parameters. + + This can be used even if NAME has been given another definition that +has covered the original, or been undefined so that no macro maps to +the builtin. + + pushdef(`define', `hidden') + => + undefine(`undefine') + => + define(`foo', `bar') + =>hidden + foo + =>foo + builtin(`define', `foo', defn(`divnum')) + => + foo + =>0 + builtin(`define', `foo', `BAR') + => + foo + =>BAR + undefine(`foo') + =>undefine(foo) + foo + =>BAR + builtin(`undefine', `foo') + => + foo + =>foo + + The NAME argument only matches the original name of the builtin, +even when the `--prefix-builtins' option (or `-P', *note Invoking m4: +Operation modes.) is in effect. This is different from `indir', which +only tracks current macro names. + + $ m4 -P + m4_builtin(`divnum') + =>0 + m4_builtin(`m4_divnum') + error-->m4:stdin:2: undefined builtin `m4_divnum' + => + m4_indir(`divnum') + error-->m4:stdin:3: undefined macro `divnum' + => + m4_indir(`m4_divnum') + =>0 + + Note that `indir' and `builtin' can be used to invoke builtins +without arguments, even when they normally require parameters to be +recognized; but it will provoke a warning, and result in a void +expansion. + + builtin + =>builtin + builtin() + error-->m4:stdin:2: undefined builtin `' + => + builtin(`builtin') + error-->m4:stdin:3: Warning: too few arguments to builtin `builtin' + => + builtin(`builtin',) + error-->m4:stdin:4: undefined builtin `' + => + builtin(`builtin', ``' + ') + error-->m4:stdin:5: undefined builtin ``' + error-->' + => + indir(`index') + error-->m4:stdin:7: Warning: too few arguments to builtin `index' + => + + +File: m4.info, Node: Conditionals, Next: Debugging, Prev: Definitions, Up: Top + +6 Conditionals, loops, and recursion +************************************ + +Macros, expanding to plain text, perhaps with arguments, are not quite +enough. We would like to have macros expand to different things, based +on decisions taken at run-time. For that, we need some kind of +conditionals. Also, we would like to have some kind of loop construct, +so we could do something a number of times, or while some condition is +true. + +* Menu: + +* Ifdef:: Testing if a macro is defined +* Ifelse:: If-else construct, or multibranch +* Shift:: Recursion in `m4' +* Forloop:: Iteration by counting +* Foreach:: Iteration by list contents +* Stacks:: Working with definition stacks +* Composition:: Building macros with macros + + +File: m4.info, Node: Ifdef, Next: Ifelse, Up: Conditionals + +6.1 Testing if a macro is defined +================================= + +There are two different builtin conditionals in `m4'. The first is +`ifdef': + + -- Builtin: ifdef (NAME, STRING-1, [STRING-2]) + If NAME is defined as a macro, `ifdef' expands to STRING-1, + otherwise to STRING-2. If STRING-2 is omitted, it is taken to be + the empty string (according to the normal rules). + + The macro `ifdef' is recognized only with parameters. + + ifdef(`foo', ``foo' is defined', ``foo' is not defined') + =>foo is not defined + define(`foo', `') + => + ifdef(`foo', ``foo' is defined', ``foo' is not defined') + =>foo is defined + ifdef(`no_such_macro', `yes', `no', `extra argument') + error-->m4:stdin:4: Warning: excess arguments to builtin `ifdef' ignored + =>no + + +File: m4.info, Node: Ifelse, Next: Shift, Prev: Ifdef, Up: Conditionals + +6.2 If-else construct, or multibranch +===================================== + +The other conditional, `ifelse', is much more powerful. It can be used +as a way to introduce a long comment, as an if-else construct, or as a +multibranch, depending on the number of arguments supplied: + + -- Builtin: ifelse (COMMENT) + -- Builtin: ifelse (STRING-1, STRING-2, EQUAL, [NOT-EQUAL]) + -- Builtin: ifelse (STRING-1, STRING-2, EQUAL-1, STRING-3, STRING-4, + EQUAL-2, ..., [NOT-EQUAL]) + Used with only one argument, the `ifelse' simply discards it and + produces no output. + + If called with three or four arguments, `ifelse' expands into + EQUAL, if STRING-1 and STRING-2 are equal (character for + character), otherwise it expands to NOT-EQUAL. A final fifth + argument is ignored, after triggering a warning. + + If called with six or more arguments, and STRING-1 and STRING-2 + are equal, `ifelse' expands into EQUAL-1, otherwise the first + three arguments are discarded and the processing starts again. + + The macro `ifelse' is recognized only with parameters. + + Using only one argument is a common `m4' idiom for introducing a +block comment, as an alternative to repeatedly using `dnl'. This +special usage is recognized by GNU `m4', so that in this case, the +warning about missing arguments is never triggered. + + ifelse(`some comments') + => + ifelse(`foo', `bar') + error-->m4:stdin:2: Warning: too few arguments to builtin `ifelse' + => + + Using three or four arguments provides decision points. + + ifelse(`foo', `bar', `true') + => + ifelse(`foo', `foo', `true') + =>true + define(`foo', `bar') + => + ifelse(foo, `bar', `true', `false') + =>true + ifelse(foo, `foo', `true', `false') + =>false + + Notice how the first argument was used unquoted; it is common to +compare the expansion of a macro with a string. With this macro, you +can now reproduce the behavior of blind builtins, where the macro is +recognized only with arguments. + + define(`foo', `ifelse(`$#', `0', ``$0'', `arguments:$#')') + => + foo + =>foo + foo() + =>arguments:1 + foo(`a', `b', `c') + =>arguments:3 + + For an example of a way to make defining blind macros easier, see +*note Composition::. + + The macro `ifelse' can take more than four arguments. If given more +than four arguments, `ifelse' works like a `case' or `switch' statement +in traditional programming languages. If STRING-1 and STRING-2 are +equal, `ifelse' expands into EQUAL-1, otherwise the procedure is +repeated with the first three arguments discarded. This calls for an +example: + + ifelse(`foo', `bar', `third', `gnu', `gnats') + error-->m4:stdin:1: Warning: excess arguments to builtin `ifelse' ignored + =>gnu + ifelse(`foo', `bar', `third', `gnu', `gnats', `sixth') + => + ifelse(`foo', `bar', `third', `gnu', `gnats', `sixth', `seventh') + =>seventh + ifelse(`foo', `bar', `3', `gnu', `gnats', `6', `7', `8') + error-->m4:stdin:4: Warning: excess arguments to builtin `ifelse' ignored + =>7 + + Naturally, the normal case will be slightly more advanced than these +examples. A common use of `ifelse' is in macros implementing loops of +various kinds. + + +File: m4.info, Node: Shift, Next: Forloop, Prev: Ifelse, Up: Conditionals + +6.3 Recursion in `m4' +===================== + +There is no direct support for loops in `m4', but macros can be +recursive. There is no limit on the number of recursion levels, other +than those enforced by your hardware and operating system. + + Loops can be programmed using recursion and the conditionals +described previously. + + There is a builtin macro, `shift', which can, among other things, be +used for iterating through the actual arguments to a macro: + + -- Builtin: shift (ARG1, ...) + Takes any number of arguments, and expands to all its arguments + except ARG1, separated by commas, with each argument quoted. + + The macro `shift' is recognized only with parameters. + + shift + =>shift + shift(`bar') + => + shift(`foo', `bar', `baz') + =>bar,baz + + An example of the use of `shift' is this macro: + + -- Composite: reverse (...) + Takes any number of arguments, and reverses their order. + + It is implemented as: + + define(`reverse', `ifelse(`$#', `0', , `$#', `1', ``$1'', + `reverse(shift($@)), `$1'')') + => + reverse + => + reverse(`foo') + =>foo + reverse(`foo', `bar', `gnats', `and gnus') + =>and gnus, gnats, bar, foo + + While not a very interesting macro, it does show how simple loops +can be made with `shift', `ifelse' and recursion. It also shows that +`shift' is usually used with `$@'. Another example of this is an +implementation of a short-circuiting conditional operator. + + -- Composite: cond (TEST-1, STRING-1, EQUAL-1, [TEST-2], [STRING-2], + [EQUAL-2], ..., [NOT-EQUAL]) + Similar to `ifelse', where an equal comparison between the first + two strings results in the third, otherwise the first three + arguments are discarded and the process repeats. The difference + is that each TEST-<N> is expanded only when it is encountered. + This means that every third argument to `cond' is normally given + one more level of quoting than the corresponding argument to + `ifelse'. + + Here is the implementation of `cond', along with a demonstration of +how it can short-circuit the side effects in `side'. Notice how all +the unquoted side effects happen regardless of how many comparisons are +made with `ifelse', compared with only the relevant effects with `cond'. + + define(`cond', + `ifelse(`$#', `1', `$1', + `ifelse($1, `$2', `$3', + `$0(shift(shift(shift($@))))')')')dnl + define(`side', `define(`counter', incr(counter))$1')dnl + define(`example1', + `define(`counter', `0')dnl + ifelse(side(`$1'), `yes', `one comparison: ', + side(`$1'), `no', `two comparisons: ', + side(`$1'), `maybe', `three comparisons: ', + `side(`default answer: ')')counter')dnl + define(`example2', + `define(`counter', `0')dnl + cond(`side(`$1')', `yes', `one comparison: ', + `side(`$1')', `no', `two comparisons: ', + `side(`$1')', `maybe', `three comparisons: ', + `side(`default answer: ')')counter')dnl + example1(`yes') + =>one comparison: 3 + example1(`no') + =>two comparisons: 3 + example1(`maybe') + =>three comparisons: 3 + example1(`feeling rather indecisive today') + =>default answer: 4 + example2(`yes') + =>one comparison: 1 + example2(`no') + =>two comparisons: 2 + example2(`maybe') + =>three comparisons: 3 + example2(`feeling rather indecisive today') + =>default answer: 4 + + Another common task that requires iteration is joining a list of +arguments into a single string. + + -- Composite: join ([SEPARATOR], [ARGS...]) + -- Composite: joinall ([SEPARATOR], [ARGS...]) + Generate a single-quoted string, consisting of each ARG separated + by SEPARATOR. While `joinall' always outputs a SEPARATOR between + arguments, `join' avoids the SEPARATOR for an empty ARG. + + Here are some examples of its usage, based on the implementation +`m4-1.4.16/examples/join.m4' distributed in this package: + + $ m4 -I examples + include(`join.m4') + => + join,join(`-'),join(`-', `'),join(`-', `', `') + =>,,, + joinall,joinall(`-'),joinall(`-', `'),joinall(`-', `', `') + =>,,,- + join(`-', `1') + =>1 + join(`-', `1', `2', `3') + =>1-2-3 + join(`', `1', `2', `3') + =>123 + join(`-', `', `1', `', `', `2', `') + =>1-2 + joinall(`-', `', `1', `', `', `2', `') + =>-1---2- + join(`,', `1', `2', `3') + =>1,2,3 + define(`nargs', `$#')dnl + nargs(join(`,', `1', `2', `3')) + =>1 + + Examining the implementation shows some interesting points about +several m4 programming idioms. + + $ m4 -I examples + undivert(`join.m4')dnl + =>divert(`-1') + =># join(sep, args) - join each non-empty ARG into a single + =># string, with each element separated by SEP + =>define(`join', + =>`ifelse(`$#', `2', ``$2'', + => `ifelse(`$2', `', `', ``$2'_')$0(`$1', shift(shift($@)))')') + =>define(`_join', + =>`ifelse(`$#$2', `2', `', + => `ifelse(`$2', `', `', ``$1$2'')$0(`$1', shift(shift($@)))')') + =># joinall(sep, args) - join each ARG, including empty ones, + =># into a single string, with each element separated by SEP + =>define(`joinall', ``$2'_$0(`$1', shift($@))') + =>define(`_joinall', + =>`ifelse(`$#', `2', `', ``$1$3'$0(`$1', shift(shift($@)))')') + =>divert`'dnl + + First, notice that this implementation creates helper macros `_join' +and `_joinall'. This division of labor makes it easier to output the +correct number of SEPARATOR instances: `join' and `joinall' are +responsible for the first argument, without a separator, while `_join' +and `_joinall' are responsible for all remaining arguments, always +outputting a separator when outputting an argument. + + Next, observe how `join' decides to iterate to itself, because the +first ARG was empty, or to output the argument and swap over to +`_join'. If the argument is non-empty, then the nested `ifelse' +results in an unquoted `_', which is concatenated with the `$0' to form +the next macro name to invoke. The `joinall' implementation is simpler +since it does not have to suppress empty ARG; it always executes once +then defers to `_joinall'. + + Another important idiom is the idea that SEPARATOR is reused for +each iteration. Each iteration has one less argument, but rather than +discarding `$1' by iterating with `$0(shift($@))', the macro discards +`$2' by using `$0(`$1', shift(shift($@)))'. + + Next, notice that it is possible to compare more than one condition +in a single `ifelse' test. The test of `$#$2' against `2' allows +`_join' to iterate for two separate reasons--either there are still +more than two arguments, or there are exactly two arguments but the +last argument is not empty. + + Finally, notice that these macros require exactly two arguments to +terminate recursion, but that they still correctly result in empty +output when given no ARGS (i.e., zero or one macro argument). On the +first pass when there are too few arguments, the `shift' results in no +output, but leaves an empty string to serve as the required second +argument for the second pass. Put another way, ``$1', shift($@)' is +not the same as `$@', since only the former guarantees at least two +arguments. + + Sometimes, a recursive algorithm requires adding quotes to each +element, or treating multiple arguments as a single element: + + -- Composite: quote (...) + -- Composite: dquote (...) + -- Composite: dquote_elt (...) + Takes any number of arguments, and adds quoting. With `quote', + only one level of quoting is added, effectively removing whitespace + after commas and turning multiple arguments into a single string. + With `dquote', two levels of quoting are added, one around each + element, and one around the list. And with `dquote_elt', two + levels of quoting are added around each element. + + An actual implementation of these three macros is distributed as +`m4-1.4.16/examples/quote.m4' in this package. First, let's examine +their usage: + + $ m4 -I examples + include(`quote.m4') + => + -quote-dquote-dquote_elt- + =>---- + -quote()-dquote()-dquote_elt()- + =>--`'-`'- + -quote(`1')-dquote(`1')-dquote_elt(`1')- + =>-1-`1'-`1'- + -quote(`1', `2')-dquote(`1', `2')-dquote_elt(`1', `2')- + =>-1,2-`1',`2'-`1',`2'- + define(`n', `$#')dnl + -n(quote(`1', `2'))-n(dquote(`1', `2'))-n(dquote_elt(`1', `2'))- + =>-1-1-2- + dquote(dquote_elt(`1', `2')) + =>``1'',``2'' + dquote_elt(dquote(`1', `2')) + =>``1',`2'' + + The last two lines show that when given two arguments, `dquote' +results in one string, while `dquote_elt' results in two. Now, examine +the implementation. Note that `quote' and `dquote_elt' make decisions +based on their number of arguments, so that when called without +arguments, they result in nothing instead of a quoted empty string; +this is so that it is possible to distinguish between no arguments and +an empty first argument. `dquote', on the other hand, results in a +string no matter what, since it is still possible to tell whether it +was invoked without arguments based on the resulting string. + + $ m4 -I examples + undivert(`quote.m4')dnl + =>divert(`-1') + =># quote(args) - convert args to single-quoted string + =>define(`quote', `ifelse(`$#', `0', `', ``$*'')') + =># dquote(args) - convert args to quoted list of quoted strings + =>define(`dquote', ``$@'') + =># dquote_elt(args) - convert args to list of double-quoted strings + =>define(`dquote_elt', `ifelse(`$#', `0', `', `$#', `1', ```$1''', + => ```$1'',$0(shift($@))')') + =>divert`'dnl + + It is worth pointing out that `quote(ARGS)' is more efficient than +`joinall(`,', ARGS)' for producing the same output. + + One more useful macro based on `shift' allows portably selecting an +arbitrary argument (usually greater than the ninth argument), without +relying on the GNU extension of multi-digit arguments (*note +Arguments::). + + -- Composite: argn (N, ...) + Expands to argument N out of the remaining arguments. N must be a + positive number. Usually invoked as `argn(`N',$@)'. + + It is implemented as: + + define(`argn', `ifelse(`$1', 1, ``$2'', + `argn(decr(`$1'), shift(shift($@)))')') + => + argn(`1', `a') + =>a + define(`foo', `argn(`11', $@)') + => + foo(`a', `b', `c', `d', `e', `f', `g', `h', `i', `j', `k', `l') + =>k + + +File: m4.info, Node: Forloop, Next: Foreach, Prev: Shift, Up: Conditionals + +6.4 Iteration by counting +========================= + +Here is an example of a loop macro that implements a simple for loop. + + -- Composite: forloop (ITERATOR, START, END, TEXT) + Takes the name in ITERATOR, which must be a valid macro name, and + successively assign it each integer value from START to END, + inclusive. For each assignment to ITERATOR, append TEXT to the + expansion of the `forloop'. TEXT may refer to ITERATOR. Any + definition of ITERATOR prior to this invocation is restored. + + It can, for example, be used for simple counting: + + $ m4 -I examples + include(`forloop.m4') + => + forloop(`i', `1', `8', `i ') + =>1 2 3 4 5 6 7 8 + + For-loops can be nested, like: + + $ m4 -I examples + include(`forloop.m4') + => + forloop(`i', `1', `4', `forloop(`j', `1', `8', ` (i, j)') + ') + => (1, 1) (1, 2) (1, 3) (1, 4) (1, 5) (1, 6) (1, 7) (1, 8) + => (2, 1) (2, 2) (2, 3) (2, 4) (2, 5) (2, 6) (2, 7) (2, 8) + => (3, 1) (3, 2) (3, 3) (3, 4) (3, 5) (3, 6) (3, 7) (3, 8) + => (4, 1) (4, 2) (4, 3) (4, 4) (4, 5) (4, 6) (4, 7) (4, 8) + => + + The implementation of the `forloop' macro is fairly straightforward. +The `forloop' macro itself is simply a wrapper, which saves the +previous definition of the first argument, calls the internal macro +`_forloop', and re-establishes the saved definition of the first +argument. + + The macro `_forloop' expands the fourth argument once, and tests to +see if the iterator has reached the final value. If it has not +finished, it increments the iterator (using the predefined macro +`incr', *note Incr::), and recurses. + + Here is an actual implementation of `forloop', distributed as +`m4-1.4.16/examples/forloop.m4' in this package: + + $ m4 -I examples + undivert(`forloop.m4')dnl + =>divert(`-1') + =># forloop(var, from, to, stmt) - simple version + =>define(`forloop', `pushdef(`$1', `$2')_forloop($@)popdef(`$1')') + =>define(`_forloop', + => `$4`'ifelse($1, `$3', `', `define(`$1', incr($1))$0($@)')') + =>divert`'dnl + + Notice the careful use of quotes. Certain macro arguments are left +unquoted, each for its own reason. Try to find out _why_ these +arguments are left unquoted, and see what happens if they are quoted. +(As presented, these two macros are useful but not very robust for +general use. They lack even basic error handling for cases like START +less than END, END not numeric, or ITERATOR not being a macro name. +See if you can improve these macros; or *note Answers: Improved +forloop.). + + +File: m4.info, Node: Foreach, Next: Stacks, Prev: Forloop, Up: Conditionals + +6.5 Iteration by list contents +============================== + +Here is an example of a loop macro that implements list iteration. + + -- Composite: foreach (ITERATOR, PAREN-LIST, TEXT) + -- Composite: foreachq (ITERATOR, QUOTE-LIST, TEXT) + Takes the name in ITERATOR, which must be a valid macro name, and + successively assign it each value from PAREN-LIST or QUOTE-LIST. + In `foreach', PAREN-LIST is a comma-separated list of elements + contained in parentheses. In `foreachq', QUOTE-LIST is a + comma-separated list of elements contained in a quoted string. + For each assignment to ITERATOR, append TEXT to the overall + expansion. TEXT may refer to ITERATOR. Any definition of + ITERATOR prior to this invocation is restored. + + As an example, this displays each word in a list inside of a +sentence, using an implementation of `foreach' distributed as +`m4-1.4.16/examples/foreach.m4', and `foreachq' in +`m4-1.4.16/examples/foreachq.m4'. + + $ m4 -I examples + include(`foreach.m4') + => + foreach(`x', (foo, bar, foobar), `Word was: x + ')dnl + =>Word was: foo + =>Word was: bar + =>Word was: foobar + include(`foreachq.m4') + => + foreachq(`x', `foo, bar, foobar', `Word was: x + ')dnl + =>Word was: foo + =>Word was: bar + =>Word was: foobar + + It is possible to be more complex; each element of the PAREN-LIST or +QUOTE-LIST can itself be a list, to pass as further arguments to a +helper macro. This example generates a shell case statement: + + $ m4 -I examples + include(`foreach.m4') + => + define(`_case', ` $1) + $2=" $1";; + ')dnl + define(`_cat', `$1$2')dnl + case $`'1 in + =>case $1 in + foreach(`x', `(`(`a', `vara')', `(`b', `varb')', `(`c', `varc')')', + `_cat(`_case', x)')dnl + => a) + => vara=" a";; + => b) + => varb=" b";; + => c) + => varc=" c";; + esac + =>esac + + The implementation of the `foreach' macro is a bit more involved; it +is a wrapper around two helper macros. First, `_arg1' is needed to +grab the first element of a list. Second, `_foreach' implements the +recursion, successively walking through the original list. Here is a +simple implementation of `foreach': + + $ m4 -I examples + undivert(`foreach.m4')dnl + =>divert(`-1') + =># foreach(x, (item_1, item_2, ..., item_n), stmt) + =># parenthesized list, simple version + =>define(`foreach', `pushdef(`$1')_foreach($@)popdef(`$1')') + =>define(`_arg1', `$1') + =>define(`_foreach', `ifelse(`$2', `()', `', + => `define(`$1', _arg1$2)$3`'$0(`$1', (shift$2), `$3')')') + =>divert`'dnl + + Unfortunately, that implementation is not robust to macro names as +list elements. Each iteration of `_foreach' is stripping another layer +of quotes, leading to erratic results if list elements are not already +fully expanded. The first cut at implementing `foreachq' takes this +into account. Also, when using quoted elements in a PAREN-LIST, the +overall list must be quoted. A QUOTE-LIST has the nice property of +requiring fewer characters to create a list containing the same quoted +elements. To see the difference between the two macros, we attempt to +pass double-quoted macro names in a list, expecting the macro name on +output after one layer of quotes is removed during list iteration and +the final layer removed during the final rescan: + + $ m4 -I examples + define(`a', `1')define(`b', `2')define(`c', `3') + => + include(`foreach.m4') + => + include(`foreachq.m4') + => + foreach(`x', `(``a'', ``(b'', ``c)'')', `x + ') + =>1 + =>(2)1 + => + =>, x + =>) + foreachq(`x', ```a'', ``(b'', ``c)''', `x + ')dnl + =>a + =>(b + =>c) + + Obviously, `foreachq' did a better job; here is its implementation: + + $ m4 -I examples + undivert(`foreachq.m4')dnl + =>include(`quote.m4')dnl + =>divert(`-1') + =># foreachq(x, `item_1, item_2, ..., item_n', stmt) + =># quoted list, simple version + =>define(`foreachq', `pushdef(`$1')_foreachq($@)popdef(`$1')') + =>define(`_arg1', `$1') + =>define(`_foreachq', `ifelse(quote($2), `', `', + => `define(`$1', `_arg1($2)')$3`'$0(`$1', `shift($2)', `$3')')') + =>divert`'dnl + + Notice that `_foreachq' had to use the helper macro `quote' defined +earlier (*note Shift::), to ensure that the embedded `ifelse' call does +not go haywire if a list element contains a comma. Unfortunately, this +implementation of `foreachq' has its own severe flaw. Whereas the +`foreach' implementation was linear, this macro is quadratic in the +number of list elements, and is much more likely to trip up the limit +set by the command line option `--nesting-limit' (or `-L', *note +Invoking m4: Limits control.). Additionally, this implementation does +not expand `defn(`ITERATOR')' very well, when compared with `foreach'. + + $ m4 -I examples + include(`foreach.m4')include(`foreachq.m4') + => + foreach(`name', `(`a', `b')', ` defn(`name')') + => a b + foreachq(`name', ``a', `b'', ` defn(`name')') + => _arg1(`a', `b') _arg1(shift(`a', `b')) + + It is possible to have robust iteration with linear behavior and sane +ITERATOR contents for either list style. See if you can learn from the +best elements of both of these implementations to create robust macros +(or *note Answers: Improved foreach.). + + +File: m4.info, Node: Stacks, Next: Composition, Prev: Foreach, Up: Conditionals + +6.6 Working with definition stacks +================================== + +Thanks to `pushdef', manipulation of a stack is an intrinsic operation +in `m4'. Normally, only the topmost definition in a stack is +important, but sometimes, it is desirable to manipulate the entire +definition stack. + + -- Composite: stack_foreach (MACRO, ACTION) + -- Composite: stack_foreach_lifo (MACRO, ACTION) + For each of the `pushdef' definitions associated with MACRO, + invoke the macro ACTION with a single argument of that definition. + `stack_foreach' visits the oldest definition first, while + `stack_foreach_lifo' visits the current definition first. ACTION + should not modify or dereference MACRO. There are a few special + macros, such as `defn', which cannot be used as the MACRO + parameter. + + A sample implementation of these macros is distributed in the file +`m4-1.4.16/examples/stack.m4'. + + $ m4 -I examples + include(`stack.m4') + => + pushdef(`a', `1')pushdef(`a', `2')pushdef(`a', `3') + => + define(`show', ``$1' + ') + => + stack_foreach(`a', `show')dnl + =>1 + =>2 + =>3 + stack_foreach_lifo(`a', `show')dnl + =>3 + =>2 + =>1 + + Now for the implementation. Note the definition of a helper macro, +`_stack_reverse', which destructively swaps the contents of one stack +of definitions into the reverse order in the temporary macro `tmp-$1'. +By calling the helper twice, the original order is restored back into +the macro `$1'; since the operation is destructive, this explains why +`$1' must not be modified or dereferenced during the traversal. The +caller can then inject additional code to pass the definition currently +being visited to `$2'. The choice of helper names is intentional; +since `-' is not valid as part of a macro name, there is no risk of +conflict with a valid macro name, and the code is guaranteed to use +`defn' where necessary. Finally, note that any macro used in the +traversal of a `pushdef' stack, such as `pushdef' or `defn', cannot be +handled by `stack_foreach', since the macro would temporarily be +undefined during the algorithm. + + $ m4 -I examples + undivert(`stack.m4')dnl + =>divert(`-1') + =># stack_foreach(macro, action) + =># Invoke ACTION with a single argument of each definition + =># from the definition stack of MACRO, starting with the oldest. + =>define(`stack_foreach', + =>`_stack_reverse(`$1', `tmp-$1')'dnl + =>`_stack_reverse(`tmp-$1', `$1', `$2(defn(`$1'))')') + =># stack_foreach_lifo(macro, action) + =># Invoke ACTION with a single argument of each definition + =># from the definition stack of MACRO, starting with the newest. + =>define(`stack_foreach_lifo', + =>`_stack_reverse(`$1', `tmp-$1', `$2(defn(`$1'))')'dnl + =>`_stack_reverse(`tmp-$1', `$1')') + =>define(`_stack_reverse', + =>`ifdef(`$1', `pushdef(`$2', defn(`$1'))$3`'popdef(`$1')$0($@)')') + =>divert`'dnl + + +File: m4.info, Node: Composition, Prev: Stacks, Up: Conditionals + +6.7 Building macros with macros +=============================== + +Since m4 is a macro language, it is possible to write macros that can +build other macros. First on the list is a way to automate the +creation of blind macros. + + -- Composite: define_blind (NAME, [VALUE]) + Defines NAME as a blind macro, such that NAME will expand to VALUE + only when given explicit arguments. VALUE should not be the + result of `defn' (*note Defn::). This macro is only recognized + with parameters, and results in an empty string. + + Defining a macro to define another macro can be a bit tricky. We +want to use a literal `$#' in the argument to the nested `define'. +However, if `$' and `#' are adjacent in the definition of +`define_blind', then it would be expanded as the number of arguments to +`define_blind' rather than the intended number of arguments to NAME. +The solution is to pass the difficult characters through extra +arguments to a helper macro `_define_blind'. When composing macros, it +is a common idiom to need a helper macro to concatenate text that forms +parameters in the composed macro, rather than interpreting the text as +a parameter of the composing macro. + + As for the limitation against using `defn', there are two reasons. +If a macro was previously defined with `define_blind', then it can +safely be renamed to a new blind macro using plain `define'; using +`define_blind' to rename it just adds another layer of `ifelse', +occupying memory and slowing down execution. And if a macro is a +builtin, then it would result in an attempt to define a macro +consisting of both text and a builtin token; this is not supported, and +the builtin token is flattened to an empty string. + + With that explanation, here's the definition, and some sample usage. +Notice that `define_blind' is itself a blind macro. + + $ m4 -d + define(`define_blind', `ifelse(`$#', `0', ``$0'', + `_$0(`$1', `$2', `$'`#', `$'`0')')') + => + define(`_define_blind', `define(`$1', + `ifelse(`$3', `0', ``$4'', `$2')')') + => + define_blind + =>define_blind + define_blind(`foo', `arguments were $*') + => + foo + =>foo + foo(`bar') + =>arguments were bar + define(`blah', defn(`foo')) + => + blah + =>blah + blah(`a', `b') + =>arguments were a,b + defn(`blah') + =>ifelse(`$#', `0', ``$0'', `arguments were $*') + + Another interesting composition tactic is argument "currying", or +factoring a macro that takes multiple arguments for use in a context +that provides exactly one argument. + + -- Composite: curry (MACRO, ...) + Expand to a macro call that takes exactly one argument, then + appends that argument to the original arguments and invokes MACRO + with the resulting list of arguments. + + A demonstration of currying makes the intent of this macro a little +more obvious. The macro `stack_foreach' mentioned earlier is an example +of a context that provides exactly one argument to a macro name. But +coupled with currying, we can invoke `reverse' with two arguments for +each definition of a macro stack. This example uses the file +`m4-1.4.16/examples/curry.m4' included in the distribution. + + $ m4 -I examples + include(`curry.m4')include(`stack.m4') + => + define(`reverse', `ifelse(`$#', `0', , `$#', `1', ``$1'', + `reverse(shift($@)), `$1'')') + => + pushdef(`a', `1')pushdef(`a', `2')pushdef(`a', `3') + => + stack_foreach(`a', `:curry(`reverse', `4')') + =>:1, 4:2, 4:3, 4 + curry(`curry', `reverse', `1')(`2')(`3') + =>3, 2, 1 + + Now for the implementation. Notice how `curry' leaves off with a +macro name but no open parenthesis, while still in the middle of +collecting arguments for `$1'. The macro `_curry' is the helper macro +that takes one argument, then adds it to the list and finally supplies +the closing parenthesis. The use of a comma inside the `shift' call +allows currying to also work for a macro that takes one argument, +although it often makes more sense to invoke that macro directly rather +than going through `curry'. + + $ m4 -I examples + undivert(`curry.m4')dnl + =>divert(`-1') + =># curry(macro, args) + =># Expand to a macro call that takes one argument, then invoke + =># macro(args, extra). + =>define(`curry', `$1(shift($@,)_$0') + =>define(`_curry', ``$1')') + =>divert`'dnl + + Unfortunately, with M4 1.4.x, `curry' is unable to handle builtin +tokens, which are silently flattened to the empty string when passed +through another text macro. This limitation will be lifted in a future +release of M4. + + Putting the last few concepts together, it is possible to copy or +rename an entire stack of macro definitions. + + -- Composite: copy (SOURCE, DEST) + -- Composite: rename (SOURCE, DEST) + Ensure that DEST is undefined, then define it to the same stack of + definitions currently in SOURCE. `copy' leaves SOURCE unchanged, + while `rename' undefines SOURCE. There are only a few macros, + such as `copy' or `defn', which cannot be copied via this macro. + + The implementation is relatively straightforward (although since it +uses `curry', it is unable to copy builtin macros, such as the second +definition of `a' as a synonym for `divnum'. See if you can design a +version that works around this limitation, or *note Answers: Improved +copy.). + + $ m4 -I examples + include(`curry.m4')include(`stack.m4') + => + define(`rename', `copy($@)undefine(`$1')')dnl + define(`copy', `ifdef(`$2', `errprint(`$2 already defined + ')m4exit(`1')', + `stack_foreach(`$1', `curry(`pushdef', `$2')')')')dnl + pushdef(`a', `1')pushdef(`a', defn(`divnum'))pushdef(`a', `2') + => + copy(`a', `b') + => + rename(`b', `c') + => + a b c + =>2 b 2 + popdef(`a', `c')c a + => 0 + popdef(`a', `c')a c + =>1 1 + + +File: m4.info, Node: Debugging, Next: Input Control, Prev: Conditionals, Up: Top + +7 How to debug macros and input +******************************* + +When writing macros for `m4', they often do not work as intended on the +first try (as is the case with most programming languages). +Fortunately, there is support for macro debugging in `m4'. + +* Menu: + +* Dumpdef:: Displaying macro definitions +* Trace:: Tracing macro calls +* Debug Levels:: Controlling debugging output +* Debug Output:: Saving debugging output + + +File: m4.info, Node: Dumpdef, Next: Trace, Up: Debugging + +7.1 Displaying macro definitions +================================ + +If you want to see what a name expands into, you can use the builtin +`dumpdef': + + -- Builtin: dumpdef ([NAMES...]) + Accepts any number of arguments. If called without any arguments, + it displays the definitions of all known names, otherwise it + displays the definitions of the NAMES given. The output is + printed to the current debug file (usually standard error), and is + sorted by name. If an unknown name is encountered, a warning is + printed. + + The expansion of `dumpdef' is void. + + $ m4 -d + define(`foo', `Hello world.') + => + dumpdef(`foo') + error-->foo: `Hello world.' + => + dumpdef(`define') + error-->define: <define> + => + + The last example shows how builtin macros definitions are displayed. +The definition that is dumped corresponds to what would occur if the +macro were to be called at that point, even if other definitions are +still live due to redefining a macro during argument collection. + + $ m4 -d + pushdef(`f', ``$0'1')pushdef(`f', ``$0'2') + => + f(popdef(`f')dumpdef(`f')) + error-->f: ``$0'1' + =>f2 + f(popdef(`f')dumpdef(`f')) + error-->m4:stdin:3: undefined macro `f' + =>f1 + + *Note Debug Levels::, for information on controlling the details of +the display. + + +File: m4.info, Node: Trace, Next: Debug Levels, Prev: Dumpdef, Up: Debugging + +7.2 Tracing macro calls +======================= + +It is possible to trace macro calls and expansions through the builtins +`traceon' and `traceoff': + + -- Builtin: traceon ([NAMES...]) + -- Builtin: traceoff ([NAMES...]) + When called without any arguments, `traceon' and `traceoff' will + turn tracing on and off, respectively, for all currently defined + macros. + + When called with arguments, only the macros listed in NAMES are + affected, whether or not they are currently defined. + + The expansion of `traceon' and `traceoff' is void. + + Whenever a traced macro is called and the arguments have been +collected, the call is displayed. If the expansion of the macro call +is not void, the expansion can be displayed after the call. The output +is printed to the current debug file (defaulting to standard error, +*note Debug Output::). + + $ m4 -d + define(`foo', `Hello World.') + => + define(`echo', `$@') + => + traceon(`foo', `echo') + => + foo + error-->m4trace: -1- foo -> `Hello World.' + =>Hello World. + echo(`gnus', `and gnats') + error-->m4trace: -1- echo(`gnus', `and gnats') -> ``gnus',`and gnats'' + =>gnus,and gnats + + The number between dashes is the depth of the expansion. It is one +most of the time, signifying an expansion at the outermost level, but it +increases when macro arguments contain unquoted macro calls. The +maximum number that will appear between dashes is controlled by the +option `--nesting-limit' (or `-L', *note Invoking m4: Limits control.). +Additionally, the option `--trace' (or `-t') can be used to invoke +`traceon(NAME)' before parsing input. + + $ m4 -L 3 -t ifelse + ifelse(`one level') + error-->m4trace: -1- ifelse + => + ifelse(ifelse(ifelse(`three levels'))) + error-->m4trace: -3- ifelse + error-->m4trace: -2- ifelse + error-->m4trace: -1- ifelse + => + ifelse(ifelse(ifelse(ifelse(`four levels')))) + error-->m4:stdin:3: recursion limit of 3 exceeded, use -L<N> to change it + + Tracing by name is an attribute that is preserved whether the macro +is defined or not. This allows the selection of macros to trace before +those macros are defined. + + $ m4 -d + traceoff(`foo') + => + traceon(`foo') + => + foo + =>foo + defn(`foo') + => + define(`foo', `bar') + => + foo + error-->m4trace: -1- foo -> `bar' + =>bar + undefine(`foo') + => + ifdef(`foo', `yes', `no') + =>no + indir(`foo') + error-->m4:stdin:9: undefined macro `foo' + => + define(`foo', `blah') + => + foo + error-->m4trace: -1- foo -> `blah' + =>blah + traceoff + => + foo + =>blah + + Tracing even works on builtins. However, `defn' (*note Defn::) does +not transfer tracing status. + + $ m4 -d + traceon(`traceon') + => + traceon(`traceoff') + error-->m4trace: -1- traceon(`traceoff') + => + traceoff(`traceoff') + error-->m4trace: -1- traceoff(`traceoff') + => + traceoff(`traceon') + => + traceon(`eval', `m4_divnum') + => + define(`m4_eval', defn(`eval')) + => + define(`m4_divnum', defn(`divnum')) + => + eval(divnum) + error-->m4trace: -1- eval(`0') -> `0' + =>0 + m4_eval(m4_divnum) + error-->m4trace: -2- m4_divnum -> `0' + =>0 + + *Note Debug Levels::, for information on controlling the details of +the display. The format of the trace output is not specified by POSIX, +and varies between implementations of `m4'. + + +File: m4.info, Node: Debug Levels, Next: Debug Output, Prev: Trace, Up: Debugging + +7.3 Controlling debugging output +================================ + +The `-d' option to `m4' (or `--debug', *note Invoking m4: Debugging +options.) controls the amount of details presented in three categories +of output. Trace output is requested by `traceon' (*note Trace::), and +each line is prefixed by `m4trace:' in relation to a macro invocation. +Debug output tracks useful events not associated with a macro +invocation, and each line is prefixed by `m4debug:'. Finally, +`dumpdef' (*note Dumpdef::) output is affected, with no prefix added to +the output lines. + + The FLAGS following the option can be one or more of the following: + +`a' + In trace output, show the actual arguments that were collected + before invoking the macro. This applies to all macro calls if the + `t' flag is used, otherwise only the macros covered by calls of + `traceon'. Arguments are subject to length truncation specified by + the command line option `--arglength' (or `-l'). + +`c' + In trace output, show several trace lines for each macro call. A + line is shown when the macro is seen, but before the arguments are + collected; a second line when the arguments have been collected + and a third line after the call has completed. + +`e' + In trace output, show the expansion of each macro call, if it is + not void. This applies to all macro calls if the `t' flag is used, + otherwise only the macros covered by calls of `traceon'. The + expansion is subject to length truncation specified by the command + line option `--arglength' (or `-l'). + +`f' + In debug and trace output, include the name of the current input + file in the output line. + +`i' + In debug output, print a message each time the current input file + is changed. + +`l' + In debug and trace output, include the current input line number + in the output line. + +`p' + In debug output, print a message when a named file is found + through the path search mechanism (*note Search Path::), giving + the actual file name used. + +`q' + In trace and dumpdef output, quote actual arguments and macro + expansions in the display with the current quotes. This is useful + in connection with the `a' and `e' flags above. + +`t' + In trace output, trace all macro calls made in this invocation of + `m4', regardless of the settings of `traceon'. + +`x' + In trace output, add a unique `macro call id' to each line of the + trace output. This is useful in connection with the `c' flag + above. + +`V' + A shorthand for all of the above flags. + + If no flags are specified with the `-d' option, the default is +`aeq'. The examples throughout this manual assume the default flags. + + There is a builtin macro `debugmode', which allows on-the-fly +control of the debugging output format: + + -- Builtin: debugmode ([FLAGS]) + The argument FLAGS should be a subset of the letters listed above. + As special cases, if the argument starts with a `+', the flags are + added to the current debug flags, and if it starts with a `-', they + are removed. If no argument is present, all debugging flags are + cleared (as if no `-d' was given), and with an empty argument the + flags are reset to the default of `aeq'. + + The expansion of `debugmode' is void. + + $ m4 + define(`foo', `FOO') + => + traceon(`foo') + => + debugmode() + => + foo + error-->m4trace: -1- foo -> `FOO' + =>FOO + debugmode + => + foo + error-->m4trace: -1- foo + =>FOO + debugmode(`+l') + => + foo + error-->m4trace:8: -1- foo + =>FOO + + The following example demonstrates the behavior of length truncation, +when specified on the command line. Note that each argument and the +final result are individually truncated. Also, the special tokens for +builtin functions are not truncated. + + $ m4 -d -l 6 + define(`echo', `$@')debugmode(`+t') + => + echo(`1', `long string') + error-->m4trace: -1- echo(`1', `long s...') -> ``1',`l...' + =>1,long string + indir(`echo', defn(`changequote')) + error-->m4trace: -2- defn(`change...') + error-->m4trace: -1- indir(`echo', <changequote>) -> ``'' + => + + This example shows the effects of the debug flags that are not +related to macro tracing. + + $ m4 -dip -I examples + error-->m4debug: input read from stdin + include(`foo')dnl + error-->m4debug: path search for `foo' found `examples/foo' + error-->m4debug: input read from examples/foo + =>bar + error-->m4debug: input reverted to stdin, line 1 + ^D + error-->m4debug: input exhausted + + +File: m4.info, Node: Debug Output, Prev: Debug Levels, Up: Debugging + +7.4 Saving debugging output +=========================== + +Debug and tracing output can be redirected to files using either the +`--debugfile' option to `m4' (*note Invoking m4: Debugging options.), +or with the builtin macro `debugfile': + + -- Builtin: debugfile ([FILE]) + Sends all further debug and trace output to FILE, opened in append + mode. If FILE is the empty string, debug and trace output are + discarded. If `debugfile' is called without any arguments, debug + and trace output are sent to standard error. This does not affect + warnings, error messages, or `errprint' output, which are always + sent to standard error. If FILE cannot be opened, the current + debug file is unchanged, and an error is issued. + + The expansion of `debugfile' is void. + + $ m4 -d + traceon(`divnum') + => + divnum(`extra') + error-->m4:stdin:2: Warning: excess arguments to builtin `divnum' ignored + error-->m4trace: -1- divnum(`extra') -> `0' + =>0 + debugfile() + => + divnum(`extra') + error-->m4:stdin:4: Warning: excess arguments to builtin `divnum' ignored + =>0 + debugfile + => + divnum + error-->m4trace: -1- divnum -> `0' + =>0 + + +File: m4.info, Node: Input Control, Next: File Inclusion, Prev: Debugging, Up: Top + +8 Input control +*************** + +This chapter describes various builtin macros for controlling the input +to `m4'. + +* Menu: + +* Dnl:: Deleting whitespace in input +* Changequote:: Changing the quote characters +* Changecom:: Changing the comment delimiters +* Changeword:: Changing the lexical structure of words +* M4wrap:: Saving text until end of input + + +File: m4.info, Node: Dnl, Next: Changequote, Up: Input Control + +8.1 Deleting whitespace in input +================================ + +The builtin `dnl' stands for "Discard to Next Line": + + -- Builtin: dnl + All characters, up to and including the next newline, are discarded + without performing any macro expansion. A warning is issued if + the end of the file is encountered without a newline. + + The expansion of `dnl' is void. + + It is often used in connection with `define', to remove the newline +that follows the call to `define'. Thus + + define(`foo', `Macro `foo'.')dnl A very simple macro, indeed. + foo + =>Macro foo. + + The input up to and including the next newline is discarded, as +opposed to the way comments are treated (*note Comments::). + + Usually, `dnl' is immediately followed by an end of line or some +other whitespace. GNU `m4' will produce a warning diagnostic if `dnl' +is followed by an open parenthesis. In this case, `dnl' will collect +and process all arguments, looking for a matching close parenthesis. +All predictable side effects resulting from this collection will take +place. `dnl' will return no output. The input following the matching +close parenthesis up to and including the next newline, on whatever +line containing it, will still be discarded. + + dnl(`args are ignored, but side effects occur', + define(`foo', `like this')) while this text is ignored: undefine(`foo') + error-->m4:stdin:1: Warning: excess arguments to builtin `dnl' ignored + See how `foo' was defined, foo? + =>See how foo was defined, like this? + + If the end of file is encountered without a newline character, a +warning is issued and dnl stops consuming input. + + m4wrap(`m4wrap(`2 hi + ')0 hi dnl 1 hi') + => + define(`hi', `HI') + => + ^D + error-->m4:stdin:1: Warning: end of file treated as newline + =>0 HI 2 HI + + +File: m4.info, Node: Changequote, Next: Changecom, Prev: Dnl, Up: Input Control + +8.2 Changing the quote characters +================================= + +The default quote delimiters can be changed with the builtin +`changequote': + + -- Builtin: changequote ([START = ``'], [END = `'']) + This sets START as the new begin-quote delimiter and END as the + new end-quote delimiter. If both arguments are missing, the + default quotes (``' and `'') are used. If START is void, then + quoting is disabled. Otherwise, if END is missing or void, the + default end-quote delimiter (`'') is used. The quote delimiters + can be of any length. + + The expansion of `changequote' is void. + + changequote(`[', `]') + => + define([foo], [Macro [foo].]) + => + foo + =>Macro foo. + + The quotation strings can safely contain eight-bit characters. If +no single character is appropriate, START and END can be of any length. +Other implementations cap the delimiter length to five characters, but +GNU has no inherent limit. + + changequote(`[[[', `]]]') + => + define([[[foo]]], [[[Macro [[[[[foo]]]]].]]]) + => + foo + =>Macro [[foo]]. + + Calling `changequote' with START as the empty string will +effectively disable the quoting mechanism, leaving no way to quote text. +However, using an empty string is not portable, as some other +implementations of `m4' revert to the default quoting, while others +preserve the prior non-empty delimiter. If START is not empty, then an +empty END will use the default end-quote delimiter of `'', as +otherwise, it would be impossible to end a quoted string. Again, this +is not portable, as some other `m4' implementations reuse START as the +end-quote delimiter, while others preserve the previous non-empty +value. Omitting both arguments restores the default begin-quote and +end-quote delimiters; fortunately this behavior is portable to all +implementations of `m4'. + + define(`foo', `Macro `FOO'.') + => + changequote(`', `') + => + foo + =>Macro `FOO'. + `foo' + =>`Macro `FOO'.' + changequote(`,) + => + foo + =>Macro FOO. + + There is no way in `m4' to quote a string containing an unmatched +begin-quote, except using `changequote' to change the current quotes. + + If the quotes should be changed from, say, `[' to `[[', temporary +quote characters have to be defined. To achieve this, two calls of +`changequote' must be made, one for the temporary quotes and one for +the new quotes. + + Macros are recognized in preference to the begin-quote string, so if +a prefix of START can be recognized as part of a potential macro name, +the quoting mechanism is effectively disabled. Unless you use +`changeword' (*note Changeword::), this means that START should not +begin with a letter, digit, or `_' (underscore). However, even though +quoted strings are not recognized, the quote characters can still be +discerned in macro expansion and in trace output. + + define(`echo', `$@') + => + define(`hi', `HI') + => + changequote(`q', `Q') + => + q hi Q hi + =>q HI Q HI + echo(hi) + =>qHIQ + changequote + => + changequote(`-', `EOF') + => + - hi EOF hi + => hi HI + changequote + => + changequote(`1', `2') + => + hi1hi2 + =>hi1hi2 + hi 1hi2 + =>HI hi + + Quotes are recognized in preference to argument collection. In +particular, if START is a single `(', then argument collection is +effectively disabled. For portability with other implementations, it +is a good idea to avoid `(', `,', and `)' as the first character in +START. + + define(`echo', `$#:$@:') + => + define(`hi', `HI') + => + changequote(`(',`)') + => + echo(hi) + =>0::hi + changequote + => + changequote(`((', `))') + => + echo(hi) + =>1:HI: + echo((hi)) + =>0::hi + changequote + => + changequote(`,', `)') + => + echo(hi,hi)bye) + =>1:HIhibye: + + However, if you are not worried about portability, using `(' and `)' +as quoting characters has an interesting property--you can use it to +compute a quoted string containing the expansion of any quoted text, as +long as the expansion results in both balanced quotes and balanced +parentheses. The trick is realizing `expand' uses `$1' unquoted, to +trigger its expansion using the normal quoting characters, but uses +extra parentheses to group unquoted commas that occur in the expansion +without consuming whitespace following those commas. Then `_expand' +uses `changequote' to convert the extra parentheses back into quoting +characters. Note that it takes two more `changequote' invocations to +restore the original quotes. Contrast the behavior on whitespace when +using `$*', via `quote', to attempt the same task. + + changequote(`[', `]')dnl + define([a], [1, (b)])dnl + define([b], [2])dnl + define([quote], [[$*]])dnl + define([expand], [_$0(($1))])dnl + define([_expand], + [changequote([(], [)])$1changequote`'changequote(`[', `]')])dnl + expand([a, a, [a, a], [[a, a]]]) + =>1, (2), 1, (2), a, a, [a, a] + quote(a, a, [a, a], [[a, a]]) + =>1,(2),1,(2),a, a,[a, a] + + If END is a prefix of START, the end-quote will be recognized in +preference to a nested begin-quote. In particular, changing the quotes +to have the same string for START and END disables nesting of quotes. +When quote nesting is disabled, it is impossible to double-quote +strings across macro expansions, so using the same string is not done +very often. + + define(`hi', `HI') + => + changequote(`""', `"') + => + ""hi"""hi" + =>hihi + ""hi" ""hi" + =>hi hi + ""hi"" "hi" + =>hi" "HI" + changequote + => + `hi`hi'hi' + =>hi`hi'hi + changequote(`"', `"') + => + "hi"hi"hi" + =>hiHIhi + + It is an error if the end of file occurs within a quoted string. + + `hello world' + =>hello world + `dangling quote + ^D + error-->m4:stdin:2: ERROR: end of file in string + + ifelse(`dangling quote + ^D + error-->m4:stdin:1: ERROR: end of file in string + + +File: m4.info, Node: Changecom, Next: Changeword, Prev: Changequote, Up: Input Control + +8.3 Changing the comment delimiters +=================================== + +The default comment delimiters can be changed with the builtin macro +`changecom': + + -- Builtin: changecom ([START], [END = `<NL>']) + This sets START as the new begin-comment delimiter and END as the + new end-comment delimiter. If both arguments are missing, or + START is void, then comments are disabled. Otherwise, if END is + missing or void, the default end-comment delimiter of newline is + used. The comment delimiters can be of any length. + + The expansion of `changecom' is void. + + define(`comment', `COMMENT') + => + # A normal comment + =># A normal comment + changecom(`/*', `*/') + => + # Not a comment anymore + =># Not a COMMENT anymore + But: /* this is a comment now */ while this is not a comment + =>But: /* this is a comment now */ while this is not a COMMENT + + Note how comments are copied to the output, much as if they were +quoted strings. If you want the text inside a comment expanded, quote +the begin-comment delimiter. + + Calling `changecom' without any arguments, or with START as the +empty string, will effectively disable the commenting mechanism. To +restore the original comment start of `#', you must explicitly ask for +it. If START is not empty, then an empty END will use the default +end-comment delimiter of newline, as otherwise, it would be impossible +to end a comment. However, this is not portable, as some other `m4' +implementations preserve the previous non-empty delimiters instead. + + define(`comment', `COMMENT') + => + changecom + => + # Not a comment anymore + =># Not a COMMENT anymore + changecom(`#', `') + => + # comment again + =># comment again + + The comment strings can safely contain eight-bit characters. If no +single character is appropriate, START and END can be of any length. +Other implementations cap the delimiter length to five characters, but +GNU has no inherent limit. + + Comments are recognized in preference to macros. However, this is +not compatible with other implementations, where macros and even quoting +takes precedence over comments, so it may change in a future release. +For portability, this means that START should not begin with a letter, +digit, or `_' (underscore), and that neither the start-quote nor the +start-comment string should be a prefix of the other. + + define(`hi', `HI') + => + define(`hi1hi2', `hello') + => + changecom(`q', `Q') + => + q hi Q hi + =>q hi Q HI + changecom(`1', `2') + => + hi1hi2 + =>hello + hi 1hi2 + =>HI 1hi2 + + Comments are recognized in preference to argument collection. In +particular, if START is a single `(', then argument collection is +effectively disabled. For portability with other implementations, it +is a good idea to avoid `(', `,', and `)' as the first character in +START. + + define(`echo', `$#:$*:$@:') + => + define(`hi', `HI') + => + changecom(`(',`)') + => + echo(hi) + =>0:::(hi) + changecom + => + changecom(`((', `))') + => + echo(hi) + =>1:HI:HI: + echo((hi)) + =>0:::((hi)) + changecom(`,', `)') + => + echo(hi,hi)bye) + =>1:HI,hi)bye:HI,hi)bye: + changecom + => + echo(hi,`,`'hi',hi) + =>3:HI,,HI,HI:HI,,`'hi,HI: + echo(hi,`,`'hi',hi`'changecom(`,,', `hi')) + =>3:HI,,`'hi,HI:HI,,`'hi,HI: + + It is an error if the end of file occurs within a comment. + + changecom(`/*', `*/') + => + /*dangling comment + ^D + error-->m4:stdin:2: ERROR: end of file in comment + + +File: m4.info, Node: Changeword, Next: M4wrap, Prev: Changecom, Up: Input Control + +8.4 Changing the lexical structure of words +=========================================== + + The macro `changeword' and all associated functionality is + experimental. It is only available if the `--enable-changeword' + option was given to `configure', at GNU `m4' installation time. + The functionality will go away in the future, to be replaced by + other new features that are more efficient at providing the same + capabilities. _Do not rely on it_. Please direct your comments + about it the same way you would do for bugs. + + A file being processed by `m4' is split into quoted strings, words +(potential macro names) and simple tokens (any other single character). +Initially a word is defined by the following regular expression: + + [_a-zA-Z][_a-zA-Z0-9]* + + Using `changeword', you can change this regular expression: + + -- Optional builtin: changeword (REGEX) + Changes the regular expression for recognizing macro names to be + REGEX. If REGEX is empty, use `[_a-zA-Z][_a-zA-Z0-9]*'. REGEX + must obey the constraint that every prefix of the desired final + pattern is also accepted by the regular expression. If REGEX + contains grouping parentheses, the macro invoked is the portion + that matched the first group, rather than the entire matching + string. + + The expansion of `changeword' is void. The macro `changeword' is + recognized only with parameters. + + Relaxing the lexical rules of `m4' might be useful (for example) if +you wanted to apply translations to a file of numbers: + + ifdef(`changeword', `', `errprint(` skipping: no changeword support + ')m4exit(`77')')dnl + changeword(`[_a-zA-Z0-9]+') + => + define(`1', `0')1 + =>0 + + Tightening the lexical rules is less useful, because it will +generally make some of the builtins unavailable. You could use it to +prevent accidental call of builtins, for example: + + ifdef(`changeword', `', `errprint(` skipping: no changeword support + ')m4exit(`77')')dnl + define(`_indir', defn(`indir')) + => + changeword(`_[_a-zA-Z0-9]*') + => + esyscmd(`foo') + =>esyscmd(foo) + _indir(`esyscmd', `echo hi') + =>hi + => + + Because `m4' constructs its words a character at a time, there is a +restriction on the regular expressions that may be passed to +`changeword'. This is that if your regular expression accepts `foo', +it must also accept `f' and `fo'. + + ifdef(`changeword', `', `errprint(` skipping: no changeword support + ')m4exit(`77')')dnl + define(`foo + ', `bar + ') + => + dnl This example wants to recognize changeword, dnl, and `foo\n'. + dnl First, we check that our regexp will match. + regexp(`changeword', `[cd][a-z]*\|foo[ + ]') + =>0 + regexp(`foo + ', `[cd][a-z]*\|foo[ + ]') + =>0 + regexp(`f', `[cd][a-z]*\|foo[ + ]') + =>-1 + foo + =>foo + changeword(`[cd][a-z]*\|foo[ + ]') + => + dnl Even though `foo\n' matches, we forgot to allow `f'. + foo + =>foo + changeword(`[cd][a-z]*\|fo*[ + ]?') + => + dnl Now we can call `foo\n'. + foo + =>bar + + `changeword' has another function. If the regular expression +supplied contains any grouped subexpressions, then text outside the +first of these is discarded before symbol lookup. So: + + ifdef(`changeword', `', `errprint(` skipping: no changeword support + ')m4exit(`77')')dnl + ifdef(`__unix__', , + `errprint(` skipping: syscmd does not have unix semantics + ')m4exit(`77')')dnl + changecom(`/*', `*/')dnl + define(`foo', `bar')dnl + changeword(`#\([_a-zA-Z0-9]*\)') + => + #esyscmd(`echo foo \#foo') + =>foo bar + => + + `m4' now requires a `#' mark at the beginning of every macro +invocation, so one can use `m4' to preprocess plain text without losing +various words like `divert'. + + In `m4', macro substitution is based on text, while in TeX, it is +based on tokens. `changeword' can throw this difference into relief. +For example, here is the same idea represented in TeX and `m4'. First, +the TeX version: + + \def\a{\message{Hello}} + \catcode`\@=0 + \catcode`\\=12 + @a + @bye + =>Hello + +Then, the `m4' version: + + ifdef(`changeword', `', `errprint(` skipping: no changeword support + ')m4exit(`77')')dnl + define(`a', `errprint(`Hello')')dnl + changeword(`@\([_a-zA-Z0-9]*\)') + => + @a + =>errprint(Hello) + + In the TeX example, the first line defines a macro `a' to print the +message `Hello'. The second line defines <@> to be usable instead of +<\> as an escape character. The third line defines <\> to be a normal +printing character, not an escape. The fourth line invokes the macro +`a'. So, when TeX is run on this file, it displays the message `Hello'. + + When the `m4' example is passed through `m4', it outputs +`errprint(Hello)'. The reason for this is that TeX does lexical +analysis of macro definition when the macro is _defined_. `m4' just +stores the text, postponing the lexical analysis until the macro is +_used_. + + You should note that using `changeword' will slow `m4' down by a +factor of about seven, once it is changed to something other than the +default regular expression. You can invoke `changeword' with the empty +string to restore the default word definition, and regain the parsing +speed. + + +File: m4.info, Node: M4wrap, Prev: Changeword, Up: Input Control + +8.5 Saving text until end of input +================================== + +It is possible to `save' some text until the end of the normal input has +been seen. Text can be saved, to be read again by `m4' when the normal +input has been exhausted. This feature is normally used to initiate +cleanup actions before normal exit, e.g., deleting temporary files. + + To save input text, use the builtin `m4wrap': + + -- Builtin: m4wrap (STRING, ...) + Stores STRING in a safe place, to be reread when end of input is + reached. As a GNU extension, additional arguments are + concatenated with a space to the STRING. + + The expansion of `m4wrap' is void. The macro `m4wrap' is + recognized only with parameters. + + define(`cleanup', `This is the `cleanup' action. + ') + => + m4wrap(`cleanup') + => + This is the first and last normal input line. + =>This is the first and last normal input line. + ^D + =>This is the cleanup action. + + The saved input is only reread when the end of normal input is seen, +and not if `m4exit' is used to exit `m4'. + + It is safe to call `m4wrap' from saved text, but then the order in +which the saved text is reread is undefined. If `m4wrap' is not used +recursively, the saved pieces of text are reread in the opposite order +in which they were saved (LIFO--last in, first out). However, this +behavior is likely to change in a future release, to match POSIX, so +you should not depend on this order. + + It is possible to emulate POSIX behavior even with older versions of +GNU M4 by including the file `m4-1.4.16/examples/wrapfifo.m4' from the +distribution: + + $ m4 -I examples + undivert(`wrapfifo.m4')dnl + =>dnl Redefine m4wrap to have FIFO semantics. + =>define(`_m4wrap_level', `0')dnl + =>define(`m4wrap', + =>`ifdef(`m4wrap'_m4wrap_level, + => `define(`m4wrap'_m4wrap_level, + => defn(`m4wrap'_m4wrap_level)`$1')', + => `builtin(`m4wrap', `define(`_m4wrap_level', + => incr(_m4wrap_level))dnl + =>m4wrap'_m4wrap_level)dnl + =>define(`m4wrap'_m4wrap_level, `$1')')')dnl + include(`wrapfifo.m4') + => + m4wrap(`a`'m4wrap(`c + ', `d')')m4wrap(`b') + => + ^D + =>abc + + It is likewise possible to emulate LIFO behavior without resorting to +the GNU M4 extension of `builtin', by including the file +`m4-1.4.16/examples/wraplifo.m4' from the distribution. +(Unfortunately, both examples shown here share some subtle bugs. See +if you can find and correct them; or *note Answers: Improved m4wrap.). + + $ m4 -I examples + undivert(`wraplifo.m4')dnl + =>dnl Redefine m4wrap to have LIFO semantics. + =>define(`_m4wrap_level', `0')dnl + =>define(`_m4wrap', defn(`m4wrap'))dnl + =>define(`m4wrap', + =>`ifdef(`m4wrap'_m4wrap_level, + => `define(`m4wrap'_m4wrap_level, + => `$1'defn(`m4wrap'_m4wrap_level))', + => `_m4wrap(`define(`_m4wrap_level', incr(_m4wrap_level))dnl + =>m4wrap'_m4wrap_level)dnl + =>define(`m4wrap'_m4wrap_level, `$1')')')dnl + include(`wraplifo.m4') + => + m4wrap(`a`'m4wrap(`c + ', `d')')m4wrap(`b') + => + ^D + =>bac + + Here is an example of implementing a factorial function using +`m4wrap': + + define(`f', `ifelse(`$1', `0', `Answer: 0!=1 + ', eval(`$1>1'), `0', `Answer: $2$1=eval(`$2$1') + ', `m4wrap(`f(decr(`$1'), `$2$1*')')')') + => + f(`10') + => + ^D + =>Answer: 10*9*8*7*6*5*4*3*2*1=3628800 + + Invocations of `m4wrap' at the same recursion level are concatenated +and rescanned as usual: + + define(`aa', `AA + ') + => + m4wrap(`a')m4wrap(`a') + => + ^D + =>AA + +however, the transition between recursion levels behaves like an end of +file condition between two input files. + + m4wrap(`m4wrap(`)')len(abc') + => + ^D + error-->m4:stdin:1: ERROR: end of file in argument list + + +File: m4.info, Node: File Inclusion, Next: Diversions, Prev: Input Control, Up: Top + +9 File inclusion +**************** + +`m4' allows you to include named files at any point in the input. + +* Menu: + +* Include:: Including named files +* Search Path:: Searching for include files + + +File: m4.info, Node: Include, Next: Search Path, Up: File Inclusion + +9.1 Including named files +========================= + +There are two builtin macros in `m4' for including files: + + -- Builtin: include (FILE) + -- Builtin: sinclude (FILE) + Both macros cause the file named FILE to be read by `m4'. When + the end of the file is reached, input is resumed from the previous + input file. + + The expansion of `include' and `sinclude' is therefore the + contents of FILE. + + If FILE does not exist, is a directory, or cannot otherwise be + read, the expansion is void, and `include' will fail with an error + while `sinclude' is silent. The empty string counts as a file + that does not exist. + + The macros `include' and `sinclude' are recognized only with + parameters. + + include(`none') + error-->m4:stdin:1: cannot open `none': No such file or directory + => + include() + error-->m4:stdin:2: cannot open `': No such file or directory + => + sinclude(`none') + => + sinclude() + => + + The rest of this section assumes that `m4' is invoked with the `-I' +option (*note Invoking m4: Preprocessor features.) pointing to the +`m4-1.4.16/examples' directory shipped as part of the GNU `m4' package. +The file `m4-1.4.16/examples/incl.m4' in the distribution contains the +lines: + + $ cat examples/incl.m4 + =>Include file start + =>foo + =>Include file end + + Normally file inclusion is used to insert the contents of a file +into the input stream. The contents of the file will be read by `m4' +and macro calls in the file will be expanded: + + $ m4 -I examples + define(`foo', `FOO') + => + include(`incl.m4') + =>Include file start + =>FOO + =>Include file end + => + + The fact that `include' and `sinclude' expand to the contents of the +file can be used to define macros that operate on entire files. Here +is an example, which defines `bar' to expand to the contents of +`incl.m4': + + $ m4 -I examples + define(`bar', include(`incl.m4')) + => + This is `bar': >>bar<< + =>This is bar: >>Include file start + =>foo + =>Include file end + =><< + + This use of `include' is not trivial, though, as files can contain +quotes, commas, and parentheses, which can interfere with the way the +`m4' parser works. GNU `m4' seamlessly concatenates the file contents +with the next character, even if the included file ended in the middle +of a comment, string, or macro call. These conditions are only treated +as end of file errors if specified as input files on the command line. + + In GNU `m4', an alternative method of reading files is using +`undivert' (*note Undivert::) on a named file. + + +File: m4.info, Node: Search Path, Prev: Include, Up: File Inclusion + +9.2 Searching for include files +=============================== + +GNU `m4' allows included files to be found in other directories than +the current working directory. + + If the `--prepend-include' or `-B' command-line option was provided +(*note Invoking m4: Preprocessor features.), those directories are +searched first, in reverse order that those options were listed on the +command line. Then `m4' looks in the current working directory. Next +comes the directories specified with the `--include' or `-I' option, in +the order found on the command line. Finally, if the `M4PATH' +environment variable is set, it is expected to contain a +colon-separated list of directories, which will be searched in order. + + If the automatic search for include-files causes trouble, the `p' +debug flag (*note Debug Levels::) can help isolate the problem. + + +File: m4.info, Node: Diversions, Next: Text handling, Prev: File Inclusion, Up: Top + +10 Diverting and undiverting output +*********************************** + +Diversions are a way of temporarily saving output. The output of `m4' +can at any time be diverted to a temporary file, and be reinserted into +the output stream, "undiverted", again at a later time. + + Numbered diversions are counted from 0 upwards, diversion number 0 +being the normal output stream. GNU `m4' tries to keep diversions in +memory. However, there is a limit to the overall memory usable by all +diversions taken together (512K, currently). When this maximum is +about to be exceeded, a temporary file is opened to receive the +contents of the biggest diversion still in memory, freeing this memory +for other diversions. When creating the temporary file, `m4' honors +the value of the environment variable `TMPDIR', and falls back to +`/tmp'. Thus, the amount of available disk space provides the only +real limit on the number and aggregate size of diversions. + + Diversions make it possible to generate output in a different order +than the input was read. It is possible to implement topological +sorting dependencies. For example, GNU Autoconf makes use of +diversions under the hood to ensure that the expansion of a prerequisite +macro appears in the output prior to the expansion of a dependent macro, +regardless of which order the two macros were invoked in the user's +input file. + +* Menu: + +* Divert:: Diverting output +* Undivert:: Undiverting output +* Divnum:: Diversion numbers +* Cleardivert:: Discarding diverted text + + +File: m4.info, Node: Divert, Next: Undivert, Up: Diversions + +10.1 Diverting output +===================== + +Output is diverted using `divert': + + -- Builtin: divert ([NUMBER = `0']) + The current diversion is changed to NUMBER. If NUMBER is left out + or empty, it is assumed to be zero. If NUMBER cannot be parsed, + the diversion is unchanged. + + The expansion of `divert' is void. + + When all the `m4' input will have been processed, all existing +diversions are automatically undiverted, in numerical order. + + divert(`1') + This text is diverted. + divert + => + This text is not diverted. + =>This text is not diverted. + ^D + => + =>This text is diverted. + + Several calls of `divert' with the same argument do not overwrite +the previous diverted text, but append to it. Diversions are printed +after any wrapped text is expanded. + + define(`text', `TEXT') + => + divert(`1')`diverted text.' + divert + => + m4wrap(`Wrapped text precedes ') + => + ^D + =>Wrapped TEXT precedes diverted text. + + If output is diverted to a negative diversion, it is simply +discarded. This can be used to suppress unwanted output. A common +example of unwanted output is the trailing newlines after macro +definitions. Here is a common programming idiom in `m4' for avoiding +them. + + divert(`-1') + define(`foo', `Macro `foo'.') + define(`bar', `Macro `bar'.') + divert + => + + Traditional implementations only supported ten diversions. But as a +GNU extension, diversion numbers can be as large as positive integers +will allow, rather than treating a multi-digit diversion number as a +request to discard text. + + divert(eval(`1<<28'))world + divert(`2')hello + ^D + =>hello + =>world + + Note that `divert' is an English word, but also an active macro +without arguments. When processing plain text, the word might appear in +normal text and be unintentionally swallowed as a macro invocation. One +way to avoid this is to use the `-P' option to rename all builtins +(*note Invoking m4: Operation modes.). Another is to write a wrapper +that requires a parameter to be recognized. + + We decided to divert the stream for irrigation. + =>We decided to the stream for irrigation. + define(`divert', `ifelse(`$#', `0', ``$0'', `builtin(`$0', $@)')') + => + divert(`-1') + Ignored text. + divert(`0') + => + We decided to divert the stream for irrigation. + =>We decided to divert the stream for irrigation. + + +File: m4.info, Node: Undivert, Next: Divnum, Prev: Divert, Up: Diversions + +10.2 Undiverting output +======================= + +Diverted text can be undiverted explicitly using the builtin `undivert': + + -- Builtin: undivert ([DIVERSIONS...]) + Undiverts the numeric DIVERSIONS given by the arguments, in the + order given. If no arguments are supplied, all diversions are + undiverted, in numerical order. + + As a GNU extension, DIVERSIONS may contain non-numeric strings, + which are treated as the names of files to copy into the output + without expansion. A warning is issued if a file could not be + opened. + + The expansion of `undivert' is void. + + divert(`1') + This text is diverted. + divert + => + This text is not diverted. + =>This text is not diverted. + undivert(`1') + => + =>This text is diverted. + => + + Notice the last two blank lines. One of them comes from the newline +following `undivert', the other from the newline that followed the +`divert'! A diversion often starts with a blank line like this. + + When diverted text is undiverted, it is _not_ reread by `m4', but +rather copied directly to the current output, and it is therefore not +an error to undivert into a diversion. Undiverting the empty string is +the same as specifying diversion 0; in either case nothing happens +since the output has already been flushed. + + divert(`1')diverted text + divert + => + undivert() + => + undivert(`0') + => + undivert + =>diverted text + => + divert(`1')more + divert(`2')undivert(`1')diverted text`'divert + => + undivert(`1') + => + undivert(`2') + =>more + =>diverted text + + When a diversion has been undiverted, the diverted text is discarded, +and it is not possible to bring back diverted text more than once. + + divert(`1') + This text is diverted first. + divert(`0')undivert(`1')dnl + => + =>This text is diverted first. + undivert(`1') + => + divert(`1') + This text is also diverted but not appended. + divert(`0')undivert(`1')dnl + => + =>This text is also diverted but not appended. + + Attempts to undivert the current diversion are silently ignored. +Thus, when the current diversion is not 0, the current diversion does +not get rearranged among the other diversions. + + divert(`1')one + divert(`2')two + divert(`3')three + divert(`2')undivert`'dnl + divert`'undivert`'dnl + =>two + =>one + =>three + + GNU `m4' allows named files to be undiverted. Given a non-numeric +argument, the contents of the file named will be copied, uninterpreted, +to the current output. This complements the builtin `include' (*note +Include::). To illustrate the difference, assume the file `foo' +contains: + + $ cat foo + bar + +then + + define(`bar', `BAR') + => + undivert(`foo') + =>bar + => + include(`foo') + =>BAR + => + + If the file is not found (or cannot be read), an error message is +issued, and the expansion is void. It is possible to intermix files +and diversion numbers. + + divert(`1')diversion one + divert(`2')undivert(`foo')dnl + divert(`3')diversion three + divert`'dnl + undivert(`1', `2', `foo', `3')dnl + =>diversion one + =>bar + =>bar + =>diversion three + + +File: m4.info, Node: Divnum, Next: Cleardivert, Prev: Undivert, Up: Diversions + +10.3 Diversion numbers +====================== + +The current diversion is tracked by the builtin `divnum': + + -- Builtin: divnum + Expands to the number of the current diversion. + + Initial divnum + =>Initial 0 + divert(`1') + Diversion one: divnum + divert(`2') + Diversion two: divnum + ^D + => + =>Diversion one: 1 + => + =>Diversion two: 2 + + +File: m4.info, Node: Cleardivert, Prev: Divnum, Up: Diversions + +10.4 Discarding diverted text +============================= + +Often it is not known, when output is diverted, whether the diverted +text is actually needed. Since all non-empty diversion are brought back +on the main output stream when the end of input is seen, a method of +discarding a diversion is needed. If all diversions should be +discarded, the easiest is to end the input to `m4' with `divert(`-1')' +followed by an explicit `undivert': + + divert(`1') + Diversion one: divnum + divert(`2') + Diversion two: divnum + divert(`-1') + undivert + ^D + +No output is produced at all. + + Clearing selected diversions can be done with the following macro: + + -- Composite: cleardivert ([DIVERSIONS...]) + Discard the contents of each of the listed numeric DIVERSIONS. + + define(`cleardivert', + `pushdef(`_n', divnum)divert(`-1')undivert($@)divert(_n)popdef(`_n')') + => + + It is called just like `undivert', but the effect is to clear the +diversions, given by the arguments. (This macro has a nasty bug! You +should try to see if you can find it and correct it; or *note Answers: +Improved cleardivert.). + + +File: m4.info, Node: Text handling, Next: Arithmetic, Prev: Diversions, Up: Top + +11 Macros for text handling +*************************** + +There are a number of builtins in `m4' for manipulating text in various +ways, extracting substrings, searching, substituting, and so on. + +* Menu: + +* Len:: Calculating length of strings +* Index macro:: Searching for substrings +* Regexp:: Searching for regular expressions +* Substr:: Extracting substrings +* Translit:: Translating characters +* Patsubst:: Substituting text by regular expression +* Format:: Formatting strings (printf-like) + + +File: m4.info, Node: Len, Next: Index macro, Up: Text handling + +11.1 Calculating length of strings +================================== + +The length of a string can be calculated by `len': + + -- Builtin: len (STRING) + Expands to the length of STRING, as a decimal number. + + The macro `len' is recognized only with parameters. + + len() + =>0 + len(`abcdef') + =>6 + + +File: m4.info, Node: Index macro, Next: Regexp, Prev: Len, Up: Text handling + +11.2 Searching for substrings +============================= + +Searching for substrings is done with `index': + + -- Builtin: index (STRING, SUBSTRING) + Expands to the index of the first occurrence of SUBSTRING in + STRING. The first character in STRING has index 0. If SUBSTRING + does not occur in STRING, `index' expands to `-1'. + + The macro `index' is recognized only with parameters. + + index(`gnus, gnats, and armadillos', `nat') + =>7 + index(`gnus, gnats, and armadillos', `dag') + =>-1 + + Omitting SUBSTRING evokes a warning, but still produces output; +contrast this with an empty SUBSTRING. + + index(`abc') + error-->m4:stdin:1: Warning: too few arguments to builtin `index' + =>0 + index(`abc', `') + =>0 + index(`abc', `b') + =>1 + + +File: m4.info, Node: Regexp, Next: Substr, Prev: Index macro, Up: Text handling + +11.3 Searching for regular expressions +====================================== + +Searching for regular expressions is done with the builtin `regexp': + + -- Builtin: regexp (STRING, REGEXP, [REPLACEMENT]) + Searches for REGEXP in STRING. The syntax for regular expressions + is the same as in GNU Emacs, which is similar to BRE, Basic + Regular Expressions in POSIX. *Note Syntax of Regular + Expressions: (emacs)Regexps. Support for ERE, Extended Regular + Expressions is not available, but will be added in GNU M4 2.0. + + If REPLACEMENT is omitted, `regexp' expands to the index of the + first match of REGEXP in STRING. If REGEXP does not match + anywhere in STRING, it expands to -1. + + If REPLACEMENT is supplied, and there was a match, `regexp' + changes the expansion to this argument, with `\N' substituted by + the text matched by the Nth parenthesized sub-expression of + REGEXP, up to nine sub-expressions. The escape `\&' is replaced + by the text of the entire regular expression matched. For all + other characters, `\' treats the next character literally. A + warning is issued if there were fewer sub-expressions than the + `\N' requested, or if there is a trailing `\'. If there was no + match, `regexp' expands to the empty string. + + The macro `regexp' is recognized only with parameters. + + regexp(`GNUs not Unix', `\<[a-z]\w+') + =>5 + regexp(`GNUs not Unix', `\<Q\w*') + =>-1 + regexp(`GNUs not Unix', `\w\(\w+\)$', `*** \& *** \1 ***') + =>*** Unix *** nix *** + regexp(`GNUs not Unix', `\<Q\w*', `*** \& *** \1 ***') + => + + Here are some more examples on the handling of backslash: + + regexp(`abc', `\(b\)', `\\\10\a') + =>\b0a + regexp(`abc', `b', `\1\') + error-->m4:stdin:2: Warning: sub-expression 1 not present + error-->m4:stdin:2: Warning: trailing \ ignored in replacement + => + regexp(`abc', `\(\(d\)?\)\(c\)', `\1\2\3\4\5\6') + error-->m4:stdin:3: Warning: sub-expression 4 not present + error-->m4:stdin:3: Warning: sub-expression 5 not present + error-->m4:stdin:3: Warning: sub-expression 6 not present + =>c + + Omitting REGEXP evokes a warning, but still produces output; +contrast this with an empty REGEXP argument. + + regexp(`abc') + error-->m4:stdin:1: Warning: too few arguments to builtin `regexp' + =>0 + regexp(`abc', `') + =>0 + regexp(`abc', `', `\\def') + =>\def + + +File: m4.info, Node: Substr, Next: Translit, Prev: Regexp, Up: Text handling + +11.4 Extracting substrings +========================== + +Substrings are extracted with `substr': + + -- Builtin: substr (STRING, FROM, [LENGTH]) + Expands to the substring of STRING, which starts at index FROM, + and extends for LENGTH characters, or to the end of STRING, if + LENGTH is omitted. The starting index of a string is always 0. + The expansion is empty if there is an error parsing FROM or + LENGTH, if FROM is beyond the end of STRING, or if LENGTH is + negative. + + The macro `substr' is recognized only with parameters. + + substr(`gnus, gnats, and armadillos', `6') + =>gnats, and armadillos + substr(`gnus, gnats, and armadillos', `6', `5') + =>gnats + + Omitting FROM evokes a warning, but still produces output. + + substr(`abc') + error-->m4:stdin:1: Warning: too few arguments to builtin `substr' + =>abc + substr(`abc',) + error-->m4:stdin:2: empty string treated as 0 in builtin `substr' + =>abc + + +File: m4.info, Node: Translit, Next: Patsubst, Prev: Substr, Up: Text handling + +11.5 Translating characters +=========================== + +Character translation is done with `translit': + + -- Builtin: translit (STRING, CHARS, [REPLACEMENT]) + Expands to STRING, with each character that occurs in CHARS + translated into the character from REPLACEMENT with the same index. + + If REPLACEMENT is shorter than CHARS, the excess characters of + CHARS are deleted from the expansion; if CHARS is shorter, the + excess characters in REPLACEMENT are silently ignored. If + REPLACEMENT is omitted, all characters in STRING that are present + in CHARS are deleted from the expansion. If a character appears + more than once in CHARS, only the first instance is used in making + the translation. Only a single translation pass is made, even if + characters in REPLACEMENT also appear in CHARS. + + As a GNU extension, both CHARS and REPLACEMENT can contain + character-ranges, e.g., `a-z' (meaning all lowercase letters) or + `0-9' (meaning all digits). To include a dash `-' in CHARS or + REPLACEMENT, place it first or last in the entire string, or as + the last character of a range. Back-to-back ranges can share a + common endpoint. It is not an error for the last character in the + range to be `larger' than the first. In that case, the range runs + backwards, i.e., `9-0' means the string `9876543210'. The + expansion of a range is dependent on the underlying encoding of + characters, so using ranges is not always portable between + machines. + + The macro `translit' is recognized only with parameters. + + translit(`GNUs not Unix', `A-Z') + =>s not nix + translit(`GNUs not Unix', `a-z', `A-Z') + =>GNUS NOT UNIX + translit(`GNUs not Unix', `A-Z', `z-a') + =>tmfs not fnix + translit(`+,-12345', `+--1-5', `<;>a-c-a') + =><;>abcba + translit(`abcdef', `aabdef', `bcged') + =>bgced + + In the ASCII encoding, the first example deletes all uppercase +letters, the second converts lowercase to uppercase, and the third +`mirrors' all uppercase letters, while converting them to lowercase. +The two first cases are by far the most common, even though they are not +portable to EBCDIC or other encodings. The fourth example shows a +range ending in `-', as well as back-to-back ranges. The final example +shows that `a' is mapped to `b', not `c'; the resulting `b' is not +further remapped to `g'; the `d' and `e' are swapped, and the `f' is +discarded. + + Omitting CHARS evokes a warning, but still produces output. + + translit(`abc') + error-->m4:stdin:1: Warning: too few arguments to builtin `translit' + =>abc + + +File: m4.info, Node: Patsubst, Next: Format, Prev: Translit, Up: Text handling + +11.6 Substituting text by regular expression +============================================ + +Global substitution in a string is done by `patsubst': + + -- Builtin: patsubst (STRING, REGEXP, [REPLACEMENT]) + Searches STRING for matches of REGEXP, and substitutes REPLACEMENT + for each match. The syntax for regular expressions is the same as + in GNU Emacs (*note Regexp::). + + The parts of STRING that are not covered by any match of REGEXP + are copied to the expansion. Whenever a match is found, the + search proceeds from the end of the match, so a character from + STRING will never be substituted twice. If REGEXP matches a + string of zero length, the start position for the search is + incremented, to avoid infinite loops. + + When a replacement is to be made, REPLACEMENT is inserted into the + expansion, with `\N' substituted by the text matched by the Nth + parenthesized sub-expression of PATSUBST, for up to nine + sub-expressions. The escape `\&' is replaced by the text of the + entire regular expression matched. For all other characters, `\' + treats the next character literally. A warning is issued if there + were fewer sub-expressions than the `\N' requested, or if there is + a trailing `\'. + + The REPLACEMENT argument can be omitted, in which case the text + matched by REGEXP is deleted. + + The macro `patsubst' is recognized only with parameters. + + patsubst(`GNUs not Unix', `^', `OBS: ') + =>OBS: GNUs not Unix + patsubst(`GNUs not Unix', `\<', `OBS: ') + =>OBS: GNUs OBS: not OBS: Unix + patsubst(`GNUs not Unix', `\w*', `(\&)') + =>(GNUs)() (not)() (Unix)() + patsubst(`GNUs not Unix', `\w+', `(\&)') + =>(GNUs) (not) (Unix) + patsubst(`GNUs not Unix', `[A-Z][a-z]+') + =>GN not + patsubst(`GNUs not Unix', `not', `NOT\') + error-->m4:stdin:6: Warning: trailing \ ignored in replacement + =>GNUs NOT Unix + + Here is a slightly more realistic example, which capitalizes +individual words or whole sentences, by substituting calls of the macros +`upcase' and `downcase' into the strings. + + -- Composite: upcase (TEXT) + -- Composite: downcase (TEXT) + -- Composite: capitalize (TEXT) + Expand to TEXT, but with capitalization changed: `upcase' changes + all letters to upper case, `downcase' changes all letters to lower + case, and `capitalize' changes the first character of each word to + upper case and the remaining characters to lower case. + + First, an example of their usage, using implementations distributed +in `m4-1.4.16/examples/capitalize.m4'. + + $ m4 -I examples + include(`capitalize.m4') + => + upcase(`GNUs not Unix') + =>GNUS NOT UNIX + downcase(`GNUs not Unix') + =>gnus not unix + capitalize(`GNUs not Unix') + =>Gnus Not Unix + + Now for the implementation. There is a helper macro `_capitalize' +which puts only its first word in mixed case. Then `capitalize' merely +parses out the words, and replaces them with an invocation of +`_capitalize'. (As presented here, the `capitalize' macro has some +subtle flaws. You should try to see if you can find and correct them; +or *note Answers: Improved capitalize.). + + $ m4 -I examples + undivert(`capitalize.m4')dnl + =>divert(`-1') + =># upcase(text) + =># downcase(text) + =># capitalize(text) + =># change case of text, simple version + =>define(`upcase', `translit(`$*', `a-z', `A-Z')') + =>define(`downcase', `translit(`$*', `A-Z', `a-z')') + =>define(`_capitalize', + => `regexp(`$1', `^\(\w\)\(\w*\)', + => `upcase(`\1')`'downcase(`\2')')') + =>define(`capitalize', `patsubst(`$1', `\w+', `_$0(`\&')')') + =>divert`'dnl + + While `regexp' replaces the whole input with the replacement as soon +as there is a match, `patsubst' replaces each _occurrence_ of a match +and preserves non-matching pieces: + + define(`patreg', + `patsubst($@) + regexp($@)')dnl + patreg(`bar foo baz Foo', `foo\|Foo', `FOO') + =>bar FOO baz FOO + =>FOO + patreg(`aba abb 121', `\(.\)\(.\)\1', `\2\1\2') + =>bab abb 212 + =>bab + + Omitting REGEXP evokes a warning, but still produces output; +contrast this with an empty REGEXP argument. + + patsubst(`abc') + error-->m4:stdin:1: Warning: too few arguments to builtin `patsubst' + =>abc + patsubst(`abc', `') + =>abc + patsubst(`abc', `', `\\-') + =>\-a\-b\-c\- + + +File: m4.info, Node: Format, Prev: Patsubst, Up: Text handling + +11.7 Formatting strings (printf-like) +===================================== + +Formatted output can be made with `format': + + -- Builtin: format (FORMAT-STRING, ...) + Works much like the C function `printf'. The first argument + FORMAT-STRING can contain `%' specifications which are satisfied + by additional arguments, and the expansion of `format' is the + formatted string. + + The macro `format' is recognized only with parameters. + + Its use is best described by a few examples: + + define(`foo', `The brown fox jumped over the lazy dog') + => + format(`The string "%s" uses %d characters', foo, len(foo)) + =>The string "The brown fox jumped over the lazy dog" uses 38 characters + format(`%*.*d', `-1', `-1', `1') + =>1 + format(`%.0f', `56789.9876') + =>56790 + len(format(`%-*X', `5000', `1')) + =>5000 + ifelse(format(`%010F', `infinity'), ` INF', `success', + format(`%010F', `infinity'), ` INFINITY', `success', + format(`%010F', `infinity')) + =>success + ifelse(format(`%.1A', `1.999'), `0X1.0P+1', `success', + format(`%.1A', `1.999'), `0X2.0P+0', `success', + format(`%.1A', `1.999')) + =>success + format(`%g', `0xa.P+1') + =>20 + + Using the `forloop' macro defined earlier (*note Forloop::), this +example shows how `format' can be used to produce tabular output. + + $ m4 -I examples + include(`forloop.m4') + => + forloop(`i', `1', `10', `format(`%6d squared is %10d + ', i, eval(i**2))') + => 1 squared is 1 + => 2 squared is 4 + => 3 squared is 9 + => 4 squared is 16 + => 5 squared is 25 + => 6 squared is 36 + => 7 squared is 49 + => 8 squared is 64 + => 9 squared is 81 + => 10 squared is 100 + => + + The builtin `format' is modeled after the ANSI C `printf' function, +and supports these `%' specifiers: `c', `s', `d', `o', `x', `X', `u', +`a', `A', `e', `E', `f', `F', `g', `G', and `%'; it supports field +widths and precisions, and the flags `+', `-', ` ', `0', `#', and `''. +For integer specifiers, the width modifiers `hh', `h', and `l' are +recognized, and for floating point specifiers, the width modifier `l' +is recognized. Items not yet supported include positional arguments, +the `n', `p', `S', and `C' specifiers, the `z', `t', `j', `L' and `ll' +modifiers, and any platform extensions available in the native +`printf'. For more details on the functioning of `printf', see the C +Library Manual, or the POSIX specification (for example, `%a' is +supported even on platforms that haven't yet implemented C99 +hexadecimal floating point output natively). + + Unrecognized specifiers result in a warning. It is anticipated that +a future release of GNU `m4' will support more specifiers, and give +better warnings when various problems such as overflow are encountered. +Likewise, escape sequences are not yet recognized. + + format(`%p', `0') + error-->m4:stdin:1: Warning: unrecognized specifier in `%p' + => + + +File: m4.info, Node: Arithmetic, Next: Shell commands, Prev: Text handling, Up: Top + +12 Macros for doing arithmetic +****************************** + +Integer arithmetic is included in `m4', with a C-like syntax. As +convenient shorthands, there are builtins for simple increment and +decrement operations. + +* Menu: + +* Incr:: Decrement and increment operators +* Eval:: Evaluating integer expressions + + +File: m4.info, Node: Incr, Next: Eval, Up: Arithmetic + +12.1 Decrement and increment operators +====================================== + +Increment and decrement of integers are supported using the builtins +`incr' and `decr': + + -- Builtin: incr (NUMBER) + -- Builtin: decr (NUMBER) + Expand to the numerical value of NUMBER, incremented or + decremented, respectively, by one. Except for the empty string, + the expansion is empty if NUMBER could not be parsed. + + The macros `incr' and `decr' are recognized only with parameters. + + incr(`4') + =>5 + decr(`7') + =>6 + incr() + error-->m4:stdin:3: empty string treated as 0 in builtin `incr' + =>1 + decr() + error-->m4:stdin:4: empty string treated as 0 in builtin `decr' + =>-1 + + +File: m4.info, Node: Eval, Prev: Incr, Up: Arithmetic + +12.2 Evaluating integer expressions +=================================== + +Integer expressions are evaluated with `eval': + + -- Builtin: eval (EXPRESSION, [RADIX = `10'], [WIDTH]) + Expands to the value of EXPRESSION. The expansion is empty if a + problem is encountered while parsing the arguments. If specified, + RADIX and WIDTH control the format of the output. + + Calculations are done with 32-bit signed numbers. Overflow + silently results in wraparound. A warning is issued if division + by zero is attempted, or if EXPRESSION could not be parsed. + + Expressions can contain the following operators, listed in order of + decreasing precedence. + + `()' + Parentheses + + `+ - ~ !' + Unary plus and minus, and bitwise and logical negation + + `**' + Exponentiation + + `* / %' + Multiplication, division, and modulo + + `+ -' + Addition and subtraction + + `<< >>' + Shift left or right + + `> >= < <=' + Relational operators + + `== !=' + Equality operators + + `&' + Bitwise and + + `^' + Bitwise exclusive-or + + `|' + Bitwise or + + `&&' + Logical and + + `||' + Logical or + + The macro `eval' is recognized only with parameters. + + All binary operators, except exponentiation, are left associative. C +operators that perform variable assignment, such as `+=' or `--', are +not implemented, since `eval' only operates on constants, not +variables. Attempting to use them results in an error. However, since +traditional implementations treated `=' as an undocumented alias for +`==' as opposed to an assignment operator, this usage is supported as a +special case. Be aware that a future version of GNU M4 may support +assignment semantics as an extension when POSIX mode is not requested, +and that using `=' to check equality is not portable. + + eval(`2 = 2') + error-->m4:stdin:1: Warning: recommend ==, not =, for equality operator + =>1 + eval(`++0') + error-->m4:stdin:2: invalid operator in eval: ++0 + => + eval(`0 |= 1') + error-->m4:stdin:3: invalid operator in eval: 0 |= 1 + => + + Note that some older `m4' implementations use `^' as an alternate +operator for the exponentiation, although POSIX requires the C behavior +of bitwise exclusive-or. The precedence of the negation operators, `~' +and `!', was traditionally lower than equality. The unary operators +could not be used reliably more than once on the same term without +intervening parentheses. The traditional precedence of the equality +operators `==' and `!=' was identical instead of lower than the +relational operators such as `<', even through GNU M4 1.4.8. Starting +with version 1.4.9, GNU M4 correctly follows POSIX precedence rules. +M4 scripts designed to be portable between releases must be aware that +parentheses may be required to enforce C precedence rules. Likewise, +division by zero, even in the unused branch of a short-circuiting +operator, is not always well-defined in other implementations. + + Following are some examples where the current version of M4 follows C +precedence rules, but where older versions and some other +implementations of `m4' require explicit parentheses to get the correct +result: + + eval(`1 == 2 > 0') + =>1 + eval(`(1 == 2) > 0') + =>0 + eval(`! 0 * 2') + =>2 + eval(`! (0 * 2)') + =>1 + eval(`1 | 1 ^ 1') + =>1 + eval(`(1 | 1) ^ 1') + =>0 + eval(`+ + - ~ ! ~ 0') + =>1 + eval(`2 || 1 / 0') + =>1 + eval(`0 || 1 / 0') + error-->m4:stdin:9: divide by zero in eval: 0 || 1 / 0 + => + eval(`0 && 1 % 0') + =>0 + eval(`2 && 1 % 0') + error-->m4:stdin:11: modulo by zero in eval: 2 && 1 % 0 + => + + As a GNU extension, the operator `**' performs integral +exponentiation. The operator is right-associative, and if evaluated, +the exponent must be non-negative, and at least one of the arguments +must be non-zero, or a warning is issued. + + eval(`2 ** 3 ** 2') + =>512 + eval(`(2 ** 3) ** 2') + =>64 + eval(`0 ** 1') + =>0 + eval(`2 ** 0') + =>1 + eval(`0 ** 0') + => + error-->m4:stdin:5: divide by zero in eval: 0 ** 0 + eval(`4 ** -2') + error-->m4:stdin:6: negative exponent in eval: 4 ** -2 + => + + Within EXPRESSION, (but not RADIX or WIDTH), numbers without a +special prefix are decimal. A simple `0' prefix introduces an octal +number. `0x' introduces a hexadecimal number. As GNU extensions, `0b' +introduces a binary number. `0r' introduces a number expressed in any +radix between 1 and 36: the prefix should be immediately followed by +the decimal expression of the radix, a colon, then the digits making +the number. For radix 1, leading zeros are ignored, and all remaining +digits must be `1'; for all other radices, the digits are `0', `1', `2', +.... Beyond `9', the digits are `a', `b' ... up to `z'. Lower and +upper case letters can be used interchangeably in numbers prefixes and +as number digits. + + Parentheses may be used to group subexpressions whenever needed. +For the relational operators, a true relation returns `1', and a false +relation return `0'. + + Here are a few examples of use of `eval'. + + eval(`-3 * 5') + =>-15 + eval(`-99 / 10') + =>-9 + eval(`-99 % 10') + =>-9 + eval(`99 % -10') + =>9 + eval(index(`Hello world', `llo') >= 0) + =>1 + eval(`0r1:0111 + 0b100 + 0r3:12') + =>12 + define(`square', `eval(`($1) ** 2')') + => + square(`9') + =>81 + square(square(`5')` + 1') + =>676 + define(`foo', `666') + => + eval(`foo / 6') + error-->m4:stdin:11: bad expression in eval: foo / 6 + => + eval(foo / 6) + =>111 + + As the last two lines show, `eval' does not handle macro names, even +if they expand to a valid expression (or part of a valid expression). +Therefore all macros must be expanded before they are passed to `eval'. + + Some calculations are not portable to other implementations, since +they have undefined semantics in C, but GNU `m4' has well-defined +behavior on overflow. When shifting, an out-of-range shift amount is +implicitly brought into the range of 32-bit signed integers using an +implicit bit-wise and with 0x1f). + + define(`max_int', eval(`0x7fffffff')) + => + define(`min_int', incr(max_int)) + => + eval(min_int` < 0') + =>1 + eval(max_int` > 0') + =>1 + ifelse(eval(min_int` / -1'), min_int, `overflow occurred') + =>overflow occurred + min_int + =>-2147483648 + eval(`0x80000000 % -1') + =>0 + eval(`-4 >> 1') + =>-2 + eval(`-4 >> 33') + =>-2 + + If RADIX is specified, it specifies the radix to be used in the +expansion. The default radix is 10; this is also the case if RADIX is +the empty string. A warning results if the radix is outside the range +of 1 through 36, inclusive. The result of `eval' is always taken to be +signed. No radix prefix is output, and for radices greater than 10, +the digits are lower case. The WIDTH argument specifies the minimum +output width, excluding any negative sign. The result is zero-padded +to extend the expansion to the requested width. A warning results if +the width is negative. If RADIX or WIDTH is out of bounds, the +expansion of `eval' is empty. + + eval(`666', `10') + =>666 + eval(`666', `11') + =>556 + eval(`666', `6') + =>3030 + eval(`666', `6', `10') + =>0000003030 + eval(`-666', `6', `10') + =>-0000003030 + eval(`10', `', `0') + =>10 + `0r1:'eval(`10', `1', `11') + =>0r1:01111111111 + eval(`10', `16') + =>a + eval(`1', `37') + error-->m4:stdin:9: radix 37 in builtin `eval' out of range + => + eval(`1', , `-1') + error-->m4:stdin:10: negative width to builtin `eval' + => + eval() + error-->m4:stdin:11: empty string treated as 0 in builtin `eval' + =>0 + + +File: m4.info, Node: Shell commands, Next: Miscellaneous, Prev: Arithmetic, Up: Top + +13 Macros for running shell commands +************************************ + +There are a few builtin macros in `m4' that allow you to run shell +commands from within `m4'. + + Note that the definition of a valid shell command is system +dependent. On UNIX systems, this is the typical `/bin/sh'. But on +other systems, such as native Windows, the shell has a different syntax +of commands that it understands. Some examples in this chapter assume +`/bin/sh', and also demonstrate how to quit early with a known exit +value if this is not the case. + +* Menu: + +* Platform macros:: Determining the platform +* Syscmd:: Executing simple commands +* Esyscmd:: Reading the output of commands +* Sysval:: Exit status +* Mkstemp:: Making temporary files + + +File: m4.info, Node: Platform macros, Next: Syscmd, Up: Shell commands + +13.1 Determining the platform +============================= + +Sometimes it is desirable for an input file to know which platform `m4' +is running on. GNU `m4' provides several macros that are predefined to +expand to the empty string; checking for their existence will confirm +platform details. + + -- Optional builtin: __gnu__ + -- Optional builtin: __os2__ + -- Optional builtin: os2 + -- Optional builtin: __unix__ + -- Optional builtin: unix + -- Optional builtin: __windows__ + -- Optional builtin: windows + Each of these macros is conditionally defined as needed to + describe the environment of `m4'. If defined, each macro expands + to the empty string. For now, these macros silently ignore all + arguments, but in a future release of M4, they might warn if + arguments are present. + + When GNU extensions are in effect (that is, when you did not use the +`-G' option, *note Invoking m4: Limits control.), GNU `m4' will define +the macro `__gnu__' to expand to the empty string. + + $ m4 + __gnu__ + => + __gnu__(`ignored') + => + Extensions are ifdef(`__gnu__', `active', `inactive') + =>Extensions are active + + $ m4 -G + __gnu__ + =>__gnu__ + __gnu__(`ignored') + =>__gnu__(ignored) + Extensions are ifdef(`__gnu__', `active', `inactive') + =>Extensions are inactive + + On UNIX systems, GNU `m4' will define `__unix__' by default, or +`unix' when the `-G' option is specified. + + On native Windows systems, GNU `m4' will define `__windows__' by +default, or `windows' when the `-G' option is specified. + + On OS/2 systems, GNU `m4' will define `__os2__' by default, or `os2' +when the `-G' option is specified. + + If GNU `m4' does not provide a platform macro for your system, +please report that as a bug. + + define(`provided', `0') + => + ifdef(`__unix__', `define(`provided', incr(provided))') + => + ifdef(`__windows__', `define(`provided', incr(provided))') + => + ifdef(`__os2__', `define(`provided', incr(provided))') + => + provided + =>1 + + +File: m4.info, Node: Syscmd, Next: Esyscmd, Prev: Platform macros, Up: Shell commands + +13.2 Executing simple commands +============================== + +Any shell command can be executed, using `syscmd': + + -- Builtin: syscmd (SHELL-COMMAND) + Executes SHELL-COMMAND as a shell command. + + The expansion of `syscmd' is void, _not_ the output from + SHELL-COMMAND! Output or error messages from SHELL-COMMAND are + not read by `m4'. *Note Esyscmd::, if you need to process the + command output. + + Prior to executing the command, `m4' flushes its buffers. The + default standard input, output and error of SHELL-COMMAND are the + same as those of `m4'. + + By default, the SHELL-COMMAND will be used as the argument to the + `-c' option of the `/bin/sh' shell (or the version of `sh' + specified by `command -p getconf PATH', if your system supports + that). If you prefer a different shell, the `configure' script + can be given the option `--with-syscmd-shell=LOCATION' to set the + location of an alternative shell at GNU `m4' installation; the + alternative shell must still support `-c'. + + The macro `syscmd' is recognized only with parameters. + + define(`foo', `FOO') + => + syscmd(`echo foo') + =>foo + => + + Note how the expansion of `syscmd' keeps the trailing newline of the +command, as well as using the newline that appeared after the macro. + + The following is an example of SHELL-COMMAND using the same standard +input as `m4': + + $ echo "m4wrap(\`syscmd(\`cat')')" | m4 + => + + It tells `m4' to read all of its input before executing the wrapped +text, then hand a valid (albeit emptied) pipe as standard input for the +`cat' subcommand. Therefore, you should be careful when using standard +input (either by specifying no files, or by passing `-' as a file name +on the command line, *note Invoking m4: Command line files.), and also +invoking subcommands via `syscmd' or `esyscmd' that consume data from +standard input. When standard input is a seekable file, the subprocess +will pick up with the next character not yet processed by `m4'; when it +is a pipe or other non-seekable file, there is no guarantee how much +data will already be buffered by `m4' and thus unavailable to the child. + + +File: m4.info, Node: Esyscmd, Next: Sysval, Prev: Syscmd, Up: Shell commands + +13.3 Reading the output of commands +=================================== + +If you want `m4' to read the output of a shell command, use `esyscmd': + + -- Builtin: esyscmd (SHELL-COMMAND) + Expands to the standard output of the shell command SHELL-COMMAND. + + Prior to executing the command, `m4' flushes its buffers. The + default standard input and standard error of SHELL-COMMAND are the + same as those of `m4'. The error output of SHELL-COMMAND is not a + part of the expansion: it will appear along with the error output + of `m4'. + + By default, the SHELL-COMMAND will be used as the argument to the + `-c' option of the `/bin/sh' shell (or the version of `sh' + specified by `command -p getconf PATH', if your system supports + that). If you prefer a different shell, the `configure' script + can be given the option `--with-syscmd-shell=LOCATION' to set the + location of an alternative shell at GNU `m4' installation; the + alternative shell must still support `-c'. + + The macro `esyscmd' is recognized only with parameters. + + define(`foo', `FOO') + => + esyscmd(`echo foo') + =>FOO + => + + Note how the expansion of `esyscmd' keeps the trailing newline of +the command, as well as using the newline that appeared after the macro. + + Just as with `syscmd', care must be exercised when sharing standard +input between `m4' and the child process of `esyscmd'. + + +File: m4.info, Node: Sysval, Next: Mkstemp, Prev: Esyscmd, Up: Shell commands + +13.4 Exit status +================ + +To see whether a shell command succeeded, use `sysval': + + -- Builtin: sysval + Expands to the exit status of the last shell command run with + `syscmd' or `esyscmd'. Expands to 0 if no command has been run + yet. + + sysval + =>0 + syscmd(`false') + => + ifelse(sysval, `0', `zero', `non-zero') + =>non-zero + syscmd(`exit 2') + => + sysval + =>2 + syscmd(`true') + => + sysval + =>0 + esyscmd(`false') + => + ifelse(sysval, `0', `zero', `non-zero') + =>non-zero + esyscmd(`echo dnl && exit 127') + => + sysval + =>127 + esyscmd(`true') + => + sysval + =>0 + + `sysval' results in 127 if there was a problem executing the +command, for example, if the system-imposed argument length is exceeded, +or if there were not enough resources to fork. It is not possible to +distinguish between failed execution and successful execution that had +an exit status of 127, unless there was output from the child process. + + On UNIX platforms, where it is possible to detect when command +execution is terminated by a signal, rather than a normal exit, the +result is the signal number shifted left by eight bits. + + dnl This test assumes kill is a shell builtin, and that signals are + dnl recognizable. + ifdef(`__unix__', , + `errprint(` skipping: syscmd does not have unix semantics + ')m4exit(`77')')dnl + syscmd(`kill -9 $$') + => + sysval + =>2304 + syscmd() + => + sysval + =>0 + esyscmd(`kill -9 $$') + => + sysval + =>2304 + + +File: m4.info, Node: Mkstemp, Prev: Sysval, Up: Shell commands + +13.5 Making temporary files +=========================== + +Commands specified to `syscmd' or `esyscmd' might need a temporary +file, for output or for some other purpose. There is a builtin macro, +`mkstemp', for making a temporary file: + + -- Builtin: mkstemp (TEMPLATE) + -- Builtin: maketemp (TEMPLATE) + Expands to the quoted name of a new, empty file, made from the + string TEMPLATE, which should end with the string `XXXXXX'. The + six `X' characters are then replaced with random characters + matching the regular expression `[a-zA-Z0-9._-]', in order to make + the file name unique. If fewer than six `X' characters are found + at the end of `template', the result will be longer than the + template. The created file will have access permissions as if by + `chmod =rw,go=', meaning that the current umask of the `m4' + process is taken into account, and at most only the current user + can read and write the file. + + The traditional behavior, standardized by POSIX, is that + `maketemp' merely replaces the trailing `X' with the process id, + without creating a file or quoting the expansion, and without + ensuring that the resulting string is a unique file name. In + part, this means that using the same TEMPLATE twice in the same + input file will result in the same expansion. This behavior is a + security hole, as it is very easy for another process to guess the + name that will be generated, and thus interfere with a subsequent + use of `syscmd' trying to manipulate that file name. Hence, POSIX + has recommended that all new implementations of `m4' provide the + secure `mkstemp' builtin, and that users of `m4' check for its + existence. + + The expansion is void and an error issued if a temporary file could + not be created. + + The macros `mkstemp' and `maketemp' are recognized only with + parameters. + + If you try this next example, you will most likely get different +output for the two file names, since the replacement characters are +randomly chosen: + + $ m4 + define(`tmp', `oops') + => + maketemp(`/tmp/fooXXXXXX') + =>/tmp/fooa07346 + ifdef(`mkstemp', `define(`maketemp', defn(`mkstemp'))', + `define(`mkstemp', defn(`maketemp'))dnl + errprint(`warning: potentially insecure maketemp implementation + ')') + => + mkstemp(`doc') + =>docQv83Uw + + Unless you use the `--traditional' command line option (or `-G', +*note Invoking m4: Limits control.), the GNU version of `maketemp' is +secure. This means that using the same template to multiple calls will +generate multiple files. However, we recommend that you use the new +`mkstemp' macro, introduced in GNU M4 1.4.8, which is secure even in +traditional mode. Also, as of M4 1.4.11, the secure implementation +quotes the resulting file name, so that you are guaranteed to know what +file was created even if the random file name happens to match an +existing macro. Notice that this example is careful to use `defn' to +avoid unintended expansion of `foo'. + + $ m4 + define(`foo', `errprint(`oops')') + => + syscmd(`rm -f foo-??????')sysval + =>0 + define(`file1', maketemp(`foo-XXXXXX'))dnl + ifelse(esyscmd(`echo \` foo-?????? \''), ` foo-?????? ', + `no file', `created') + =>created + define(`file2', maketemp(`foo-XX'))dnl + define(`file3', mkstemp(`foo-XXXXXX'))dnl + ifelse(len(defn(`file1')), len(defn(`file2')), + `same length', `different') + =>same length + ifelse(defn(`file1'), defn(`file2'), `same', `different file') + =>different file + ifelse(defn(`file2'), defn(`file3'), `same', `different file') + =>different file + ifelse(defn(`file1'), defn(`file3'), `same', `different file') + =>different file + syscmd(`rm 'defn(`file1') defn(`file2') defn(`file3')) + => + sysval + =>0 + + +File: m4.info, Node: Miscellaneous, Next: Frozen files, Prev: Shell commands, Up: Top + +14 Miscellaneous builtin macros +******************************* + +This chapter describes various builtins, that do not really belong in +any of the previous chapters. + +* Menu: + +* Errprint:: Printing error messages +* Location:: Printing current location +* M4exit:: Exiting from `m4' + + +File: m4.info, Node: Errprint, Next: Location, Up: Miscellaneous + +14.1 Printing error messages +============================ + +You can print error messages using `errprint': + + -- Builtin: errprint (MESSAGE, ...) + Prints MESSAGE and the rest of the arguments to standard error, + separated by spaces. Standard error is used, regardless of the + `--debugfile' option (*note Invoking m4: Debugging options.). + + The expansion of `errprint' is void. The macro `errprint' is + recognized only with parameters. + + errprint(`Invalid arguments to forloop + ') + error-->Invalid arguments to forloop + => + errprint(`1')errprint(`2',`3 + ') + error-->12 3 + => + + A trailing newline is _not_ printed automatically, so it should be +supplied as part of the argument, as in the example. Unfortunately, the +exact output of `errprint' is not very portable to other `m4' +implementations: POSIX requires that all arguments be printed, but some +implementations of `m4' only print the first. Furthermore, some BSD +implementations always append a newline for each `errprint' call, +regardless of whether the last argument already had one, and POSIX is +silent on whether this is acceptable. + + +File: m4.info, Node: Location, Next: M4exit, Prev: Errprint, Up: Miscellaneous + +14.2 Printing current location +============================== + +To make it possible to specify the location of an error, three utility +builtins exist: + + -- Builtin: __file__ + -- Builtin: __line__ + -- Builtin: __program__ + Expand to the quoted name of the current input file, the current + input line number in that file, and the quoted name of the current + invocation of `m4'. + + errprint(__program__:__file__:__line__: `input error + ') + error-->m4:stdin:1: input error + => + + Line numbers start at 1 for each file. If the file was found due to +the `-I' option or `M4PATH' environment variable, that is reflected in +the file name. The syncline option (`-s', *note Invoking m4: +Preprocessor features.), and the `f' and `l' flags of `debugmode' +(*note Debug Levels::), also use this notion of current file and line. +Redefining the three location macros has no effect on syncline, debug, +warning, or error message output. + + This example reuses the file `incl.m4' mentioned earlier (*note +Include::): + + $ m4 -I examples + define(`foo', ``$0' called at __file__:__line__') + => + foo + =>foo called at stdin:2 + include(`incl.m4') + =>Include file start + =>foo called at examples/incl.m4:2 + =>Include file end + => + + The location of macros invoked during the rescanning of macro +expansion text corresponds to the location in the file where the +expansion was triggered, regardless of how many newline characters the +expansion text contains. As of GNU M4 1.4.8, the location of text +wrapped with `m4wrap' (*note M4wrap::) is the point at which the +`m4wrap' was invoked. Previous versions, however, behaved as though +wrapped text came from line 0 of the file "". + + define(`echo', `$@') + => + define(`foo', `echo(__line__ + __line__)') + => + echo(__line__ + __line__) + =>4 + =>5 + m4wrap(`foo + ') + => + foo(errprint(__line__ + __line__ + )) + error-->8 + error-->9 + =>8 + =>8 + __line__ + =>11 + m4wrap(`__line__ + ') + => + ^D + =>12 + =>6 + =>6 + + The `__program__' macro behaves like `$0' in shell terminology. If +you invoke `m4' through an absolute path or a link with a different +spelling, rather than by relying on a `PATH' search for plain `m4', it +will affect how `__program__' expands. The intent is that you can use +it to produce error messages with the same formatting that `m4' +produces internally. It can also be used within `syscmd' (*note +Syscmd::) to pick the same version of `m4' that is currently running, +rather than whatever version of `m4' happens to be first in `PATH'. It +was first introduced in GNU M4 1.4.6. + + +File: m4.info, Node: M4exit, Prev: Location, Up: Miscellaneous + +14.3 Exiting from `m4' +====================== + +If you need to exit from `m4' before the entire input has been read, +you can use `m4exit': + + -- Builtin: m4exit ([CODE = `0']) + Causes `m4' to exit, with exit status CODE. If CODE is left out, + the exit status is zero. If CODE cannot be parsed, or is outside + the range of 0 to 255, the exit status is one. No further input + is read, and all wrapped and diverted text is discarded. + + m4wrap(`This text is lost due to `m4exit'.') + => + divert(`1') So is this. + divert + => + m4exit And this is never read. + + A common use of this is to abort processing: + + -- Composite: fatal_error (MESSAGE) + Abort processing with an error message and non-zero status. Prefix + MESSAGE with details about where the error occurred, and print the + resulting string to standard error. + + define(`fatal_error', + `errprint(__program__:__file__:__line__`: fatal error: $* + ')m4exit(`1')') + => + fatal_error(`this is a BAD one, buster') + error-->m4:stdin:4: fatal error: this is a BAD one, buster + + After this macro call, `m4' will exit with exit status 1. This macro +is only intended for error exits, since the normal exit procedures are +not followed, i.e., diverted text is not undiverted, and saved text +(*note M4wrap::) is not reread. (This macro could be made more robust +to earlier versions of `m4'. You should try to see if you can find +weaknesses and correct them; or *note Answers: Improved fatal_error.). + + Note that it is still possible for the exit status to be different +than what was requested by `m4exit'. If `m4' detects some other error, +such as a write error on standard output, the exit status will be +non-zero even if `m4exit' requested zero. + + If standard input is seekable, then the file will be positioned at +the next unread character. If it is a pipe or other non-seekable file, +then there are no guarantees how much data `m4' might have read into +buffers, and thus discarded. + + +File: m4.info, Node: Frozen files, Next: Compatibility, Prev: Miscellaneous, Up: Top + +15 Fast loading of frozen state +******************************* + +Some bigger `m4' applications may be built over a common base +containing hundreds of definitions and other costly initializations. +Usually, the common base is kept in one or more declarative files, +which files are listed on each `m4' invocation prior to the user's +input file, or else each input file uses `include'. + + Reading the common base of a big application, over and over again, +may be time consuming. GNU `m4' offers some machinery to speed up the +start of an application using lengthy common bases. + +* Menu: + +* Using frozen files:: Using frozen files +* Frozen file format:: Frozen file format + + +File: m4.info, Node: Using frozen files, Next: Frozen file format, Up: Frozen files + +15.1 Using frozen files +======================= + +Suppose a user has a library of `m4' initializations in `base.m4', +which is then used with multiple input files: + + $ m4 base.m4 input1.m4 + $ m4 base.m4 input2.m4 + $ m4 base.m4 input3.m4 + + Rather than spending time parsing the fixed contents of `base.m4' +every time, the user might rather execute: + + $ m4 -F base.m4f base.m4 + +once, and further execute, as often as needed: + + $ m4 -R base.m4f input1.m4 + $ m4 -R base.m4f input2.m4 + $ m4 -R base.m4f input3.m4 + +with the varying input. The first call, containing the `-F' option, +only reads and executes file `base.m4', defining various application +macros and computing other initializations. Once the input file +`base.m4' has been completely processed, GNU `m4' produces in +`base.m4f' a "frozen" file, that is, a file which contains a kind of +snapshot of the `m4' internal state. + + Later calls, containing the `-R' option, are able to reload the +internal state of `m4', from `base.m4f', _prior_ to reading any other +input files. This means instead of starting with a virgin copy of +`m4', input will be read after having effectively recovered the effect +of a prior run. In our example, the effect is the same as if file +`base.m4' has been read anew. However, this effect is achieved a lot +faster. + + Only one frozen file may be created or read in any one `m4' +invocation. It is not possible to recover two frozen files at once. +However, frozen files may be updated incrementally, through using `-R' +and `-F' options simultaneously. For example, if some care is taken, +the command: + + $ m4 file1.m4 file2.m4 file3.m4 file4.m4 + +could be broken down in the following sequence, accumulating the same +output: + + $ m4 -F file1.m4f file1.m4 + $ m4 -R file1.m4f -F file2.m4f file2.m4 + $ m4 -R file2.m4f -F file3.m4f file3.m4 + $ m4 -R file3.m4f file4.m4 + + Some care is necessary because not every effort has been made for +this to work in all cases. In particular, the trace attribute of +macros is not handled, nor the current setting of `changeword'. +Currently, `m4wrap' and `sysval' also have problems. Also, +interactions for some options of `m4', being used in one call and not +in the next, have not been fully analyzed yet. On the other end, you +may be confident that stacks of `pushdef' definitions are handled +correctly, as well as undefined or renamed builtins, and changed +strings for quotes or comments. And future releases of GNU M4 will +improve on the utility of frozen files. + + When an `m4' run is to be frozen, the automatic undiversion which +takes place at end of execution is inhibited. Instead, all positively +numbered diversions are saved into the frozen file. The active +diversion number is also transmitted. + + A frozen file to be reloaded need not reside in the current +directory. It is looked up the same way as an `include' file (*note +Search Path::). + + If the frozen file was generated with a newer version of `m4', and +contains directives that an older `m4' cannot parse, attempting to load +the frozen file with option `-R' will cause `m4' to exit with status 63 +to indicate version mismatch. + + +File: m4.info, Node: Frozen file format, Prev: Using frozen files, Up: Frozen files + +15.2 Frozen file format +======================= + +Frozen files are sharable across architectures. It is safe to write a +frozen file on one machine and read it on another, given that the +second machine uses the same or newer version of GNU `m4'. It is +conventional, but not required, to give a frozen file the suffix of +`.m4f'. + + These are simple (editable) text files, made up of directives, each +starting with a capital letter and ending with a newline (<NL>). +Wherever a directive is expected, the character `#' introduces a +comment line; empty lines are also ignored if they are not part of an +embedded string. In the following descriptions, each LEN refers to the +length of the corresponding strings STR in the next line of input. +Numbers are always expressed in decimal. There are no escape +characters. The directives are: + +`C LEN1 , LEN2 <NL> STR1 STR2 <NL>' + Uses STR1 and STR2 as the begin-comment and end-comment strings. + If omitted, then `#' and <NL> are the comment delimiters. + +`D NUMBER, LEN <NL> STR <NL>' + Selects diversion NUMBER, making it current, then copy STR in the + current diversion. NUMBER may be a negative number for a + non-existing diversion. To merely specify an active selection, + use this command with an empty STR. With 0 as the diversion + NUMBER, STR will be issued on standard output at reload time. GNU + `m4' will not produce the `D' directive with non-zero length for + diversion 0, but this can be done with manual edits. This + directive may appear more than once for the same diversion, in + which case the diversion is the concatenation of the various uses. + If omitted, then diversion 0 is current. + +`F LEN1 , LEN2 <NL> STR1 STR2 <NL>' + Defines, through `pushdef', a definition for STR1 expanding to the + function whose builtin name is STR2. If the builtin does not + exist (for example, if the frozen file was produced by a copy of + `m4' compiled with changeword support, but the version of `m4' + reloading was compiled without it), the reload is silent, but any + subsequent use of the definition of STR1 will result in a warning. + This directive may appear more than once for the same name, and + its order, along with `T', is important. If omitted, you will + have no access to any builtins. + +`Q LEN1 , LEN2 <NL> STR1 STR2 <NL>' + Uses STR1 and STR2 as the begin-quote and end-quote strings. If + omitted, then ``' and `'' are the quote delimiters. + +`T LEN1 , LEN2 <NL> STR1 STR2 <NL>' + Defines, though `pushdef', a definition for STR1 expanding to the + text given by STR2. This directive may appear more than once for + the same name, and its order, along with `F', is important. + +`V NUMBER <NL>' + Confirms the format of the file. `m4' 1.4.16 only creates and + understands frozen files where NUMBER is 1. This directive must + be the first non-comment in the file, and may not appear more than + once. + + +File: m4.info, Node: Compatibility, Next: Answers, Prev: Frozen files, Up: Top + +16 Compatibility with other versions of `m4' +******************************************** + +This chapter describes the many of the differences between this +implementation of `m4', and of other implementations found under UNIX, +such as System V Release 3, Solaris, and BSD flavors. In particular, +it lists the known differences and extensions to POSIX. However, the +list is not necessarily comprehensive. + + At the time of this writing, POSIX 2001 (also known as IEEE Std +1003.1-2001) is the latest standard, although a new version of POSIX is +under development and includes several proposals for modifying what +`m4' is required to do. The requirements for `m4' are shared between +SUSv3 and POSIX, and can be viewed at +`http://www.opengroup.org/onlinepubs/000095399/utilities/m4.html'. + +* Menu: + +* Extensions:: Extensions in GNU M4 +* Incompatibilities:: Facilities in System V m4 not in GNU M4 +* Other Incompatibilities:: Other incompatibilities + + +File: m4.info, Node: Extensions, Next: Incompatibilities, Up: Compatibility + +16.1 Extensions in GNU M4 +========================= + +This version of `m4' contains a few facilities that do not exist in +System V `m4'. These extra facilities are all suppressed by using the +`-G' command line option (*note Invoking m4: Limits control.), unless +overridden by other command line options. + + * In the `$N' notation for macro arguments, N can contain several + digits, while the System V `m4' only accepts one digit. This + allows macros in GNU `m4' to take any number of arguments, and not + only nine (*note Arguments::). + + This means that `define(`foo', `$11')' is ambiguous between + implementations. To portably choose between grabbing the first + parameter and appending 1 to the expansion, or grabbing the + eleventh parameter, you can do the following: + + define(`a1', `A1') + => + dnl First argument, concatenated with 1 + define(`_1', `$1')define(`first1', `_1($@)1') + => + dnl Eleventh argument, portable + define(`_9', `$9')define(`eleventh', `_9(shift(shift($@)))') + => + dnl Eleventh argument, GNU style + define(`Eleventh', `$11') + => + first1(`a', `b', `c', `d', `e', `f', `g', `h', `i', `j', `k') + =>A1 + eleventh(`a', `b', `c', `d', `e', `f', `g', `h', `i', `j', `k') + =>k + Eleventh(`a', `b', `c', `d', `e', `f', `g', `h', `i', `j', `k') + =>k + + Also see the `argn' macro (*note Shift::). + + * The `divert' (*note Divert::) macro can manage more than 9 + diversions. GNU `m4' treats all positive numbers as valid + diversions, rather than discarding diversions greater than 9. + + * Files included with `include' and `sinclude' are sought in a user + specified search path, if they are not found in the working + directory. The search path is specified by the `-I' option and the + `M4PATH' environment variable (*note Search Path::). + + * Arguments to `undivert' can be non-numeric, in which case the named + file will be included uninterpreted in the output (*note + Undivert::). + + * Formatted output is supported through the `format' builtin, which + is modeled after the C library function `printf' (*note Format::). + + * Searches and text substitution through basic regular expressions + are supported by the `regexp' (*note Regexp::) and `patsubst' + (*note Patsubst::) builtins. Some BSD implementations use + extended regular expressions instead. + + * The output of shell commands can be read into `m4' with `esyscmd' + (*note Esyscmd::). + + * There is indirect access to any builtin macro with `builtin' + (*note Builtin::). + + * Macros can be called indirectly through `indir' (*note Indir::). + + * The name of the program, the current input file, and the current + input line number are accessible through the builtins + `__program__', `__file__', and `__line__' (*note Location::). + + * The format of the output from `dumpdef' and macro tracing can be + controlled with `debugmode' (*note Debug Levels::). + + * The destination of trace and debug output can be controlled with + `debugfile' (*note Debug Output::). + + * The `maketemp' (*note Mkstemp::) macro behaves like `mkstemp', + creating a new file with a unique name on every invocation, rather + than following the insecure behavior of replacing the trailing `X' + characters with the `m4' process id. + + * POSIX only requires support for the command line options `-s', + `-D', and `-U', so all other options accepted by GNU M4 are + extensions. *Note Invoking m4::, for a description of these + options. + + The debugging and tracing facilities in GNU `m4' are much more + extensive than in most other versions of `m4'. + + +File: m4.info, Node: Incompatibilities, Next: Other Incompatibilities, Prev: Extensions, Up: Compatibility + +16.2 Facilities in System V `m4' not in GNU `m4' +================================================ + +The version of `m4' from System V contains a few facilities that have +not been implemented in GNU `m4' yet. Additionally, POSIX requires +some behaviors that GNU `m4' has not implemented yet. Relying on these +behaviors is non-portable, as a future release of GNU `m4' may change. + + * POSIX requires support for multiple arguments to `defn', without + any clarification on how `defn' behaves when one of the multiple + arguments names a builtin. System V `m4' and some other + implementations allow mixing builtins and text macros into a single + macro. GNU `m4' only supports joining multiple text arguments, + although a future implementation may lift this restriction to + behave more like System V. The only portable way to join text + macros with builtins is via helper macros and implicit + concatenation of macro results. + + * POSIX requires an application to exit with non-zero status if it + wrote an error message to stderr. This has not yet been + consistently implemented for the various builtins that are + required to issue an error (such as `eval' (*note Eval::) when an + argument cannot be parsed). + + * Some traditional implementations only allow reading standard input + once, but GNU `m4' correctly handles multiple instances of `-' on + the command line. + + * POSIX requires `m4wrap' (*note M4wrap::) to act in FIFO (first-in, + first-out) order, but GNU `m4' currently uses LIFO order. + Furthermore, POSIX states that only the first argument to `m4wrap' + is saved for later evaluation, but GNU `m4' saves and processes + all arguments, with output separated by spaces. + + * POSIX states that builtins that require arguments, but are called + without arguments, have undefined behavior. Traditional + implementations simply behave as though empty strings had been + passed. For example, `a`'define`'b' would expand to `ab'. But + GNU `m4' ignores certain builtins if they have missing arguments, + giving `adefineb' for the above example. + + * Traditional implementations handle `define(`f',`1')' (*note + Define::) by undefining the entire stack of previous definitions, + and if doing `undefine(`f')' first. GNU `m4' replaces just the top + definition on the stack, as if doing `popdef(`f')' followed by + `pushdef(`f',`1')'. POSIX allows either behavior. + + * POSIX 2001 requires `syscmd' (*note Syscmd::) to evaluate command + output for macro expansion, but this was a mistake that is + anticipated to be corrected in the next version of POSIX. GNU + `m4' follows traditional behavior in `syscmd' where output is not + rescanned, and provides the extension `esyscmd' that does scan the + output. + + * At one point, POSIX required `changequote(ARG)' (*note + Changequote::) to use newline as the close quote, but this was a + bug, and the next version of POSIX is anticipated to state that + using empty strings or just one argument is unspecified. + Meanwhile, the GNU `m4' behavior of treating an empty end-quote + delimiter as `'' is not portable, as Solaris treats it as + repeating the start-quote delimiter, and BSD treats it as leaving + the previous end-quote delimiter unchanged. For predictable + results, never call changequote with just one argument, or with + empty strings for arguments. + + * At one point, POSIX required `changecom(ARG,)' (*note Changecom::) + to make it impossible to end a comment, but this is a bug, and the + next version of POSIX is anticipated to state that using empty + strings is unspecified. Meanwhile, the GNU `m4' behavior of + treating an empty end-comment delimiter as newline is not + portable, as BSD treats it as leaving the previous end-comment + delimiter unchanged. It is also impossible in BSD implementations + to disable comments, even though that is required by POSIX. For + predictable results, never call changecom with empty strings for + arguments. + + * Most implementations of `m4' give macros a higher precedence than + comments when parsing, meaning that if the start delimiter given to + `changecom' (*note Changecom::) starts with a macro name, comments + are effectively disabled. POSIX does not specify what the + precedence is, so this version of GNU `m4' parser recognizes + comments, then macros, then quoted strings. + + * Traditional implementations allow argument collection, but not + string and comment processing, to span file boundaries. Thus, if + `a.m4' contains `len(', and `b.m4' contains `abc)', `m4 a.m4 b.m4' + outputs `3' with traditional `m4', but gives an error message that + the end of file was encountered inside a macro with GNU `m4'. On + the other hand, traditional implementations do end of file + processing for files included with `include' or `sinclude' (*note + Include::), while GNU `m4' seamlessly integrates the content of + those files. Thus `include(`a.m4')include(`b.m4')' will output + `3' instead of giving an error. + + * Traditional `m4' treats `traceon' (*note Trace::) without + arguments as a global variable, independent of named macro tracing. + Also, once a macro is undefined, named tracing of that macro is + lost. On the other hand, when GNU `m4' encounters `traceon' + without arguments, it turns tracing on for all existing + definitions at the time, but does not trace future definitions; + `traceoff' without arguments turns tracing off for all definitions + regardless of whether they were also traced by name; and tracing + by name, such as with `-tfoo' at the command line or + `traceon(`foo')' in the input, is an attribute that is preserved + even if the macro is currently undefined. + + Additionally, while POSIX requires trace output, it makes no + demands on the formatting of that output. Parsing trace output is + not guaranteed to be reliable, even between different releases of + GNU M4; however, the intent is that any future changes in trace + output will only occur under the direction of additional + `debugmode' flags (*note Debug Levels::). + + * POSIX requires `eval' (*note Eval::) to treat all operators with + the same precedence as C. However, earlier versions of GNU `m4' + followed the traditional behavior of other `m4' implementations, + where bitwise and logical negation (`~' and `!') have lower + precedence than equality operators; and where equality operators + (`==' and `!=') had the same precedence as relational operators + (such as `<'). Use explicit parentheses to ensure proper + precedence. As extensions to POSIX, GNU `m4' gives well-defined + semantics to operations that C leaves undefined, such as when + overflow occurs, when shifting negative numbers, or when + performing division by zero. POSIX also requires `=' to cause an + error, but many traditional implementations allowed it as an alias + for `=='. + + * POSIX 2001 requires `translit' (*note Translit::) to treat each + character of the second and third arguments literally. However, + it is anticipated that the next version of POSIX will allow the + GNU `m4' behavior of treating `-' as a range operator. + + * POSIX requires `m4' to honor the locale environment variables of + `LANG', `LC_ALL', `LC_CTYPE', `LC_MESSAGES', and `NLSPATH', but + this has not yet been implemented in GNU `m4'. + + * POSIX states that only unquoted leading newlines and blanks (that + is, space and tab) are ignored when collecting macro arguments. + However, this appears to be a bug in POSIX, since most traditional + implementations also ignore all whitespace (formfeed, carriage + return, and vertical tab). GNU `m4' follows tradition and ignores + all leading unquoted whitespace. + + * A strictly-compliant POSIX client is not allowed to use + command-line arguments not specified by POSIX. However, since + this version of M4 ignores `POSIXLY_CORRECT' and enables the option + `--gnu' by default (*note Invoking m4: Limits control.), a client + desiring to be strictly compliant has no way to disable GNU + extensions that conflict with POSIX when directly invoking the + compiled `m4'. A future version of `GNU' M4 will honor the + environment variable `POSIXLY_CORRECT', implicitly enabling + `--traditional' if it is set, in order to allow a + strictly-compliant client. In the meantime, a client needing + strict POSIX compliance can use the workaround of invoking a shell + script wrapper, where the wrapper then adds `--traditional' to the + arguments passed to the compiled `m4'. + + +File: m4.info, Node: Other Incompatibilities, Prev: Incompatibilities, Up: Compatibility + +16.3 Other incompatibilities +============================ + +There are a few other incompatibilities between this implementation of +`m4', and the System V version. + + * GNU `m4' implements sync lines differently from System V `m4', + when text is being diverted. GNU `m4' outputs the sync lines when + the text is being diverted, and System V `m4' when the diverted + text is being brought back. + + The problem is which lines and file names should be attached to + text that is being, or has been, diverted. System V `m4' regards + all the diverted text as being generated by the source line + containing the `undivert' call, whereas GNU `m4' regards the + diverted text as being generated at the time it is diverted. + + The sync line option is used mostly when using `m4' as a front end + to a compiler. If a diverted line causes a compiler error, the + error messages should most probably refer to the place where the + diversion was made, and not where it was inserted again. + + divert(2)2 + divert(1)1 + divert`'0 + =>#line 3 "stdin" + =>0 + ^D + =>#line 2 "stdin" + =>1 + =>#line 1 "stdin" + =>2 + + The current `m4' implementation has a limitation that the syncline + output at the start of each diversion occurs no matter what, even + if the previous diversion did not end with a newline. This goes + contrary to the claim that synclines appear on a line by + themselves, so this limitation may be corrected in a future + version of `m4'. In the meantime, when using `-s', it is wisest + to make sure all diversions end with newline. + + * GNU `m4' makes no attempt at prohibiting self-referential + definitions like: + + define(`x', `x') + => + define(`x', `x ') + => + + There is nothing inherently wrong with defining `x' to return `x'. + The wrong thing is to expand `x' unquoted, because that would + cause an infinite rescan loop. In `m4', one might use macros to + hold strings, as we do for variables in other programming + languages, further checking them with: + + ifelse(defn(`HOLDER'), `VALUE', ...) + + In cases like this one, an interdiction for a macro to hold its + own name would be a useless limitation. Of course, this leaves + more rope for the GNU `m4' user to hang himself! Rescanning hangs + may be avoided through careful programming, a little like for + endless loops in traditional programming languages. + + +File: m4.info, Node: Answers, Next: Copying This Package, Prev: Compatibility, Up: Top + +17 Correct version of some examples +*********************************** + +Some of the examples in this manuals are buggy or not very robust, for +demonstration purposes. Improved versions of these composite macros are +presented here. + +* Menu: + +* Improved exch:: Solution for `exch' +* Improved forloop:: Solution for `forloop' +* Improved foreach:: Solution for `foreach' +* Improved copy:: Solution for `copy' +* Improved m4wrap:: Solution for `m4wrap' +* Improved cleardivert:: Solution for `cleardivert' +* Improved capitalize:: Solution for `capitalize' +* Improved fatal_error:: Solution for `fatal_error' + + +File: m4.info, Node: Improved exch, Next: Improved forloop, Up: Answers + +17.1 Solution for `exch' +======================== + +The `exch' macro (*note Arguments::) as presented requires clients to +double quote their arguments. A nicer definition, which lets clients +follow the rule of thumb of one level of quoting per level of +parentheses, involves adding quotes in the definition of `exch', as +follows: + + define(`exch', ``$2', `$1'') + => + define(exch(`expansion text', `macro')) + => + macro + =>expansion text + + +File: m4.info, Node: Improved forloop, Next: Improved foreach, Prev: Improved exch, Up: Answers + +17.2 Solution for `forloop' +=========================== + +The `forloop' macro (*note Forloop::) as presented earlier can go into +an infinite loop if given an iterator that is not parsed as a macro +name. It does not do any sanity checking on its numeric bounds, and +only permits decimal numbers for bounds. Here is an improved version, +shipped as `m4-1.4.16/examples/forloop2.m4'; this version also +optimizes overhead by calling four macros instead of six per iteration +(excluding those in TEXT), by not dereferencing the ITERATOR in the +helper `_forloop'. + + $ m4 -d -I examples + undivert(`forloop2.m4')dnl + =>divert(`-1') + =># forloop(var, from, to, stmt) - improved version: + =># works even if VAR is not a strict macro name + =># performs sanity check that FROM is larger than TO + =># allows complex numerical expressions in TO and FROM + =>define(`forloop', `ifelse(eval(`($2) <= ($3)'), `1', + => `pushdef(`$1')_$0(`$1', eval(`$2'), + => eval(`$3'), `$4')popdef(`$1')')') + =>define(`_forloop', + => `define(`$1', `$2')$4`'ifelse(`$2', `$3', `', + => `$0(`$1', incr(`$2'), `$3', `$4')')') + =>divert`'dnl + include(`forloop2.m4') + => + forloop(`i', `2', `1', `no iteration occurs') + => + forloop(`', `1', `2', ` odd iterator name') + => odd iterator name odd iterator name + forloop(`i', `5 + 5', `0xc', ` 0x`'eval(i, `16')') + => 0xa 0xb 0xc + forloop(`i', `a', `b', `non-numeric bounds') + error-->m4:stdin:6: bad expression in eval (bad input): (a) <= (b) + => + + One other change to notice is that the improved version used `_$0' +rather than `_foreach' to invoke the helper routine. In general, this +is a good practice to follow, because then the set of macros can be +uniformly transformed. The following example shows a transformation +that doubles the current quoting and appends a suffix `2' to each +transformed macro. If `foreach' refers to the literal `_foreach', then +`foreach2' invokes `_foreach' instead of the intended `_foreach2', and +the mixing of quoting paradigms leads to an infinite recursion loop in +this example. + + $ m4 -d -L 9 -I examples + define(`arg1', `$1')include(`forloop2.m4')include(`quote.m4') + => + define(`double', `define(`$1'`2', + arg1(patsubst(dquote(defn(`$1')), `[`']', `\&\&')))') + => + double(`forloop')double(`_forloop')defn(`forloop2') + =>ifelse(eval(``($2) <= ($3)''), ``1'', + => ``pushdef(``$1'')_$0(``$1'', eval(``$2''), + => eval(``$3''), ``$4'')popdef(``$1'')'') + forloop(i, 1, 5, `ifelse(')forloop(i, 1, 5, `)') + => + changequote(`[', `]')changequote([``], ['']) + => + forloop2(i, 1, 5, ``ifelse('')forloop2(i, 1, 5, ``)'') + => + changequote`'include(`forloop.m4') + => + double(`forloop')double(`_forloop')defn(`forloop2') + =>pushdef(``$1'', ``$2'')_forloop($@)popdef(``$1'') + forloop(i, 1, 5, `ifelse(')forloop(i, 1, 5, `)') + => + changequote(`[', `]')changequote([``], ['']) + => + forloop2(i, 1, 5, ``ifelse('')forloop2(i, 1, 5, ``)'') + error-->m4:stdin:12: recursion limit of 9 exceeded, use -L<N> to change it + + One more optimization is still possible. Instead of repeatedly +assigning a variable then invoking or dereferencing it, it is possible +to pass the current iterator value as a single argument. Coupled with +`curry' if other arguments are needed (*note Composition::), or with +helper macros if the argument is needed in more than one place in the +expansion, the output can be generated with three, rather than four, +macros of overhead per iteration. Notice how the file +`m4-1.4.16/examples/forloop3.m4' rearranges the arguments of the helper +`_forloop' to take two arguments that are placed around the current +value. By splitting a balanced set of parantheses across multiple +arguments, the helper macro can now be shared by `forloop' and the new +`forloop_arg'. + + $ m4 -I examples + include(`forloop3.m4') + => + undivert(`forloop3.m4')dnl + =>divert(`-1') + =># forloop_arg(from, to, macro) - invoke MACRO(value) for + =># each value between FROM and TO, without define overhead + =>define(`forloop_arg', `ifelse(eval(`($1) <= ($2)'), `1', + => `_forloop(`$1', eval(`$2'), `$3(', `)')')') + =># forloop(var, from, to, stmt) - refactored to share code + =>define(`forloop', `ifelse(eval(`($2) <= ($3)'), `1', + => `pushdef(`$1')_forloop(eval(`$2'), eval(`$3'), + => `define(`$1',', `)$4')popdef(`$1')')') + =>define(`_forloop', + => `$3`$1'$4`'ifelse(`$1', `$2', `', + => `$0(incr(`$1'), `$2', `$3', `$4')')') + =>divert`'dnl + forloop(`i', `1', `3', ` i') + => 1 2 3 + define(`echo', `$@') + => + forloop_arg(`1', `3', ` echo') + => 1 2 3 + include(`curry.m4') + => + forloop_arg(`1', `3', `curry(`pushdef', `a')') + => + a + =>3 + popdef(`a')a + =>2 + popdef(`a')a + =>1 + popdef(`a')a + =>a + + Of course, it is possible to make even more improvements, such as +adding an optional step argument, or allowing iteration through +descending sequences. GNU Autoconf provides some of these additional +bells and whistles in its `m4_for' macro. + + +File: m4.info, Node: Improved foreach, Next: Improved copy, Prev: Improved forloop, Up: Answers + +17.3 Solution for `foreach' +=========================== + +The `foreach' and `foreachq' macros (*note Foreach::) as presented +earlier each have flaws. First, we will examine and fix the quadratic +behavior of `foreachq': + + $ m4 -I examples + include(`foreachq.m4') + => + traceon(`shift')debugmode(`aq') + => + foreachq(`x', ``1', `2', `3', `4'', `x + ')dnl + =>1 + error-->m4trace: -3- shift(`1', `2', `3', `4') + error-->m4trace: -2- shift(`1', `2', `3', `4') + =>2 + error-->m4trace: -4- shift(`1', `2', `3', `4') + error-->m4trace: -3- shift(`2', `3', `4') + error-->m4trace: -3- shift(`1', `2', `3', `4') + error-->m4trace: -2- shift(`2', `3', `4') + =>3 + error-->m4trace: -5- shift(`1', `2', `3', `4') + error-->m4trace: -4- shift(`2', `3', `4') + error-->m4trace: -3- shift(`3', `4') + error-->m4trace: -4- shift(`1', `2', `3', `4') + error-->m4trace: -3- shift(`2', `3', `4') + error-->m4trace: -2- shift(`3', `4') + =>4 + error-->m4trace: -6- shift(`1', `2', `3', `4') + error-->m4trace: -5- shift(`2', `3', `4') + error-->m4trace: -4- shift(`3', `4') + error-->m4trace: -3- shift(`4') + + Each successive iteration was adding more quoted `shift' +invocations, and the entire list contents were passing through every +iteration. In general, when recursing, it is a good idea to make the +recursion use fewer arguments, rather than adding additional quoted +uses of `shift'. By doing so, `m4' uses less memory, invokes fewer +macros, is less likely to run into machine limits, and most +importantly, performs faster. The fixed version of `foreachq' can be +found in `m4-1.4.16/examples/foreachq2.m4': + + $ m4 -I examples + include(`foreachq2.m4') + => + undivert(`foreachq2.m4')dnl + =>include(`quote.m4')dnl + =>divert(`-1') + =># foreachq(x, `item_1, item_2, ..., item_n', stmt) + =># quoted list, improved version + =>define(`foreachq', `pushdef(`$1')_$0($@)popdef(`$1')') + =>define(`_arg1q', ``$1'') + =>define(`_rest', `ifelse(`$#', `1', `', `dquote(shift($@))')') + =>define(`_foreachq', `ifelse(`$2', `', `', + => `define(`$1', _arg1q($2))$3`'$0(`$1', _rest($2), `$3')')') + =>divert`'dnl + traceon(`shift')debugmode(`aq') + => + foreachq(`x', ``1', `2', `3', `4'', `x + ')dnl + =>1 + error-->m4trace: -3- shift(`1', `2', `3', `4') + =>2 + error-->m4trace: -3- shift(`2', `3', `4') + =>3 + error-->m4trace: -3- shift(`3', `4') + =>4 + + Note that the fixed version calls unquoted helper macros in +`_foreachq' to trim elements immediately; those helper macros in turn +must re-supply the layer of quotes lost in the macro invocation. +Contrast the use of `_arg1q', which quotes the first list element, with +`_arg1' of the earlier implementation that returned the first list +element directly. Additionally, by calling the helper method +immediately, the `defn(`ITERATOR')' no longer contains unexpanded +macros. + + The astute m4 programmer might notice that the solution above still +uses more memory and macro invocations, and thus more time, than +strictly necessary. Note that `$2', which contains an arbitrarily long +quoted list, is expanded and rescanned three times per iteration of +`_foreachq'. Furthermore, every iteration of the algorithm effectively +unboxes then reboxes the list, which costs a couple of macro +invocations. It is possible to rewrite the algorithm for a bit more +speed by swapping the order of the arguments to `_foreachq' in order to +operate on an unboxed list in the first place, and by using the +fixed-length `$#' instead of an arbitrary length list as the key to end +recursion. The result is an overhead of six macro invocations per loop +(excluding any macros in TEXT), instead of eight. This alternative +approach is available as `m4-1.4.16/examples/foreach3.m4': + + $ m4 -I examples + include(`foreachq3.m4') + => + undivert(`foreachq3.m4')dnl + =>divert(`-1') + =># foreachq(x, `item_1, item_2, ..., item_n', stmt) + =># quoted list, alternate improved version + =>define(`foreachq', `ifelse(`$2', `', `', + => `pushdef(`$1')_$0(`$1', `$3', `', $2)popdef(`$1')')') + =>define(`_foreachq', `ifelse(`$#', `3', `', + => `define(`$1', `$4')$2`'$0(`$1', `$2', + => shift(shift(shift($@))))')') + =>divert`'dnl + traceon(`shift')debugmode(`aq') + => + foreachq(`x', ``1', `2', `3', `4'', `x + ')dnl + =>1 + error-->m4trace: -4- shift(`x', `x + error-->', `', `1', `2', `3', `4') + error-->m4trace: -3- shift(`x + error-->', `', `1', `2', `3', `4') + error-->m4trace: -2- shift(`', `1', `2', `3', `4') + =>2 + error-->m4trace: -4- shift(`x', `x + error-->', `1', `2', `3', `4') + error-->m4trace: -3- shift(`x + error-->', `1', `2', `3', `4') + error-->m4trace: -2- shift(`1', `2', `3', `4') + =>3 + error-->m4trace: -4- shift(`x', `x + error-->', `2', `3', `4') + error-->m4trace: -3- shift(`x + error-->', `2', `3', `4') + error-->m4trace: -2- shift(`2', `3', `4') + =>4 + error-->m4trace: -4- shift(`x', `x + error-->', `3', `4') + error-->m4trace: -3- shift(`x + error-->', `3', `4') + error-->m4trace: -2- shift(`3', `4') + + In the current version of M4, every instance of `$@' is rescanned as +it is encountered. Thus, the `foreachq3.m4' alternative uses much less +memory than `foreachq2.m4', and executes as much as 10% faster, since +each iteration encounters fewer `$@'. However, the implementation of +rescanning every byte in `$@' is quadratic in the number of bytes +scanned (for example, making the broken version in `foreachq.m4' cubic, +rather than quadratic, in behavior). A future release of M4 will +improve the underlying implementation by reusing results of previous +scans, so that both styles of `foreachq' can become linear in the +number of bytes scanned. Notice how the implementation injects an +empty argument prior to expanding `$2' within `foreachq'; the helper +macro `_foreachq' then ignores the third argument altogether, and ends +recursion when there are three arguments left because there was nothing +left to pass through `shift'. Thus, each iteration only needs one +`ifelse', rather than the two conditionals used in the version from +`foreachq2.m4'. + + So far, all of the implementations of `foreachq' presented have been +quadratic with M4 1.4.x. But `forloop' is linear, because each +iteration parses a constant amount of arguments. So, it is possible to +design a variant that uses `forloop' to do the iteration, then uses +`$@' only once at the end, giving a linear result even with older M4 +implementations. This implementation relies on the GNU extension that +`$10' expands to the tenth argument rather than the first argument +concatenated with `0'. The trick is to define an intermediate macro +that repeats the text `m4_define(`$1', `$N')$2`'', with `n' set to +successive integers corresponding to each argument. The helper macro +`_foreachq_' is needed in order to generate the literal sequences such +as `$1' into the intermediate macro, rather than expanding them as the +arguments of `_foreachq'. With this approach, no `shift' calls are +even needed! Even though there are seven macros of overhead per +iteration instead of six in `foreachq3.m4', the linear scaling is +apparent at relatively small list sizes. However, this approach will +need adjustment when a future version of M4 follows POSIX by no longer +treating `$10' as the tenth argument; the anticipation is that `${10}' +can be used instead, although that alternative syntax is not yet +supported. + + $ m4 -I examples + include(`foreachq4.m4') + => + undivert(`foreachq4.m4')dnl + =>include(`forloop2.m4')dnl + =>divert(`-1') + =># foreachq(x, `item_1, item_2, ..., item_n', stmt) + =># quoted list, version based on forloop + =>define(`foreachq', + =>`ifelse(`$2', `', `', `_$0(`$1', `$3', $2)')') + =>define(`_foreachq', + =>`pushdef(`$1', forloop(`$1', `3', `$#', + => `$0_(`1', `2', indir(`$1'))')`popdef( + => `$1')')indir(`$1', $@)') + =>define(`_foreachq_', + =>``define(`$$1', `$$3')$$2`''') + =>divert`'dnl + traceon(`shift')debugmode(`aq') + => + foreachq(`x', ``1', `2', `3', `4'', `x + ')dnl + =>1 + =>2 + =>3 + =>4 + + For yet another approach, the improved version of `foreach', +available in `m4-1.4.16/examples/foreach2.m4', simply overquotes the +arguments to `_foreach' to begin with, using `dquote_elt'. Then +`_foreach' can just use `_arg1' to remove the extra layer of quoting +that was added up front: + + $ m4 -I examples + include(`foreach2.m4') + => + undivert(`foreach2.m4')dnl + =>include(`quote.m4')dnl + =>divert(`-1') + =># foreach(x, (item_1, item_2, ..., item_n), stmt) + =># parenthesized list, improved version + =>define(`foreach', `pushdef(`$1')_$0(`$1', + => (dquote(dquote_elt$2)), `$3')popdef(`$1')') + =>define(`_arg1', `$1') + =>define(`_foreach', `ifelse(`$2', `(`')', `', + => `define(`$1', _arg1$2)$3`'$0(`$1', (dquote(shift$2)), `$3')')') + =>divert`'dnl + traceon(`shift')debugmode(`aq') + => + foreach(`x', `(`1', `2', `3', `4')', `x + ')dnl + error-->m4trace: -4- shift(`1', `2', `3', `4') + error-->m4trace: -4- shift(`2', `3', `4') + error-->m4trace: -4- shift(`3', `4') + =>1 + error-->m4trace: -3- shift(``1'', ``2'', ``3'', ``4'') + =>2 + error-->m4trace: -3- shift(``2'', ``3'', ``4'') + =>3 + error-->m4trace: -3- shift(``3'', ``4'') + =>4 + error-->m4trace: -3- shift(``4'') + + It is likewise possible to write a variant of `foreach' that +performs in linear time on M4 1.4.x; the easiest method is probably +writing a version of `foreach' that unboxes its list, then invokes +`_foreachq' as previously defined in `foreachq4.m4'. + + In summary, recursion over list elements is trickier than it +appeared at first glance, but provides a powerful idiom within `m4' +processing. As a final demonstration, both list styles are now able to +handle several scenarios that would wreak havoc on one or both of the +original implementations. This points out one other difference between +the list styles. `foreach' evaluates unquoted list elements only once, +in preparation for calling `_foreach', similary for `foreachq' as +provided by `foreachq3.m4' or `foreachq4.m4'. But `foreachq', as +provided by `foreachq2.m4', evaluates unquoted list elements twice +while visiting the first list element, once in `_arg1q' and once in +`_rest'. When deciding which list style to use, one must take into +account whether repeating the side effects of unquoted list elements +will have any detrimental effects. + + $ m4 -I examples + include(`foreach2.m4') + => + include(`foreachq2.m4') + => + dnl 0-element list: + foreach(`x', `', `<x>') / foreachq(`x', `', `<x>') + => / + dnl 1-element list of empty element + foreach(`x', `()', `<x>') / foreachq(`x', ``'', `<x>') + =><> / <> + dnl 2-element list of empty elements + foreach(`x', `(`',`')', `<x>') / foreachq(`x', ``',`'', `<x>') + =><><> / <><> + dnl 1-element list of a comma + foreach(`x', `(`,')', `<x>') / foreachq(`x', ``,'', `<x>') + =><,> / <,> + dnl 2-element list of unbalanced parentheses + foreach(`x', `(`(', `)')', `<x>') / foreachq(`x', ``(', `)'', `<x>') + =><(><)> / <(><)> + define(`ab', `oops')dnl using defn(`iterator') + foreach(`x', `(`a', `b')', `defn(`x')') /dnl + foreachq(`x', ``a', `b'', `defn(`x')') + =>ab / ab + define(`active', `ACT, IVE') + => + traceon(`active') + => + dnl list of unquoted macros; expansion occurs before recursion + foreach(`x', `(active, active)', `<x> + ')dnl + error-->m4trace: -4- active -> `ACT, IVE' + error-->m4trace: -4- active -> `ACT, IVE' + =><ACT> + =><IVE> + =><ACT> + =><IVE> + foreachq(`x', `active, active', `<x> + ')dnl + error-->m4trace: -3- active -> `ACT, IVE' + error-->m4trace: -3- active -> `ACT, IVE' + =><ACT> + error-->m4trace: -3- active -> `ACT, IVE' + error-->m4trace: -3- active -> `ACT, IVE' + =><IVE> + =><ACT> + =><IVE> + dnl list of quoted macros; expansion occurs during recursion + foreach(`x', `(`active', `active')', `<x> + ')dnl + error-->m4trace: -1- active -> `ACT, IVE' + =><ACT, IVE> + error-->m4trace: -1- active -> `ACT, IVE' + =><ACT, IVE> + foreachq(`x', ``active', `active'', `<x> + ')dnl + error-->m4trace: -1- active -> `ACT, IVE' + =><ACT, IVE> + error-->m4trace: -1- active -> `ACT, IVE' + =><ACT, IVE> + dnl list of double-quoted macro names; no expansion + foreach(`x', `(``active'', ``active'')', `<x> + ')dnl + =><active> + =><active> + foreachq(`x', ```active'', ``active''', `<x> + ')dnl + =><active> + =><active> + + +File: m4.info, Node: Improved copy, Next: Improved m4wrap, Prev: Improved foreach, Up: Answers + +17.4 Solution for `copy' +======================== + +The macro `copy' presented above is unable to handle builtin tokens +with M4 1.4.x, because it tries to pass the builtin token through the +macro `curry', where it is silently flattened to an empty string (*note +Composition::). Rather than using the problematic `curry' to work +around the limitation that `stack_foreach' expects to invoke a macro +that takes exactly one argument, we can write a new macro that lets us +form the exact two-argument `pushdef' call sequence needed, so that we +are no longer passing a builtin token through a text macro. + + -- Composite: stack_foreach_sep (MACRO, PRE, POST, SEP) + -- Composite: stack_foreach_sep_lifo (MACRO, PRE, POST, SEP) + For each of the `pushdef' definitions associated with MACRO, + expand the sequence `PRE`'definition`'POST'. Additionally, expand + SEP between definitions. `stack_foreach_sep' visits the oldest + definition first, while `stack_foreach_sep_lifo' visits the + current definition first. The expansion may dereference MACRO, + but should not modify it. There are a few special macros, such as + `defn', which cannot be used as the MACRO parameter. + + Note that `stack_foreach(`MACRO', `ACTION')' is equivalent to +`stack_foreach_sep(`MACRO', `ACTION(', `)')'. By supplying explicit +parentheses, split among the PRE and POST arguments to +`stack_foreach_sep', it is now possible to construct macro calls with +more than one argument, without passing builtin tokens through a macro +call. It is likewise possible to directly reference the stack +definitions without a macro call, by leaving PRE and POST empty. Thus, +in addition to fixing `copy' on builtin tokens, it also executes with +fewer macro invocations. + + The new macro also adds a separator that is only output after the +first iteration of the helper `_stack_reverse_sep', implemented by +prepending the original SEP to PRE and omitting a SEP argument in +subsequent iterations. Note that the empty string that separates SEP +from PRE is provided as part of the fourth argument when originally +calling `_stack_reverse_sep', and not by writing `$4`'$3' as the third +argument in the recursive call; while the other approach would give the +same output, it does so at the expense of increasing the argument size +on each iteration of `_stack_reverse_sep', which results in quadratic +instead of linear execution time. The improved stack walking macros +are available in `m4-1.4.16/examples/stack_sep.m4': + + $ m4 -I examples + include(`stack_sep.m4') + => + define(`copy', `ifdef(`$2', `errprint(`$2 already defined + ')m4exit(`1')', + `stack_foreach_sep(`$1', `pushdef(`$2',', `)')')')dnl + pushdef(`a', `1')pushdef(`a', defn(`divnum')) + => + copy(`a', `b') + => + b + =>0 + popdef(`b') + => + b + =>1 + pushdef(`c', `1')pushdef(`c', `2') + => + stack_foreach_sep_lifo(`c', `', `', `, ') + =>2, 1 + undivert(`stack_sep.m4')dnl + =>divert(`-1') + =># stack_foreach_sep(macro, pre, post, sep) + =># Invoke PRE`'defn`'POST with a single argument of each definition + =># from the definition stack of MACRO, starting with the oldest, and + =># separated by SEP between definitions. + =>define(`stack_foreach_sep', + =>`_stack_reverse_sep(`$1', `tmp-$1')'dnl + =>`_stack_reverse_sep(`tmp-$1', `$1', `$2`'defn(`$1')$3', `$4`'')') + =># stack_foreach_sep_lifo(macro, pre, post, sep) + =># Like stack_foreach_sep, but starting with the newest definition. + =>define(`stack_foreach_sep_lifo', + =>`_stack_reverse_sep(`$1', `tmp-$1', `$2`'defn(`$1')$3', `$4`'')'dnl + =>`_stack_reverse_sep(`tmp-$1', `$1')') + =>define(`_stack_reverse_sep', + =>`ifdef(`$1', `pushdef(`$2', defn(`$1'))$3`'popdef(`$1')$0( + => `$1', `$2', `$4$3')')') + =>divert`'dnl + + +File: m4.info, Node: Improved m4wrap, Next: Improved cleardivert, Prev: Improved copy, Up: Answers + +17.5 Solution for `m4wrap' +========================== + +The replacement `m4wrap' versions presented above, designed to +guarantee FIFO or LIFO order regardless of the underlying M4 +implementation, share a bug when dealing with wrapped text that looks +like parameter expansion. Note how the invocation of `m4wrapN' +interprets these parameters, while using the builtin preserves them for +their intended use. + + $ m4 -I examples + include(`wraplifo.m4') + => + m4wrap(`define(`foo', ``$0:'-$1-$*-$#-')foo(`a', `b') + ') + => + builtin(`m4wrap', ``'define(`bar', ``$0:'-$1-$*-$#-')bar(`a', `b') + ') + => + ^D + =>bar:-a-a,b-2- + =>m4wrap0:---0- + + Additionally, the computation of `_m4wrap_level' and creation of +multiple `m4wrapN' placeholders in the original examples is more +expensive in time and memory than strictly necessary. Notice how the +improved version grabs the wrapped text via `defn' to avoid parameter +expansion, then undefines `_m4wrap_text', before stripping a level of +quotes with `_arg1' to expand the text. That way, each level of +wrapping reuses the single placeholder, which starts each nesting level +in an undefined state. + + Finally, it is worth emulating the GNU M4 extension of saving all +arguments to `m4wrap', separated by a space, rather than saving just +the first argument. This is done with the `join' macro documented +previously (*note Shift::). The improved LIFO example is shipped as +`m4-1.4.16/examples/wraplifo2.m4', and can easily be converted to a +FIFO solution by swapping the adjacent invocations of `joinall' and +`defn'. + + $ m4 -I examples + include(`wraplifo2.m4') + => + undivert(`wraplifo2.m4')dnl + =>dnl Redefine m4wrap to have LIFO semantics, improved example. + =>include(`join.m4')dnl + =>define(`_m4wrap', defn(`m4wrap'))dnl + =>define(`_arg1', `$1')dnl + =>define(`m4wrap', + =>`ifdef(`_$0_text', + => `define(`_$0_text', joinall(` ', $@)defn(`_$0_text'))', + => `_$0(`_arg1(defn(`_$0_text')undefine(`_$0_text'))')dnl + =>define(`_$0_text', joinall(` ', $@))')')dnl + m4wrap(`define(`foo', ``$0:'-$1-$*-$#-')foo(`a', `b') + ') + => + m4wrap(`lifo text + m4wrap(`nested', `', `$@ + ')') + => + ^D + =>lifo text + =>foo:-a-a,b-2- + =>nested $@ + + +File: m4.info, Node: Improved cleardivert, Next: Improved capitalize, Prev: Improved m4wrap, Up: Answers + +17.6 Solution for `cleardivert' +=============================== + +The `cleardivert' macro (*note Cleardivert::) cannot, as it stands, be +called without arguments to clear all pending diversions. That is +because using undivert with an empty string for an argument is different +than using it with no arguments at all. Compare the earlier definition +with one that takes the number of arguments into account: + + define(`cleardivert', + `pushdef(`_n', divnum)divert(`-1')undivert($@)divert(_n)popdef(`_n')') + => + divert(`1')one + divert + => + cleardivert + => + undivert + =>one + => + define(`cleardivert', + `pushdef(`_num', divnum)divert(`-1')ifelse(`$#', `0', + `undivert`'', `undivert($@)')divert(_num)popdef(`_num')') + => + divert(`2')two + divert + => + cleardivert + => + undivert + => + + +File: m4.info, Node: Improved capitalize, Next: Improved fatal_error, Prev: Improved cleardivert, Up: Answers + +17.7 Solution for `capitalize' +============================== + +The `capitalize' macro (*note Patsubst::) as presented earlier does not +allow clients to follow the quoting rule of thumb. Consider the three +macros `active', `Active', and `ACTIVE', and the difference between +calling `capitalize' with the expansion of a macro, expanding the +result of a case change, and changing the case of a double-quoted +string: + + $ m4 -I examples + include(`capitalize.m4')dnl + define(`active', `act1, ive')dnl + define(`Active', `Act2, Ive')dnl + define(`ACTIVE', `ACT3, IVE')dnl + upcase(active) + =>ACT1,IVE + upcase(`active') + =>ACT3, IVE + upcase(``active'') + =>ACTIVE + downcase(ACTIVE) + =>act3,ive + downcase(`ACTIVE') + =>act1, ive + downcase(``ACTIVE'') + =>active + capitalize(active) + =>Act1 + capitalize(`active') + =>Active + capitalize(``active'') + =>_capitalize(`active') + define(`A', `OOPS') + => + capitalize(active) + =>OOPSct1 + capitalize(`active') + =>OOPSctive + + First, when `capitalize' is called with more than one argument, it +was throwing away later arguments, whereas `upcase' and `downcase' used +`$*' to collect them all. The fix is simple: use `$*' consistently. + + Next, with single-quoting, `capitalize' outputs a single character, +a set of quotes, then the rest of the characters, making it impossible +to invoke `Active' after the fact, and allowing the alternate macro `A' +to interfere. Here, the solution is to use additional quoting in the +helper macros, then pass the final over-quoted output string through +`_arg1' to remove the extra quoting and finally invoke the concatenated +portions as a single string. + + Finally, when passed a double-quoted string, the nested macro +`_capitalize' is never invoked because it ended up nested inside +quotes. This one is the toughest to fix. In short, we have no idea how +many levels of quotes are in effect on the substring being altered by +`patsubst'. If the replacement string cannot be expressed entirely in +terms of literal text and backslash substitutions, then we need a +mechanism to guarantee that the helper macros are invoked outside of +quotes. In other words, this sounds like a job for `changequote' +(*note Changequote::). By changing the active quoting characters, we +can guarantee that replacement text injected by `patsubst' always +occurs in the middle of a string that has exactly one level of +over-quoting using alternate quotes; so the replacement text closes the +quoted string, invokes the helper macros, then reopens the quoted +string. In turn, that means the replacement text has unbalanced quotes, +necessitating another round of `changequote'. + + In the fixed version below, (also shipped as +`m4-1.4.16/examples/capitalize2.m4'), `capitalize' uses the alternate +quotes of `<<[' and `]>>' (the longer strings are chosen so as to be +less likely to appear in the text being converted). The helpers +`_to_alt' and `_from_alt' merely reduce the number of characters +required to perform a `changequote', since the definition changes +twice. The outermost pair means that `patsubst' and `_capitalize_alt' +are invoked with alternate quoting; the innermost pair is used so that +the third argument to `patsubst' can contain an unbalanced `]>>'/`<<[' +pair. Note that `upcase' and `downcase' must be redefined as +`_upcase_alt' and `_downcase_alt', since they contain nested quotes but +are invoked with the alternate quoting scheme in effect. + + $ m4 -I examples + include(`capitalize2.m4')dnl + define(`active', `act1, ive')dnl + define(`Active', `Act2, Ive')dnl + define(`ACTIVE', `ACT3, IVE')dnl + define(`A', `OOPS')dnl + capitalize(active; `active'; ``active''; ```actIVE''') + =>Act1,Ive; Act2, Ive; Active; `Active' + undivert(`capitalize2.m4')dnl + =>divert(`-1') + =># upcase(text) + =># downcase(text) + =># capitalize(text) + =># change case of text, improved version + =>define(`upcase', `translit(`$*', `a-z', `A-Z')') + =>define(`downcase', `translit(`$*', `A-Z', `a-z')') + =>define(`_arg1', `$1') + =>define(`_to_alt', `changequote(`<<[', `]>>')') + =>define(`_from_alt', `changequote(<<[`]>>, <<[']>>)') + =>define(`_upcase_alt', `translit(<<[$*]>>, <<[a-z]>>, <<[A-Z]>>)') + =>define(`_downcase_alt', `translit(<<[$*]>>, <<[A-Z]>>, <<[a-z]>>)') + =>define(`_capitalize_alt', + => `regexp(<<[$1]>>, <<[^\(\w\)\(\w*\)]>>, + => <<[_upcase_alt(<<[<<[\1]>>]>>)_downcase_alt(<<[<<[\2]>>]>>)]>>)') + =>define(`capitalize', + => `_arg1(_to_alt()patsubst(<<[<<[$*]>>]>>, <<[\w+]>>, + => _from_alt()`]>>_$0_alt(<<[\&]>>)<<['_to_alt())_from_alt())') + =>divert`'dnl + + +File: m4.info, Node: Improved fatal_error, Prev: Improved capitalize, Up: Answers + +17.8 Solution for `fatal_error' +=============================== + +The `fatal_error' macro (*note M4exit::) is not robust to versions of +GNU M4 earlier than 1.4.8, where invoking `__file__' (*note Location::) +inside `m4wrap' would result in an empty string, and `__line__' +resulted in `0' even though all files start at line 1. Furthermore, +versions earlier than 1.4.6 did not support the `__program__' macro. +If you want `fatal_error' to work across the entire 1.4.x release +series, a better implementation would be: + + define(`fatal_error', + `errprint(ifdef(`__program__', `__program__', ``m4'')'dnl + `:ifelse(__line__, `0', `', + `__file__:__line__:')` fatal error: $* + ')m4exit(`1')') + => + m4wrap(`divnum(`demo of internal message') + fatal_error(`inside wrapped text')') + => + ^D + error-->m4:stdin:6: Warning: excess arguments to builtin `divnum' ignored + =>0 + error-->m4:stdin:6: fatal error: inside wrapped text + + +File: m4.info, Node: Copying This Package, Next: Copying This Manual, Prev: Answers, Up: Top + +Appendix A How to make copies of the overall M4 package +******************************************************* + +This appendix covers the license for copying the source code of the +overall M4 package. This manual is under a different set of +restrictions, covered later (*note Copying This Manual::). + +* Menu: + +* GNU General Public License:: License for copying the M4 package + + +File: m4.info, Node: GNU General Public License, Up: Copying This Package + +A.1 License for copying the M4 package +====================================== + + Version 3, 29 June 2007 + + Copyright (C) 2007 Free Software Foundation, Inc. `http://fsf.org/' + + Everyone is permitted to copy and distribute verbatim copies of this + license document, but changing it is not allowed. + +Preamble +======== + +The GNU General Public License is a free, copyleft license for software +and other kinds of works. + + The licenses for most software and other practical works are designed +to take away your freedom to share and change the works. By contrast, +the GNU General Public License is intended to guarantee your freedom to +share and change all versions of a program--to make sure it remains +free software for all its users. We, the Free Software Foundation, use +the GNU General Public License for most of our software; it applies +also to any other work released this way by its authors. You can apply +it to your programs, too. + + When we speak of free software, we are referring to freedom, not +price. Our General Public Licenses are designed to make sure that you +have the freedom to distribute copies of free software (and charge for +them if you wish), that you receive source code or can get it if you +want it, that you can change the software or use pieces of it in new +free programs, and that you know you can do these things. + + To protect your rights, we need to prevent others from denying you +these rights or asking you to surrender the rights. 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Disclaimer of Warranty. + + THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY + APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE + COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" + WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, + INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF + MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE + RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. + SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL + NECESSARY SERVICING, REPAIR OR CORRECTION. + + 16. Limitation of Liability. + + IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN + WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES + AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU + FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR + CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE + THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA + BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD + PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER + PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF + THE POSSIBILITY OF SUCH DAMAGES. + + 17. Interpretation of Sections 15 and 16. + + If the disclaimer of warranty and limitation of liability provided + above cannot be given local legal effect according to their terms, + reviewing courts shall apply local law that most closely + approximates an absolute waiver of all civil liability in + connection with the Program, unless a warranty or assumption of + liability accompanies a copy of the Program in return for a fee. + + +END OF TERMS AND CONDITIONS +=========================== + +How to Apply These Terms to Your New Programs +============================================= + +If you develop a new program, and you want it to be of the greatest +possible use to the public, the best way to achieve this is to make it +free software which everyone can redistribute and change under these +terms. + + To do so, attach the following notices to the program. It is safest +to attach them to the start of each source file to most effectively +state the exclusion of warranty; and each file should have at least the +"copyright" line and a pointer to where the full notice is found. + + ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES. + Copyright (C) YEAR NAME OF AUTHOR + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or (at + your option) any later version. + + This program is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see `http://www.gnu.org/licenses/'. + + Also add information on how to contact you by electronic and paper +mail. + + If the program does terminal interaction, make it output a short +notice like this when it starts in an interactive mode: + + PROGRAM Copyright (C) YEAR NAME OF AUTHOR + This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. + This is free software, and you are welcome to redistribute it + under certain conditions; type `show c' for details. + + The hypothetical commands `show w' and `show c' should show the +appropriate parts of the General Public License. Of course, your +program's commands might be different; for a GUI interface, you would +use an "about box". + + You should also get your employer (if you work as a programmer) or +school, if any, to sign a "copyright disclaimer" for the program, if +necessary. For more information on this, and how to apply and follow +the GNU GPL, see `http://www.gnu.org/licenses/'. + + The GNU General Public License does not permit incorporating your +program into proprietary programs. If your program is a subroutine +library, you may consider it more useful to permit linking proprietary +applications with the library. If this is what you want to do, use the +GNU Lesser General Public License instead of this License. But first, +please read `http://www.gnu.org/philosophy/why-not-lgpl.html'. + + +File: m4.info, Node: Copying This Manual, Next: Indices, Prev: Copying This Package, Up: Top + +Appendix B How to make copies of this manual +******************************************** + +This appendix covers the license for copying this manual. Note that +some of the longer examples in this manual are also distributed in the +directory `m4-1.4.16/examples/', where a more permissive license is in +effect when copying just the examples. + +* Menu: + +* GNU Free Documentation License:: License for copying this manual + diff --git a/doc/m4.info-2 b/doc/m4.info-2 new file mode 100644 index 00000000..1ac7d3b9 --- /dev/null +++ b/doc/m4.info-2 @@ -0,0 +1,909 @@ +This is m4.info, produced by makeinfo version 4.13 from m4.texinfo. + +This manual (28 February 2011) is for GNU M4 (version 1.4.16), a +package containing an implementation of the m4 macro language. + + Copyright (C) 1989-1994, 2004-2011 Free Software Foundation, Inc. + + Permission is granted to copy, distribute and/or modify this + document under the terms of the GNU Free Documentation License, + Version 1.3 or any later version published by the Free Software + Foundation; with no Invariant Sections, no Front-Cover Texts, and + no Back-Cover Texts. A copy of the license is included in the + section entitled "GNU Free Documentation License." + +INFO-DIR-SECTION Text creation and manipulation +START-INFO-DIR-ENTRY +* M4: (m4). A powerful macro processor. +END-INFO-DIR-ENTRY + + +File: m4.info, Node: GNU Free Documentation License, Up: Copying This Manual + +B.1 License for copying this manual +=================================== + + Version 1.3, 3 November 2008 + + Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. + `http://fsf.org/' + + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + 0. PREAMBLE + + The purpose of this License is to make a manual, textbook, or other + functional and useful document "free" in the sense of freedom: to + assure everyone the effective freedom to copy and redistribute it, + with or without modifying it, either commercially or + noncommercially. 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A copy of the license is included in the section entitled ``GNU + Free Documentation License''. + + If you have Invariant Sections, Front-Cover Texts and Back-Cover +Texts, replace the "with...Texts." line with this: + + with the Invariant Sections being LIST THEIR TITLES, with + the Front-Cover Texts being LIST, and with the Back-Cover Texts + being LIST. + + If you have Invariant Sections without Cover Texts, or some other +combination of the three, merge those two alternatives to suit the +situation. + + If your document contains nontrivial examples of program code, we +recommend releasing these examples in parallel under your choice of +free software license, such as the GNU General Public License, to +permit their use in free software. + + +File: m4.info, Node: Indices, Prev: Copying This Manual, Up: Top + +Appendix C Indices of concepts and macros +***************************************** + +* Menu: + +* Macro index:: Index for all `m4' macros +* Concept index:: Index for many concepts + + +File: m4.info, Node: Macro index, Next: Concept index, Up: Indices + +C.1 Index for all `m4' macros +============================= + +This index covers all `m4' builtins, as well as several useful +composite macros. References are exclusively to the places where a +macro is introduced the first time. + + +* Menu: + +* __file__: Location. (line 10) +* __gnu__: Platform macros. (line 12) +* __line__: Location. (line 11) +* __os2__: Platform macros. (line 13) +* __program__: Location. (line 12) +* __unix__: Platform macros. (line 15) +* __windows__: Platform macros. (line 17) +* argn: Shift. (line 258) +* array: Define. (line 56) +* array_set: Define. (line 57) +* builtin: Builtin. (line 9) +* capitalize: Patsubst. (line 55) +* changecom: Changecom. (line 10) +* changequote: Changequote. (line 10) +* changeword: Changeword. (line 23) +* cleardivert: Cleardivert. (line 26) +* cond: Shift. (line 53) +* copy: Composition. (line 120) +* curry: Composition. (line 68) +* debugfile: Debug Output. (line 11) +* debugmode: Debug Levels. (line 78) +* decr: Incr. (line 11) +* define: Define. (line 10) +* define_blind: Composition. (line 11) +* defn: Defn. (line 10) +* divert: Divert. (line 9) +* divnum: Divnum. (line 9) +* dnl: Dnl. (line 9) +* downcase: Patsubst. (line 54) +* dquote: Shift. (line 196) +* dquote_elt: Shift. (line 197) +* dumpdef: Dumpdef. (line 10) +* errprint: Errprint. (line 9) +* esyscmd: Esyscmd. (line 9) +* eval: Eval. (line 9) +* example: Manual. (line 40) +* exch: Arguments. (line 13) +* fatal_error: M4exit. (line 25) +* foreach: Foreach. (line 9) +* foreachq: Foreach. (line 10) +* forloop: Forloop. (line 9) +* format: Format. (line 9) +* ifdef: Ifdef. (line 10) +* ifelse: Ifelse. (line 11) +* include: Include. (line 9) +* incr: Incr. (line 10) +* index: Index macro. (line 9) +* indir: Indir. (line 9) +* join: Shift. (line 104) +* joinall: Shift. (line 105) +* len: Len. (line 9) +* m4exit: M4exit. (line 10) +* m4wrap: M4wrap. (line 14) +* maketemp: Mkstemp. (line 12) +* mkstemp: Mkstemp. (line 11) +* nargs: Pseudo Arguments. (line 13) +* os2: Platform macros. (line 14) +* patsubst: Patsubst. (line 9) +* popdef: Pushdef. (line 12) +* pushdef: Pushdef. (line 11) +* quote: Shift. (line 195) +* regexp: Regexp. (line 9) +* rename: Composition. (line 121) +* reverse: Shift. (line 32) +* shift: Shift. (line 17) +* sinclude: Include. (line 10) +* stack_foreach: Stacks. (line 12) +* stack_foreach_lifo: Stacks. (line 13) +* stack_foreach_sep: Improved copy. (line 16) +* stack_foreach_sep_lifo: Improved copy. (line 17) +* substr: Substr. (line 9) +* syscmd: Syscmd. (line 9) +* sysval: Sysval. (line 9) +* traceoff: Trace. (line 11) +* traceon: Trace. (line 10) +* translit: Translit. (line 9) +* undefine: Undefine. (line 9) +* undivert: Undivert. (line 9) +* unix: Platform macros. (line 16) +* upcase: Patsubst. (line 53) +* windows: Platform macros. (line 18) + + +File: m4.info, Node: Concept index, Prev: Macro index, Up: Indices + +C.2 Index for many concepts +=========================== + + +* Menu: + +* argument currying: Composition. (line 63) +* arguments to macros <1>: Arguments. (line 6) +* arguments to macros: Macro Arguments. (line 6) +* arguments to macros, special: Pseudo Arguments. (line 6) +* arguments, joining: Shift. (line 100) +* arguments, more than nine <1>: Improved foreach. (line 155) +* arguments, more than nine <2>: Shift. (line 252) +* arguments, more than nine: Arguments. (line 54) +* arguments, quoted macro: Quoting Arguments. (line 6) +* arguments, reversing: Shift. (line 31) +* arithmetic: Arithmetic. (line 6) +* arrays: Define. (line 52) +* avoiding quadratic behavior: Improved foreach. (line 38) +* basic regular expressions <1>: Patsubst. (line 6) +* basic regular expressions: Regexp. (line 6) +* blind macro <1>: Composition. (line 10) +* blind macro <2>: Ifelse. (line 52) +* blind macro: Inhibiting Invocation. + (line 14) +* bug reports: Bugs. (line 6) +* builtins, indirect call of: Builtin. (line 6) +* builtins, special tokens: Defn. (line 101) +* call of builtins, indirect: Builtin. (line 6) +* call of macros, indirect: Indir. (line 6) +* case statement: Ifelse. (line 69) +* changing comment delimiters: Changecom. (line 6) +* changing quote delimiters: Changequote. (line 6) +* changing syntax: Changeword. (line 6) +* characters, translating: Translit. (line 6) +* command line: Invoking m4. (line 6) +* command line, file names on the: Command line files. (line 6) +* command line, macro definitions on the: Preprocessor features. + (line 6) +* command line, options: Invoking m4. (line 10) +* commands, exit status from shell: Sysval. (line 6) +* commands, running shell: Shell commands. (line 6) +* comment delimiters, changing: Changecom. (line 6) +* comments: Comments. (line 6) +* comments, copied to output: Changecom. (line 29) +* comparing strings: Ifelse. (line 6) +* compatibility: Compatibility. (line 6) +* composing macros: Composition. (line 6) +* concatenating arguments: Shift. (line 100) +* conditional, short-circuiting: Shift. (line 51) +* conditionals: Ifdef. (line 6) +* controlling debugging output: Debug Levels. (line 6) +* copying macros: Composition. (line 116) +* counting loops: Forloop. (line 6) +* currying arguments: Composition. (line 63) +* debugging macros: Debugging. (line 6) +* debugging output, controlling: Debug Levels. (line 6) +* debugging output, saving: Debug Output. (line 6) +* decrement operator: Incr. (line 6) +* deferring expansion: M4wrap. (line 6) +* deferring output: Diversions. (line 6) +* defining new macros: Definitions. (line 6) +* definition stack <1>: Stacks. (line 6) +* definition stack: Pushdef. (line 6) +* definitions, displaying macro <1>: Dumpdef. (line 6) +* definitions, displaying macro: Defn. (line 6) +* deleting macros: Undefine. (line 6) +* deleting whitespace in input: Dnl. (line 6) +* delimiters, changing <1>: Changecom. (line 6) +* delimiters, changing: Changequote. (line 6) +* discarding diverted text: Cleardivert. (line 6) +* discarding input <1>: Divert. (line 42) +* discarding input <2>: Dnl. (line 6) +* discarding input: Ifelse. (line 6) +* displaying macro definitions: Dumpdef. (line 6) +* diversion numbers: Divnum. (line 6) +* diverted text, discarding: Cleardivert. (line 6) +* diverting output to files: Divert. (line 6) +* dumping into frozen file: Using frozen files. (line 6) +* error messages, printing: Errprint. (line 6) +* errors, fatal: Operation modes. (line 20) +* evaluation, of integer expressions: Eval. (line 6) +* examples, understanding: Manual. (line 6) +* executing shell commands: Shell commands. (line 6) +* exit status from shell commands: Sysval. (line 6) +* exiting from m4: M4exit. (line 6) +* expansion of macros: Macro expansion. (line 6) +* expansion, deferring: M4wrap. (line 6) +* expansion, tracing macro: Trace. (line 6) +* expressions, evaluation of integer: Eval. (line 6) +* expressions, regular <1>: Patsubst. (line 6) +* expressions, regular: Regexp. (line 6) +* extracting substrings: Substr. (line 6) +* fast loading of frozen files: Using frozen files. (line 6) +* fatal errors: Operation modes. (line 20) +* FDL, GNU Free Documentation License: GNU Free Documentation License. + (line 6) +* file format, frozen file: Frozen file format. (line 6) +* file inclusion <1>: Undivert. (line 13) +* file inclusion: File Inclusion. (line 6) +* file names, on the command line: Command line files. (line 6) +* files, diverting output to: Divert. (line 6) +* files, names of temporary: Mkstemp. (line 6) +* for each loops: Foreach. (line 6) +* for loops: Forloop. (line 6) +* formatted output: Format. (line 6) +* Free Documentation License (FDL), GNU: GNU Free Documentation License. + (line 6) +* frozen file format: Frozen file format. (line 6) +* frozen files for fast loading: Using frozen files. (line 6) +* General Public License (GPL), GNU: GNU General Public License. + (line 6) +* GNU extensions <1>: Extensions. (line 6) +* GNU extensions <2>: Using frozen files. (line 6) +* GNU extensions <3>: Mkstemp. (line 59) +* GNU extensions <4>: Esyscmd. (line 6) +* GNU extensions <5>: Eval. (line 125) +* GNU extensions <6>: Format. (line 6) +* GNU extensions <7>: Patsubst. (line 6) +* GNU extensions <8>: Regexp. (line 6) +* GNU extensions <9>: Undivert. (line 13) +* GNU extensions <10>: Divert. (line 54) +* GNU extensions <11>: Search Path. (line 6) +* GNU extensions <12>: Debug Output. (line 6) +* GNU extensions <13>: Debug Levels. (line 74) +* GNU extensions <14>: Builtin. (line 6) +* GNU extensions <15>: Indir. (line 6) +* GNU extensions <16>: Arguments. (line 54) +* GNU extensions <17>: Define. (line 41) +* GNU extensions: Inhibiting Invocation. + (line 14) +* GNU Free Documentation License: GNU Free Documentation License. + (line 6) +* GNU General Public License: GNU General Public License. + (line 6) +* GNU M4, history of: History. (line 6) +* GPL, GNU General Public License: GNU General Public License. + (line 6) +* history of m4: History. (line 6) +* included files, search path for: Search Path. (line 6) +* inclusion, of files <1>: Undivert. (line 13) +* inclusion, of files: File Inclusion. (line 6) +* increment operator: Incr. (line 6) +* indirect call of builtins: Builtin. (line 6) +* indirect call of macros: Indir. (line 6) +* initialization, frozen state: Using frozen files. (line 6) +* input location <1>: Location. (line 6) +* input location: Preprocessor features. + (line 28) +* input tokens: Syntax. (line 6) +* input, discarding <1>: Divert. (line 42) +* input, discarding <2>: Dnl. (line 6) +* input, discarding: Ifelse. (line 6) +* input, saving: M4wrap. (line 6) +* integer arithmetic: Arithmetic. (line 6) +* integer expression evaluation: Eval. (line 6) +* invoking m4: Invoking m4. (line 6) +* invoking macros: Invocation. (line 6) +* iterating over lists: Foreach. (line 6) +* joining arguments: Shift. (line 100) +* length of strings: Len. (line 6) +* lexical structure of words: Changeword. (line 6) +* License, code: Copying This Package. + (line 6) +* License, manual: Copying This Manual. (line 6) +* limit, nesting: Limits control. (line 43) +* literal output: Pseudo Arguments. (line 106) +* local variables: Pushdef. (line 79) +* location, input <1>: Location. (line 6) +* location, input: Preprocessor features. + (line 28) +* loops: Shift. (line 10) +* loops, counting: Forloop. (line 6) +* loops, list iteration: Foreach. (line 6) +* M4PATH: Search Path. (line 9) +* macro composition: Composition. (line 6) +* macro definitions, on the command line: Preprocessor features. + (line 6) +* macro expansion, tracing: Trace. (line 6) +* macro invocation: Invocation. (line 6) +* macro, blind <1>: Composition. (line 10) +* macro, blind <2>: Ifelse. (line 52) +* macro, blind: Inhibiting Invocation. + (line 14) +* macros, arguments to <1>: Arguments. (line 6) +* macros, arguments to: Macro Arguments. (line 6) +* macros, copying: Composition. (line 116) +* macros, debugging: Debugging. (line 6) +* macros, displaying definitions <1>: Dumpdef. (line 6) +* macros, displaying definitions: Defn. (line 6) +* macros, expansion of: Macro expansion. (line 6) +* macros, how to define new: Definitions. (line 6) +* macros, how to delete: Undefine. (line 6) +* macros, how to rename: Defn. (line 6) +* macros, indirect call of: Indir. (line 6) +* macros, quoted arguments to: Quoting Arguments. (line 6) +* macros, recursive: Shift. (line 6) +* macros, special arguments to: Pseudo Arguments. (line 6) +* macros, temporary redefinition of: Pushdef. (line 6) +* manipulating quotes: Shift. (line 191) +* messages, printing error: Errprint. (line 6) +* more than nine arguments <1>: Improved foreach. (line 155) +* more than nine arguments <2>: Shift. (line 252) +* more than nine arguments: Arguments. (line 54) +* multibranches: Ifelse. (line 69) +* names: Names. (line 6) +* nesting limit: Limits control. (line 43) +* nine arguments, more than <1>: Improved foreach. (line 155) +* nine arguments, more than <2>: Shift. (line 252) +* nine arguments, more than: Arguments. (line 54) +* numbers: Manual. (line 57) +* options, command line: Invoking m4. (line 10) +* output, diverting to files: Divert. (line 6) +* output, formatted: Format. (line 6) +* output, literal: Pseudo Arguments. (line 106) +* output, saving debugging: Debug Output. (line 6) +* overview of m4: Intro. (line 6) +* pattern substitution: Patsubst. (line 6) +* platform macros: Platform macros. (line 6) +* positional parameters, more than nine: Arguments. (line 54) +* POSIX: Extensions. (line 6) +* POSIXLY_CORRECT <1>: Incompatibilities. (line 146) +* POSIXLY_CORRECT: Invoking m4. (line 10) +* preprocessor features: Preprocessor features. + (line 6) +* printing error messages: Errprint. (line 6) +* pushdef stack <1>: Stacks. (line 6) +* pushdef stack: Pushdef. (line 6) +* quadratic behavior, avoiding: Improved foreach. (line 38) +* quote delimiters, changing: Changequote. (line 6) +* quote manipulation: Shift. (line 191) +* quoted macro arguments: Quoting Arguments. (line 6) +* quoted string: Quoted strings. (line 6) +* quoting rule of thumb: Quoting Arguments. (line 22) +* recursive macros: Shift. (line 6) +* redefinition of macros, temporary: Pushdef. (line 6) +* regular expressions <1>: Patsubst. (line 6) +* regular expressions <2>: Regexp. (line 6) +* regular expressions: Changeword. (line 6) +* reloading a frozen file: Using frozen files. (line 6) +* renaming macros <1>: Composition. (line 116) +* renaming macros: Defn. (line 6) +* reporting bugs: Bugs. (line 6) +* rescanning <1>: Other Incompatibilities. + (line 52) +* rescanning <2>: Defn. (line 61) +* rescanning <3>: Pseudo Arguments. (line 106) +* rescanning <4>: Inhibiting Invocation. + (line 87) +* rescanning: Limits control. (line 56) +* reversing arguments: Shift. (line 31) +* rule of thumb, quoting: Quoting Arguments. (line 22) +* running shell commands: Shell commands. (line 6) +* saving debugging output: Debug Output. (line 6) +* saving input: M4wrap. (line 6) +* search path for included files: Search Path. (line 6) +* shell commands, exit status from: Sysval. (line 6) +* shell commands, running: Shell commands. (line 6) +* short-circuiting conditional: Shift. (line 51) +* special arguments to macros: Pseudo Arguments. (line 6) +* stack, macro definition <1>: Stacks. (line 6) +* stack, macro definition: Pushdef. (line 6) +* standard error, output to <1>: Errprint. (line 6) +* standard error, output to <2>: Trace. (line 6) +* standard error, output to: Dumpdef. (line 6) +* status of shell commands: Sysval. (line 6) +* status, setting m4 exit: M4exit. (line 6) +* string, quoted: Quoted strings. (line 6) +* strings, length of: Len. (line 6) +* substitution by regular expression: Patsubst. (line 6) +* substrings, extracting: Substr. (line 6) +* substrings, locating: Index macro. (line 6) +* suggestions, reporting: Bugs. (line 6) +* suppressing warnings: Macro Arguments. (line 38) +* switch statement: Ifelse. (line 69) +* synchronization lines: Preprocessor features. + (line 28) +* syntax, changing: Changeword. (line 6) +* temporary file names: Mkstemp. (line 6) +* temporary redefinition of macros: Pushdef. (line 6) +* TMPDIR: Diversions. (line 10) +* tokens: Syntax. (line 6) +* tokens, builtin macro: Defn. (line 101) +* tokens, special: Other tokens. (line 6) +* tracing macro expansion: Trace. (line 6) +* translating characters: Translit. (line 6) +* undefining macros: Undefine. (line 6) +* UNIX commands, exit status from: Sysval. (line 6) +* UNIX commands, running: Shell commands. (line 6) +* variables, local: Pushdef. (line 79) +* warnings, suppressing: Macro Arguments. (line 38) +* words: Names. (line 6) +* words, lexical structure of: Changeword. (line 6) + + diff --git a/doc/m4.texinfo b/doc/m4.texinfo index fa0c6fda..1dcc8e4b 100644 --- a/doc/m4.texinfo +++ b/doc/m4.texinfo @@ -10,12 +10,10 @@ @end ifnothtml @finalout -@set beta - @c @tabchar{} @c ---------- @c The testsuite expects literal tab output in some examples, but -@c literal tabs in texinfo leads to formatting issues. +@c literal tabs in texinfo lead to formatting issues. @macro tabchar @ @c @end macro @@ -41,21 +39,20 @@ @copying -This manual (@value{UPDATED}) is for @acronym{GNU} M4 (version +This manual (@value{UPDATED}) is for GNU M4 (version @value{VERSION}), a package containing an implementation of the m4 macro language. -Copyright @copyright{} 1989, 1990, 1991, 1992, 1993, 1994, 1998, 1999, -2000, 2001, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software -Foundation, Inc. +Copyright @copyright{} 1989-1994, 2004-2011 Free Software Foundation, +Inc. @quotation Permission is granted to copy, distribute and/or modify this document -under the terms of the @acronym{GNU} Free Documentation License, +under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section -entitled ``@acronym{GNU} Free Documentation License.'' +entitled ``GNU Free Documentation License.'' @end quotation @end copying @@ -85,35 +82,38 @@ entitled ``@acronym{GNU} Free Documentation License.'' @insertcopying @end ifnottex -@acronym{GNU} @code{m4} is an implementation of the traditional UNIX macro +GNU @code{m4} is an implementation of the traditional UNIX macro processor. It is mostly SVR4 compatible, although it has some extensions (for example, handling more than 9 positional parameters to macros). @code{m4} also has builtin functions for including files, running shell commands, doing arithmetic, etc. Autoconf needs -@acronym{GNU} @code{m4} for generating @file{configure} scripts, but not for +GNU @code{m4} for generating @file{configure} scripts, but not for running them. -@acronym{GNU} @code{m4} was originally written by Ren@'e Seindal, with +GNU @code{m4} was originally written by Ren@'e Seindal, with subsequent changes by Fran@,{c}ois Pinard and other volunteers on the Internet. All names and email addresses can be found in the files @file{m4-@value{VERSION}/@/AUTHORS} and -@file{m4-@value{VERSION}/@/THANKS} from the @acronym{GNU} M4 +@file{m4-@value{VERSION}/@/THANKS} from the GNU M4 distribution. -@ifclear beta This is release @value{VERSION}. It is now considered stable: future -releases on this branch are only meant to fix bugs, increase speed, or -improve documentation. -@end ifclear - -@ifset beta -This is BETA release @value{VERSION}. This is a development release, -and as such, is prone to bugs, crashes, unforeseen features, incomplete -documentation@dots{}, therefore, use at your own peril. In case of -problems, please do not hesitate to report them (see the -@file{m4-@value{VERSION}/@/README} file in the distribution). -@xref{Experiments}. -@end ifset +releases in the 1.4.x series are only meant to fix bugs, increase speed, +or improve documentation. However@dots{} + +An experimental feature, which would improve @code{m4} usefulness, +allows for changing the syntax for what is a @dfn{word} in @code{m4}. +You should use: +@comment ignore +@example +./configure --enable-changeword +@end example +@noindent +if you want this feature compiled in. The current implementation +slows down @code{m4} considerably and is hardly acceptable. In the +future, @code{m4} 2.0 will come with a different set of new features +that provide similar capabilities, but without the inefficiencies, so +changeword will go away and @emph{you should not count on it}. @menu * Preliminaries:: Introduction and preliminaries @@ -130,8 +130,6 @@ problems, please do not hesitate to report them (see the * File Inclusion:: File inclusion * Diversions:: Diverting and undiverting output -* Modules:: Extending M4 with dynamic runtime modules - * Text handling:: Macros for text handling * Arithmetic:: Macros for doing arithmetic * Shell commands:: Macros for running shell commands @@ -158,7 +156,6 @@ Introduction and preliminaries Invoking @code{m4} * Operation modes:: Command line options for operation modes -* Dynamic loading features:: Command line options for dynamic loading * Preprocessor features:: Command line options for preprocessor features * Limits control:: Command line options for limits control * Frozen state:: Command line options for frozen state @@ -172,7 +169,6 @@ Lexical and syntactic conventions * Comments:: Comments in @code{m4} input * Other tokens:: Other kinds of input tokens * Input processing:: How @code{m4} copies input to output -* Regular expression syntax:: How @code{m4} interprets regular expressions How to invoke macros @@ -190,11 +186,9 @@ How to define new macros * Undefine:: Deleting a macro * Defn:: Renaming macros * Pushdef:: Temporarily redefining macros -* Renamesyms:: Renaming macros with regular expressions * Indir:: Indirect call of macros * Builtin:: Indirect call of builtins -* M4symbols:: Getting the defined macro names Conditionals, loops, and recursion @@ -210,17 +204,15 @@ How to debug macros and input * Dumpdef:: Displaying macro definitions * Trace:: Tracing macro calls -* Debugmode:: Controlling debugging options -* Debuglen:: Limiting debug output -* Debugfile:: Saving debugging output +* Debug Levels:: Controlling debugging output +* Debug Output:: Saving debugging output Input control * Dnl:: Deleting whitespace in input * Changequote:: Changing the quote characters * Changecom:: Changing the comment delimiters -* Changeresyntax:: Changing the regular expression syntax -* Changesyntax:: Changing the lexical structure of the input +* Changeword:: Changing the lexical structure of words * M4wrap:: Saving text until end of input File inclusion @@ -235,14 +227,6 @@ Diverting and undiverting output * Divnum:: Diversion numbers * Cleardivert:: Discarding diverted text -Extending M4 with dynamic runtime modules - -* M4modules:: Listing loaded modules -* Load:: Loading additional modules -* Unload:: Removing loaded modules -* Refcount:: Tracking module references -* Standard Modules:: Standard bundled modules - Macros for text handling * Len:: Calculating length of strings @@ -257,7 +241,6 @@ Macros for doing arithmetic * Incr:: Decrement and increment operators * Eval:: Evaluating integer expressions -* Mpeval:: Multiple precision arithmetic Macros for running shell commands @@ -266,26 +249,23 @@ Macros for running shell commands * Esyscmd:: Reading the output of commands * Sysval:: Exit status * Mkstemp:: Making temporary files -* Mkdtemp:: Making temporary directories Miscellaneous builtin macros * Errprint:: Printing error messages * Location:: Printing current location * M4exit:: Exiting from @code{m4} -* Syncoutput:: Turning on and off sync lines Fast loading of frozen state * Using frozen files:: Using frozen files -* Frozen file format 1:: Frozen file format 1 -* Frozen file format 2:: Frozen file format 2 +* Frozen file format:: Frozen file format Compatibility with other versions of @code{m4} -* Extensions:: Extensions in @acronym{GNU} M4 -* Incompatibilities:: Other incompatibilities -* Experiments:: Experimental features in @acronym{GNU} M4 +* Extensions:: Extensions in GNU M4 +* Incompatibilities:: Facilities in System V m4 not in GNU M4 +* Other Incompatibilities:: Other incompatibilities Correct version of some examples @@ -317,13 +297,13 @@ Indices of concepts and macros @node Preliminaries @chapter Introduction and preliminaries -This first chapter explains what @acronym{GNU} @code{m4} is, where @code{m4} +This first chapter explains what GNU @code{m4} is, where @code{m4} comes from, how to read and use this documentation, how to call the @code{m4} program, and how to report bugs about it. It concludes by giving tips for reading the remainder of the manual. The following chapters then detail all the features of the @code{m4} -language, as shipped in the @acronym{GNU} M4 package. +language. @menu * Intro:: Introduction to @code{m4} @@ -346,13 +326,13 @@ etc.@dots{} @code{m4} can be used either as a front-end to a compiler, or as a macro processor in its own right. The @code{m4} macro processor is widely available on all UNIXes, and has -been standardized by @acronym{POSIX}. +been standardized by POSIX. Usually, only a small percentage of users are aware of its existence. However, those who find it often become committed users. The -popularity of @acronym{GNU} Autoconf, which requires @acronym{GNU} +popularity of GNU Autoconf, which requires GNU @code{m4} for @emph{generating} @file{configure} scripts, is an incentive for many to install it, while these people will not themselves -program in @code{m4}. @acronym{GNU} @code{m4} is mostly compatible with the +program in @code{m4}. GNU @code{m4} is mostly compatible with the System V, Release 3 version, except for some minor differences. @xref{Compatibility}, for more details. @@ -368,7 +348,7 @@ debugging their @code{m4} scripts than doing real work. Beware that @section Historical references @cindex history of @code{m4} -@cindex @acronym{GNU} M4, history of +@cindex GNU M4, history of @code{GPM} was an important ancestor of @code{m4}. See C. Strachey: ``A General Purpose Macro generator'', Computer Journal 8,3 (1965), pp.@: 225 ff. @code{GPM} is also succinctly described into @@ -393,7 +373,7 @@ Originally, the Kernighan and Plauger macro-processor, and then that is, the @code{Ratfor} equivalent of @code{cpp}. Later, @code{m4} was used as a front-end for @code{Ratfor}, @code{C} and @code{Cobol}. -Ren@'e Seindal released his implementation of @code{m4}, @acronym{GNU} +Ren@'e Seindal released his implementation of @code{m4}, GNU @code{m4}, in 1990, with the aim of removing the artificial limitations in many of the traditional @code{m4} implementations, such as maximum line @@ -404,33 +384,27 @@ evolution in the form of @code{M5}: ``User's Guide to the M5 Macro Language: 2nd edition'', Electronic Announcement on comp.compilers newsgroup (1992). -Fran@,{c}ois Pinard took over maintenance of @acronym{GNU} @code{m4} in -1992, until 1994 when he released @acronym{GNU} @code{m4} 1.4, which was -the stable release for 10 years. It was at this time that @acronym{GNU} -Autoconf decided to require @acronym{GNU} @code{m4} as its underlying +Fran@,{c}ois Pinard took over maintenance of GNU @code{m4} in +1992, until 1994 when he released GNU @code{m4} 1.4, which was +the stable release for 10 years. It was at this time that GNU +Autoconf decided to require GNU @code{m4} as its underlying engine, since all other implementations of @code{m4} had too many limitations. More recently, in 2004, Paul Eggert released 1.4.1 and 1.4.2 which addressed some long standing bugs in the venerable 1.4 release. Then in 2005, Gary V. Vaughan collected together the many patches to -@acronym{GNU} @code{m4} 1.4 that were floating around the net and +GNU @code{m4} 1.4 that were floating around the net and released 1.4.3 and 1.4.4. And in 2006, Eric Blake joined the team and prepared patches for the release of 1.4.5, 1.4.6, 1.4.7, and 1.4.8. More bug fixes were incorporated in 2007, with releases 1.4.9 and 1.4.10. Eric continued with some portability fixes for 1.4.11 and -1.4.12 in 2008, and 1.4.13 in 2009. +1.4.12 in 2008, 1.4.13 in 2009, 1.4.14 and 1.4.15 in 2010, and 1.4.16 in +2011. -Additionally, in 2008, Eric rewrote the scanning engine to reduce -recursive evaluation from quadratic to linear complexity. This was -released as M4 1.6 in 2009. The 1.x branch series remains open for bug -fixes. - -Meanwhile, development was underway for new features for @code{m4}, -such as dynamic module loading and additional builtins, practically -rewriting the entire code base. This development has spurred -improvements to other @acronym{GNU} software, such as @acronym{GNU} -Libtool. @acronym{GNU} M4 2.0 is the result of this effort. +Meanwhile, development has continued on new features for @code{m4}, such +as dynamic module loading and additional builtins. When complete, +GNU @code{m4} 2.0 will start a new series of releases. @node Bugs @section Problems and bugs @@ -438,7 +412,7 @@ Libtool. @acronym{GNU} M4 2.0 is the result of this effort. @cindex reporting bugs @cindex bug reports @cindex suggestions, reporting -If you have problems with @acronym{GNU} M4 or think you've found a bug, +If you have problems with GNU M4 or think you've found a bug, please report it. Before reporting a bug, make sure you've actually found a real bug. Carefully reread the documentation and see if it really says you can do what you're trying to do. If it's not clear @@ -454,8 +428,8 @@ problem was really in the documentation. Once you've got a precise problem, send e-mail to @email{bug-m4@@gnu.org}. Please include the version number of @code{m4} you are using. You can get this information with the command -@kbd{m4 --version}. You can also run @kbd{make check} to generate the -file @file{tests/@/testsuite.log}, useful for including in your report. +@kbd{m4 --version}. Also provide details about the platform you are +executing on. Non-bug suggestions are always welcome as well. If you have questions about things that are unclear in the documentation or are just obscure @@ -493,8 +467,8 @@ Example of input line The sequence @samp{^D} in an example indicates the end of the input file. The sequence @samp{@key{NL}} refers to the newline character. The majority of these examples are self-contained, and you can run them -with similar results. In fact, the testsuite that is bundled in the -@acronym{GNU} M4 package consists in part of the examples +with similar results by invoking @kbd{m4 -d}. In fact, the testsuite +that is bundled in the GNU M4 package consists of the examples in this document! Some of the examples assume that your current directory is located where you unpacked the installation, so if you plan on following along, you may find it helpful to do this now: @@ -508,35 +482,26 @@ As each of the predefined macros in @code{m4} is described, a prototype call of the macro will be shown, giving descriptive names to the arguments, e.g., -@deffn {Composite (none)} example (@var{string}, @dvar{count, 1}, @ +@deffn Composite example (@var{string}, @dvar{count, 1}, @ @ovar{argument}@dots{}) This is a sample prototype. There is not really a macro named @code{example}, but this documents that if there were, it would be a -Composite macro, rather than a Builtin, and would be provided by the -module @code{none}. - -It requires at least one argument, @var{string}. Remember that in -@code{m4}, there must not be a space between the macro name and the -opening parenthesis, unless it was intended to call the macro without -any arguments. The brackets around @var{count} and @var{argument} show -that these arguments are optional. If @var{count} is omitted, the macro -behaves as if count were @samp{1}, whereas if @var{argument} is omitted, -the macro behaves as if it were the empty string. A blank argument is -not the same as an omitted argument. For example, @samp{example(`a')}, -@samp{example(`a',`1')}, and @samp{example(`a',`1',)} would behave -identically with @var{count} set to @samp{1}; while @samp{example(`a',)} -and @samp{example(`a',`')} would explicitly pass the empty string for -@var{count}. The ellipses (@samp{@dots{}}) show that the macro -processes additional arguments after @var{argument}, rather than -ignoring them. +Composite macro, rather than a Builtin. It requires at least one +argument, @var{string}. Remember that in @code{m4}, there must not be a +space between the macro name and the opening parenthesis, unless it was +intended to call the macro without any arguments. The brackets around +@var{count} and @var{argument} show that these arguments are optional. +If @var{count} is omitted, the macro behaves as if count were @samp{1}, +whereas if @var{argument} is omitted, the macro behaves as if it were +the empty string. A blank argument is not the same as an omitted +argument. For example, @samp{example(`a')}, @samp{example(`a',`1')}, +and @samp{example(`a',`1',)} would behave identically with @var{count} +set to @samp{1}; while @samp{example(`a',)} and @samp{example(`a',`')} +would explicitly pass the empty string for @var{count}. The ellipses +(@samp{@dots{}}) show that the macro processes additional arguments +after @var{argument}, rather than ignoring them. @end deffn -Each builtin definition will list, in parentheses, the module that must -be loaded to use that macro. The standard modules include -@samp{m4} (which is always available), @samp{gnu} (for @acronym{GNU} specific -m4 extensions), and @samp{traditional} (for compatibility with System V -m4). @xref{Modules}. - @cindex numbers All macro arguments in @code{m4} are strings, but some are given special interpretation, e.g., as numbers, file names, regular @@ -569,7 +534,7 @@ The format of the @code{m4} command is: @cindex @env{POSIXLY_CORRECT} All options begin with @samp{-}, or if long option names are used, with @samp{--}. A long option name need not be written completely, any -unambiguous prefix is sufficient. @acronym{POSIX} requires @code{m4} to +unambiguous prefix is sufficient. POSIX requires @code{m4} to recognize arguments intermixed with files, even when @env{POSIXLY_CORRECT} is set in the environment. Most options take effect at startup regardless of their position, but some are documented @@ -582,8 +547,8 @@ into a single command line argument with subsequent options, options with mandatory arguments may be provided either as a single command line argument or as two arguments, and options with optional arguments must be provided as a single argument. In other words, -@kbd{m4 -QPDfoo -d a -d+f} is equivalent to -@kbd{m4 -Q -P -D foo -d ./a -d+f}, although the latter form is +@kbd{m4 -QPDfoo -d a -df} is equivalent to +@kbd{m4 -Q -P -D foo -d -df -- ./a}, although the latter form is considered canonical. With long options, options with mandatory arguments may be provided with @@ -598,7 +563,6 @@ version of @code{m4} introduces an option named @option{--default}). @menu * Operation modes:: Command line options for operation modes -* Dynamic loading features:: Command line options for dynamic loading * Preprocessor features:: Command line options for preprocessor features * Limits control:: Command line options for limits control * Frozen state:: Command line options for frozen state @@ -622,22 +586,6 @@ Print the version number of the program on standard output, then immediately exit @code{m4} without reading any input files or performing any other actions. -@item -b -@itemx --batch -Makes this invocation of @code{m4} non-interactive. This means that -output will be buffered, and an interrupt or pipe write error will halt -execution. If neither -@option{-b} nor @option{-i} are specified, this is activated by default -when any input files are specified, or when either standard input or -standard error is not a terminal. Note that this means that @kbd{m4} -alone might be interactive, but @kbd{m4 -} is not, even though both -commands process only standard input. If both @option{-b} and -@option{-i} are specified, only the last one takes effect. - -@item -c -@itemx --discard-comments -Discard all comments instead of copying them to the output. - @item -E @itemx --fatal-warnings @cindex errors, fatal @@ -651,146 +599,48 @@ a warning is issued. The introduction of behavior levels is new to M4 1.4.9; for behavior consistent with earlier versions, you should specify @option{-E} twice. - -For backwards compatibility reasons, using @option{-E} behaves as if an -implicit @option{--debug=-d} option is also present. This is so that -scripts written for older M4 versions will not fail if they used -constructs that were previously silently allowed, but would now trigger -a warning. - -@example -$ @kbd{m4} -defn(`oops') -@error{}m4:stdin:1: warning: defn: undefined macro `oops' -@result{} -^D -@end example - -@comment ignore -@example -$ @kbd{echo $?} -@result{}0 -@end example - -@comment options: -E -@example -$ @kbd{m4 -E} -defn(`oops') -@result{} -^D -@end example - -@comment ignore -@example -$ @kbd{echo $?} -@result{}0 -@end example - -@comment options: -E -d -@comment status: 1 -@example -$ @kbd{m4 -E -d} -defn(`oops') -@error{}m4:stdin:1: warning: defn: undefined macro `oops' -@result{} -^D -@end example - -@comment ignore -@example -$ @kbd{echo $?} -@result{}1 -@end example - @item -i @itemx --interactive @itemx -e Makes this invocation of @code{m4} interactive. This means that all -output will be unbuffered, interrupts will be ignored, and behavior on -pipe write errors is inherited from the parent process. If neither -@option{-b} nor @option{-i} are specified, this is activated by default -when no input files are specified, and when both standard input and -standard error are terminals (similar to the way that /bin/sh determines -when to be interactive). If both @option{-b} and @option{-i} are -specified, only the last one takes effect. The spelling @option{-e} -exists for compatibility with other @code{m4} implementations, and -issues a warning because it may be withdrawn in a future version of -@acronym{GNU} M4. +output will be unbuffered, and interrupts will be ignored. The +spelling @option{-e} exists for compatibility with other @code{m4} +implementations, and issues a warning because it may be withdrawn in a +future version of GNU M4. @item -P @itemx --prefix-builtins Internally modify @emph{all} builtin macro names so they all start with the prefix @samp{m4_}. For example, using this option, one should write -@samp{m4_define} instead of @samp{define}, and @samp{@w{m4___file__}} -instead of @samp{@w{__file__}}. This option has no effect if @option{-R} +@samp{m4_define} instead of @samp{define}, and @samp{m4___file__} +instead of @samp{__file__}. This option has no effect if @option{-R} is also specified. @item -Q @itemx --quiet @itemx --silent Suppress warnings, such as missing or superfluous arguments in macro -calls, or treating the empty string as zero. Error messages are still -printed. The distinction between error and warning is fuzzy, and if -you encounter a situation where the message output did not match your -expectations, please report that as a bug. This option is implied if -@env{POSIXLY_CORRECT} is set in the environment. - -@item -r@r{[}@var{resyntax-spec}@r{]} -@itemx --regexp-syntax@r{[}=@var{resyntax-spec}@r{]} -Set the regular expression syntax according to @var{resyntax-spec}. -When this option is not given, or @var{resyntax-spec} is omitted, -@acronym{GNU} M4 uses the flavor @code{GNU_M4}, which provides -emacs-compatible regular expressions. @xref{Changeresyntax}, for more -details on the format and meaning of @var{resyntax-spec}. This option -may be given more than once, and order with respect to file names is -significant. - -@item --safer -Cripple the following builtins, since each can perform potentially -unsafe actions: @code{maketemp}, @code{mkstemp} (@pxref{Mkstemp}), -@code{mkdtemp} (@pxref{Mkdtemp}), @code{debugfile} (@pxref{Debugfile}), -@code{syscmd} (@pxref{Syscmd}), and @code{esyscmd} (@pxref{Esyscmd}). -An attempt to use any of these macros will result in an error. This -option is intended to make it safer to preprocess an input file of -unknown origin. - -@item -W -@itemx --warnings -Enable warnings. Warnings are on by default unless -@env{POSIXLY_CORRECT} was set in the environment; this option exists to -allow overriding @option{--silent}. -@comment FIXME should we accept -Wall, -Wnone, -Wcategory, -@comment -Wno-category...? -@end table - -@node Dynamic loading features -@section Command line options for dynamic loading - -On platforms that support dynamic libraries, there are some options -that affect dynamic loading. - -@table @code -@item -M @var{directory} -@itemx --module-directory=@var{directory} -Specify an alternate @var{directory} to search for modules. This option -can be used multiple times to add several different directories to the -module search path. @xref{Modules}, for more details. - -@item -m @var{module} -@itemx --load-module=@var{module} -Load @var{module} before parsing more input files. @var{module} is -searched for in each directory of the module search path, until the -first match is found or the list is exhausted. @xref{Modules}, for more -details. By default, the modules @samp{m4}, @samp{traditional}, and -@samp{gnu} are preloaded, although this can be controlled during -configuration with the @option{--with-modules} option to -@file{m4-@value{VERSION}/@/configure}. This option may be given more -than once, and order with respect to file names is significant. - -@item --unload-module=@var{module} -Unload @var{module} before parsing more input files. @xref{Modules}, -for more details. This option may be given more than once, and order -with respect to file names is significant. +calls, or treating the empty string as zero. + +@item --warn-macro-sequence@r{[}=@var{regexp}@r{]} +Issue a warning if the regular expression @var{regexp} has a non-empty +match in any macro definition (either by @code{define} or +@code{pushdef}). Empty matches are ignored; therefore, supplying the +empty string as @var{regexp} disables any warning. If the optional +@var{regexp} is not supplied, then the default regular expression is +@samp{\$\(@{[^@}]*@}\|[0-9][0-9]+\)} (a literal @samp{$} followed by +multiple digits or by an open brace), since these sequences will +change semantics in the default operation of GNU M4 2.0 (due +to a change in how more than 9 arguments in a macro definition will be +handled, @pxref{Arguments}). Providing an alternate regular +expression can provide a useful reverse lookup feature of finding +where a macro is defined to have a given definition. + +@item -W @var{regexp} +@itemx --word-regexp=@var{regexp} +Use @var{regexp} as an alternative syntax for macro names. This +experimental option will not be present in all GNU @code{m4} +implementations (@pxref{Changeword}). @end table @node Preprocessor features @@ -805,19 +655,6 @@ search path can be altered, and the output file can track where the input came from. These features occur with the following options: @table @code -@item -B @var{directory} -@itemx --prepend-include=@var{directory} -Make @code{m4} search @var{directory} for included files, prior to -searching the current working directory. @xref{Search Path}, for more -details. This option may be given more than once. Some other -implementations of @code{m4} use @option{-B @var{number}} to change their -hard-coded limits, but that is unnecessary in @acronym{GNU} where the -only limit is your hardware capability. So although it is unlikely that -you will want to include a relative directory whose name is purely -numeric, @acronym{GNU} @code{m4} will warn you about this potential -compatibility issue; you can avoid the warning by using the long -spelling, or by using @samp{./@var{number}} if you really meant it. - @item -D @var{name}@r{[}=@var{value}@r{]} @itemx --define=@var{name}@r{[}=@var{value}@r{]} This enters @var{name} into the symbol table. If @samp{=@var{value}} is @@ -827,44 +664,18 @@ if it was defined from within the input. This option may be given more than once; order with respect to file names is significant, and redefining the same @var{name} loses the previous value. -@item --import-environment -Imports every variable in the environment as a macro. This is done -before @option{-D} and @option{-U}, so they can override the -environment. - @item -I @var{directory} @itemx --include=@var{directory} Make @code{m4} search @var{directory} for included files that are not found in the current working directory. @xref{Search Path}, for more details. This option may be given more than once. -@item --popdef=@var{name} -This deletes the top-most meaning @var{name} might have. Obviously, -only predefined macros can be deleted in this way. This option may be -given more than once; popping a @var{name} that does not have a -definition is silently ignored. Order is significant with respect to -file names. - -@item -p @var{name}@r{[}=@var{value}@r{]} -@itemx --pushdef=@var{name}@r{[}=@var{value}@r{]} -This enters @var{name} into the symbol table. If @samp{=@var{value}} is -missing, the value is taken to be the empty string. The @var{value} can -be any string, and the macro can be defined to take arguments, just as -if it was defined from within the input. This option may be given more -than once; order with respect to file names is significant, and -redefining the same @var{name} adds another definition to its stack. - @item -s @itemx --synclines -Short for @option{--syncoutput=1}, turning on synchronization lines -(sometimes called @dfn{synclines}). - -@item --syncoutput@r{[}=@var{state}@r{]} @cindex synchronization lines @cindex location, input @cindex input location -Control the generation of synchronization lines from the command line. -Synchronization lines are for use by the C preprocessor or other +Generate synchronization lines, for use by the C preprocessor or other similar tools. Order is significant with respect to file names. This option is useful, for example, when @code{m4} is used as a front end to a compiler. Source file name and line number information @@ -879,10 +690,41 @@ Synchronization directives are always given on complete lines by themselves. When a synchronization discrepancy occurs in the middle of an output line, the associated synchronization directive is delayed until the next newline that does not occur in the middle of a quoted -string or comment. @xref{Syncoutput}, for runtime control. @var{state} -is interpreted the same as the argument to @code{syncoutput}; if -@var{state} is omitted, or @option{--syncoutput} is not used, -synchronization lines are disabled. +string or comment. + +@comment options: -s +@example +define(`twoline', `1 +2') +@result{}#line 2 "stdin" +@result{} +changecom(`/*', `*/') +@result{} +define(`comment', `/*1 +2*/') +@result{}#line 5 +@result{} +dnl no line +hello +@result{}#line 7 +@result{}hello +twoline +@result{}1 +@result{}#line 8 +@result{}2 +comment +@result{}/*1 +@result{}2*/ +one comment `two +three' +@result{}#line 10 +@result{}one /*1 +@result{}2*/ two +@result{}three +goodbye +@result{}#line 12 +@result{}goodbye +@end example @item -U @var{name} @itemx --undefine=@var{name} @@ -899,23 +741,38 @@ file names. There are some limits within @code{m4} that can be tuned. For compatibility, @code{m4} also accepts some options that control limits in other implementations, but which are automatically unbounded (limited -only by your hardware and operating system constraints) in @acronym{GNU} +only by your hardware and operating system constraints) in GNU @code{m4}. @table @code @item -g @itemx --gnu -Enable all the extensions in this implementation. This is on by -default unless @env{POSIXLY_CORRECT} is set in the environment; it -exists to allow overriding @option{--traditional}. +Enable all the extensions in this implementation. In this release of +M4, this option is always on by default; it is currently only useful +when overriding a prior use of @option{--traditional}. However, having +GNU behavior as default makes it impossible to write a +strictly POSIX-compliant client that avoids all incompatible +GNU M4 extensions, since such a client would have to use the +non-POSIX command-line option to force full POSIX +behavior. Thus, a future version of M4 will be changed to implicitly +use the option @option{--traditional} if the environment variable +@env{POSIXLY_CORRECT} is set. Projects that intentionally use +GNU extensions should consider using @option{--gnu} to state +their intentions, so that the project will not mysteriously break if the +user upgrades to a newer M4 and has @env{POSIXLY_CORRECT} set in their +environment. @item -G -@itemx --posix @itemx --traditional Suppress all the extensions made in this implementation, compared to the -System V version. @xref{Compatibility}, for a list of these. This -loads the @samp{traditional} module in place of the @samp{gnu} module. -It is implied if @env{POSIXLY_CORRECT} is set in the environment. +System V version. @xref{Compatibility}, for a list of these. + +@item -H @var{num} +@itemx --hashsize=@var{num} +Make the internal hash table for symbol lookup be @var{num} entries big. +For better performance, the number should be prime, but this is not +checked. The default is 509 entries. It should not be necessary to +increase this value, unless you define an excessive number of macros. @item -L @var{num} @itemx --nesting-limit=@var{num} @@ -923,19 +780,16 @@ It is implied if @env{POSIXLY_CORRECT} is set in the environment. @cindex limit, nesting Artificially limit the nesting of macro calls to @var{num} levels, stopping program execution if this limit is ever exceeded. When not -specified, nesting is limited to 1024 levels. A value of zero means +specified, nesting defaults to unlimited on platforms that can detect +stack overflow, and to 1024 levels otherwise. A value of zero means unlimited; but then heavily nested code could potentially cause a stack -overflow. @var{num} can have an optional scaling suffix. -@comment FIXME - need a node on what scaling suffixes are supported (see -@comment [info coreutils 'block size'] for ideas), and need to consider -@comment whether builtins should also understand scaling suffixes: -@comment eval, mpeval, perhaps format +overflow. -The precise effect of this option might be more correctly associated +The precise effect of this option is more correctly associated with textual nesting than dynamic recursion. It has been useful -when some complex @code{m4} input was generated by mechanical means. -Most users would never need this option. If shown to be obtrusive, -this option (which is still experimental) might well disappear. +when some complex @code{m4} input was generated by mechanical means, and +also in diagnosing recursive algorithms that do not scale well. +Most users never need to change this option from its default. @cindex rescanning This option does @emph{not} have the ability to break endless @@ -944,32 +798,31 @@ or stack space. Through clever usage of rescanning loops, one can request complex, time-consuming computations from @code{m4} with useful results. Putting limitations in this area would break @code{m4} power. There are many pathological cases: @w{@samp{define(`a', `a')a}} is -only the simplest example (but @pxref{Compatibility}). Expecting @acronym{GNU} +only the simplest example (but @pxref{Compatibility}). Expecting GNU @code{m4} to detect these would be a little like expecting a compiler system to detect and diagnose endless loops: it is a quite @emph{hard} problem in general, if not undecidable! -@item -H @var{num} -@itemx --hashsize=@var{num} -@itemx --word-regexp=@var{regexp} -These options are present only for compatibility with previous versions -of GNU @code{m4}. They do nothing except issue a warning, because the -symbol table size is not fixed anymore, and because the new -@code{changesyntax} feature is more efficient than the withdrawn -experimental @code{changeword}. These options will eventually disappear -in future releases. - -@item -S @var{num} +@item -B @var{num} +@itemx -S @var{num} @itemx -T @var{num} These options are present for compatibility with System V @code{m4}, but do nothing in this implementation. They may disappear in future releases, and issue a warning to that effect. + +@item -N @var{num} +@itemx --diversions=@var{num} +These options are present only for compatibility with previous +versions of GNU @code{m4}, and were controlling the number of +possible diversions which could be used at the same time. They do nothing, +because there is no fixed limit anymore. They may disappear in future +releases, and issue a warning to that effect. @end table @node Frozen state @section Command line options for frozen state -@acronym{GNU} @code{m4} comes with a feature of freezing internal state +GNU @code{m4} comes with a feature of freezing internal state (@pxref{Frozen files}). This can be used to speed up @code{m4} execution when reusing a common initialization script. @@ -983,9 +836,9 @@ in @samp{.m4f}. @item -R @var{file} @itemx --reload-state=@var{file} Before execution starts, recover the internal state from the specified -frozen @var{file}. The options @option{-D}, @option{-U}, @option{-t}, -@option{-m}, @option{-r}, and @option{--import-environment} take effect -after state is reloaded, but before the input files are read. +frozen @var{file}. The options @option{-D}, @option{-U}, and +@option{-t} take effect after state is reloaded, but before the input +files are read. @end table @node Debugging options @@ -995,84 +848,58 @@ Finally, there are several options for aiding in debugging @code{m4} scripts. @table @code -@item -d@r{[}@r{[}-@r{|}+@r{]}@var{flags}@r{]} -@itemx --debug@r{[}=@r{[}-@r{|}+@r{]}@var{flags}@r{]} -@itemx --debugmode@r{[}=@r{[}-@r{|}+@r{]}@var{flags}@r{]} +@item -d@r{[}@var{flags}@r{]} +@itemx --debug@r{[}=@var{flags}@r{]} Set the debug-level according to the flags @var{flags}. The debug-level controls the format and amount of information presented by the debugging -functions. @xref{Debugmode}, for more details on the format and -meaning of @var{flags}. If omitted, @var{flags} defaults to -@samp{+adeq}. If the option occurs multiple times, @var{flags} starting -with @samp{-} or @samp{+} are cumulative, while @var{flags} starting -with a letter override all earlier settings. The debug-level starts -with @samp{d} enabled and all other flags disabled. To disable all -previously set flags, specify an explicit @var{flags} of @samp{-V}. For -backward compatibility reasons, the option @option{--fatal-warnings} -implies @samp{--debug=-d} as part of its effects. The spelling -@option{--debug} is recognized as an unambiguous option for -compatibility with earlier versions of @acronym{GNU} M4, but for -consistency with the builtin name, you can also use the spelling -@option{--debugmode}. Order is significant with respect to file names. - -The cumulative effect of the various options in this example is -equivalent to a single invocation of @code{debugmode(`adlqx')}: - -@comment options: -d-V -d+lx --debug --debugmode=-e -@example -$ @kbd{m4 -d+lx --debug --debugmode=-e} -traceon(`len') -@result{} -len(`123') -@error{}m4trace:2: -1- id 2: len(`123') -@result{}3 -@end example +functions. @xref{Debug Levels}, for more details on the format and +meaning of @var{flags}. If omitted, @var{flags} defaults to @samp{aeq}. @item --debugfile@r{[}=@var{file}@r{]} @itemx -o @var{file} @itemx --error-output=@var{file} -Redirect debug messages and trace output to the +Redirect @code{dumpdef} output, debug messages, and trace output to the named @var{file}. Warnings, error messages, and @code{errprint} output -are still printed to standard error. Output from @code{dumpdef} goes to -this file when the debug level @code{o} is not set (@pxref{Debugmode}). -If these options are not used, or +are still printed to standard error. If these options are not used, or if @var{file} is unspecified (only possible for @option{--debugfile}), debug output goes to standard error; if @var{file} is the empty string, -debug output is discarded. @xref{Debugfile}, for more details. The +debug output is discarded. @xref{Debug Output}, for more details. The option @option{--debugfile} may be given more than once, and order is significant with respect to file names. The spellings @option{-o} and -@option{--error-output} are misleading and -inconsistent with other @acronym{GNU} tools; using those spellings will -evoke a warning, and they may be withdrawn or change semantics in a -future release. +@option{--error-output} are misleading and inconsistent with other +GNU tools; for now they are silently accepted as synonyms of +@option{--debugfile} and only recognized once, but in a future version +of M4, using them will cause a warning to be issued. + +@ignore +@comment not worth including in the manual, but provides a good test + +@comment examples +@comment options: -Dbar=hello -tbar --debugfile= foo --debugfile - +@example +$ @kbd{m4 -d -Iexamples -Dbar=hello -tbar --debugfile= foo --debugfile - +@result{}hello +errprint(`hi +')dnl +@error{}hi +bar +@error{}m4trace: -1- bar -> `hello' +@result{}hello +@end example +@end ignore @item -l @var{num} -@itemx --debuglen=@var{num} @itemx --arglength=@var{num} -Restrict the size of the output generated by macro tracing or by -@code{dumpdef} to @var{num} characters per string. If unspecified or -zero, output is unlimited. @xref{Debuglen}, for more details. -@var{num} can have an optional scaling suffix. The spelling -@option{--arglength} is deprecated, since it does not match the -@code{debuglen} macro; using it will evoke a warning, and it may be -withdrawn in a future release. -@comment FIXME - Should we add an option that controls whether output -@comment strings are sanitized with escape sequences, so that dumpdef is -@comment truly one line per macro? -@comment FIXME - see comment on --nesting-limit about NUM. +Restrict the size of the output generated by macro tracing to @var{num} +characters per trace line. If unspecified or zero, output is +unlimited. @xref{Debug Levels}, for more details. @item -t @var{name} @itemx --trace=@var{name} -@itemx --traceon=@var{name} This enables tracing for the macro @var{name}, at any point where it is defined. @var{name} need not be defined when this option is given. This option may be given more than once, and order is significant with respect to file names. @xref{Trace}, for more details. - -@item --traceoff=@var{name} -This disables tracing for the macro @var{name}, at any point where it is -defined. @var{name} need not be defined when this option is given. -This option may be given more than once, and order is significant with -respect to file names. @xref{Trace}, for more details. @end table @node Command line files @@ -1091,19 +918,14 @@ on the command line; this makes a difference when input is from a terminal or other special file type. It is an error if an input file ends in the middle of argument collection, a comment, or a quoted string. -@comment FIXME - it would be nicer if we let these three things -@comment continue across file boundaries, provided that we warn in -@comment interactive use when switching to stdin in a non-default parse -@comment state. -Various options, such as @option{--define} (@option{-D}), @option{--undefine} -(@option{-U}), @option{--synclines} (@option{-s}), @option{--trace} -(@option{-t}), @option{--regexp-syntax} (@option{-r}), and -@option{--load-module} (@option{-m}), only take effect after processing -input from any file names that occur earlier on the command line. For -example, assume the file @file{foo} contains: +The options @option{--define} (@option{-D}), @option{--undefine} +(@option{-U}), @option{--synclines} (@option{-s}), and @option{--trace} +(@option{-t}) only take effect after processing input from any file +names that occur earlier on the command line. For example, assume the +file @file{foo} contains: -@comment file: foo +@comment ignore @example $ @kbd{cat foo} bar @@ -1128,6 +950,64 @@ If you need to read a file whose name starts with a @file{-}, you can specify it as @samp{./-file}, or use @option{--} to mark the end of options. +@ignore +@comment Test that 'm4 file/' detects that file is not a directory; we +@comment can assume that the current directory contains a Makefile. +@comment mingw fails with EINVAL rather than ENOTDIR. + +@comment status: 1 +@comment xerr: ignore +@comment options: Makefile/ +@example +@error{}m4: cannot open `Makefile/': Not a directory +@end example + +@comment Test that closed stderr does not cause a crash. Not all +@comment systems have the same message for EBADF. + +@comment xerr: ignore +@example +ifdef(`__unix__', , + `errprint(` skipping: syscmd does not have unix semantics +')m4exit(`77')')dnl +changequote(`[', `]')dnl +syscmd([echo | ']__program__[' >&-])dnl +@error{}m4: write error: Bad file descriptor +sysval +@result{}1 +@end example + +@example +ifdef(`__unix__', , + `errprint(` skipping: syscmd does not have unix semantics +')m4exit(`77')')dnl +changequote(`[', `]')dnl +syscmd([echo 'esyscmd(echo hi >&2 && echo err"print(bye +)d"nl)dnl' > tmp.m4 \ + && ']__program__[' tmp.m4 <&- >&- \ + && rm tmp.m4])sysval +@error{}hi +@error{}bye +@result{}0 +@end example + +@comment Test that we obey POSIX semantics with -D interspersed with +@comment files, even with POSIXLY_CORRECT (BSD getopt gets it wrong). + +$ @kbd{m4 } +@example +ifdef(`__unix__', , + `errprint(` skipping: syscmd does not have unix semantics +')m4exit(`77')')dnl +changequote(`[', `]')dnl +syscmd([POSIXLY_CORRECT=1 ']__program__[' -Dbar=hello foo -Dbar=world foo])dnl +@result{}hello +@result{}world +sysval +@result{}0 +@end example +@end ignore + @node Syntax @chapter Lexical and syntactic conventions @@ -1136,7 +1016,7 @@ options. As @code{m4} reads its input, it separates it into @dfn{tokens}. A token is either a name, a quoted string, or any single character, that is not a part of either a name or a string. Input to @code{m4} can also -contain comments. @acronym{GNU} @code{m4} does not yet understand +contain comments. GNU @code{m4} does not yet understand multibyte locales; all operations are byte-oriented rather than character-oriented (although if your locale uses a single byte encoding, such as @sc{ISO-8859-1}, you will not notice a difference). @@ -1145,17 +1025,12 @@ use non-@sc{ascii} characters in quoted strings (@pxref{Changequote}), comments (@pxref{Changecom}), and macro names (@pxref{Indir}), with the exception of the @sc{nul} character (the zero byte @samp{'\0'}). -@comment FIXME - each builtin needs to document how it handles NUL, then -@comment update the above paragraph to mention that NUL is now handled -@comment transparently. - @menu * Names:: Macro names * Quoted strings:: Quoting input to @code{m4} * Comments:: Comments in @code{m4} input * Other tokens:: Other kinds of input tokens * Input processing:: How @code{m4} copies input to output -* Regular expression syntax:: How @code{m4} interprets regular expressions @end menu @node Names @@ -1171,10 +1046,6 @@ macro definition, it will be subject to macro expansion Examples of legal names are: @samp{foo}, @samp{_tmp}, and @samp{name01}. -The definitions of letters, digits and other input characters can be -changed at any time, using the builtin macro @code{changesyntax}. -@xref{Changesyntax}, for more information. - @node Quoted strings @section Quoting input to @code{m4} @@ -1182,9 +1053,7 @@ changed at any time, using the builtin macro @code{changesyntax}. @cindex string, quoted A quoted string is a sequence of characters surrounded by quote strings, defaulting to -@samp{`} (grave-accent, also known as back-tick, with UCS value U0060) -and @samp{'} (apostrophe, also known as single-quote, with UCS value -U0027), where the nested begin and end quotes within the +@samp{`} and @samp{'}, where the nested begin and end quotes within the string are balanced. The value of a string token is the text, with one level of quotes stripped off. Thus @@ -1203,9 +1072,8 @@ is the empty string, and double-quoting turns into single-quoting. @result{}`quoted' @end example -The quote characters can be changed at any time, using the builtin macros -@code{changequote} (@pxref{Changequote}) or @code{changesyntax} -(@pxref{Changesyntax}). +The quote characters can be changed at any time, using the builtin macro +@code{changequote}. @xref{Changequote}, for more information. @node Comments @section Comments in @code{m4} input @@ -1214,10 +1082,7 @@ The quote characters can be changed at any time, using the builtin macros Comments in @code{m4} are normally delimited by the characters @samp{#} and newline. All characters between the comment delimiters are ignored, but the entire comment (including the delimiters) is passed through to -the output, unless you supply the @option{--discard-comments} or -@option{-c} option at the command line (@pxref{Operation modes, , -Invoking m4}). When discarding comments, the comment delimiters are -discarded, even if the close-comment string is a newline. +the output---comments are @emph{not} discarded by @code{m4}. Comments cannot be nested, so the first newline after a @samp{#} ends the comment. The commenting effect of the begin-comment string @@ -1231,17 +1096,30 @@ $ @kbd{m4} @result{}quoting inhibits # comments @end example -@comment options: -c +The comment delimiters can be changed to any string at any time, using +the builtin macro @code{changecom}. @xref{Changecom}, for more +information. + +@ignore +@comment Detect regression in 1.4.10b in regards to reparsing comments. +@comment Not worth including in the manual. @example -$ @kbd{m4 -c} -`quoted text' # `commented text' -`quoting inhibits' `#' `comments' -@result{}quoted text quoting inhibits # comments +define(`e', `$@@')define(`q', ``$@@'')define(`foo', `bar') +@result{} +q(e(`one +',#two ' foo +)) +@result{}`one +@result{}',`#two bar +@result{}'' +changecom(`<', `>')define(`n', `$#') +@result{} +n(e(<`>, <'>)) +@result{}1 +len(e(<`>, ,<'>)) +@result{}12 @end example - -The comment delimiters can be changed to any string at any time, using -the builtin macros @code{changecom} (@pxref{Changecom}) or -@code{changesyntax} (@pxref{Changesyntax}). +@end ignore @node Other tokens @section Other kinds of input tokens @@ -1253,8 +1131,7 @@ expansion, all of these tokens are just copied to output. However, during macro expansion, whitespace characters (space, tab, newline, formfeed, carriage return, vertical tab), parentheses (@samp{(} and @samp{)}), comma (@samp{,}), and dollar (@samp{$}) have additional -roles, explained later. Which characters actually perform these roles -can be adjusted with @code{changesyntax} (@pxref{Changesyntax}). +roles, explained later. @node Input processing @section How @code{m4} copies input to output @@ -1308,8 +1185,8 @@ round of scanning for the tokens @samp{Result}, @samp{@w{ }}, @result{}Result is 32768 @end example -As a more complicated example, we will contrast an actual code example -from the Gnulib project@footnote{Derived from a patch in +As a more complicated example, we will contrast an actual code +example from the Gnulib project@footnote{Derived from a patch in @uref{http://lists.gnu.org/archive/html/bug-gnulib/@/2007-01/@/msg00389.html}, and a followup patch in @uref{http://lists.gnu.org/archive/html/bug-gnulib/@/2007-02/@/msg00000.html}}, @@ -1438,16 +1315,7 @@ end of output is the literal @samp{@key{NL}} that appeared after the invocation of the macro. The order in which @code{m4} expands the macros can be further explored -using the trace facilities of @acronym{GNU} @code{m4} (@pxref{Trace}). - -@node Regular expression syntax -@section How @code{m4} interprets regular expressions - -There are several contexts where @code{m4} parses an argument as a -regular expression. This section describes the various flavors of -regular expressions. @xref{Changeresyntax}. - -@include regexprops-generic.texi +using the trace facilities of GNU @code{m4} (@pxref{Trace}). @node Macros @chapter How to invoke macros @@ -1511,22 +1379,22 @@ An innovation of the @code{m4} language, compared to some of its predecessors (like Strachey's @code{GPM}, for example), is the ability to recognize macro calls without resorting to any special, prefixed invocation character. While generally useful, this feature might -sometimes be the source of spurious, unwanted macro calls. So, @acronym{GNU} +sometimes be the source of spurious, unwanted macro calls. So, GNU @code{m4} offers several mechanisms or techniques for inhibiting the recognition of names as macro calls. -@cindex @acronym{GNU} extensions +@cindex GNU extensions @cindex blind macro @cindex macro, blind First of all, many builtin macros cannot meaningfully be called without -arguments. As a @acronym{GNU} extension, for any of these macros, +arguments. As a GNU extension, for any of these macros, whenever an opening parenthesis does not immediately follow their name, the builtin macro call is not triggered. This solves the most usual cases, like for @samp{include} or @samp{eval}. Later in this document, the sentence ``This macro is recognized only with parameters'' refers to -this specific provision of @acronym{GNU} M4, also known as a blind -builtin macro. For the builtins defined by @acronym{POSIX} that bear -this disclaimer, @acronym{POSIX} specifically states that invoking those +this specific provision of GNU M4, also known as a blind +builtin macro. For the builtins defined by POSIX that bear +this disclaimer, POSIX specifically states that invoking those builtins without arguments is unspecified, because many other implementations simply invoke the builtin as though it were given one empty argument instead. @@ -1560,9 +1428,12 @@ m4_eval(`1') @end example Another alternative is to redefine problematic macros to a name less -likely to cause conflicts, @xref{Definitions}. Or the parsing engine -can be changed to redefine what constitutes a valid macro name, -@xref{Changesyntax}. +likely to cause conflicts, @xref{Definitions}. + +If your version of GNU @code{m4} has the @code{changeword} feature +compiled in, it offers far more flexibility in specifying the +syntax of macro names, both builtin or user-defined. @xref{Changeword}, +for more information on this experimental feature. Of course, the simplest way to prevent a name from being interpreted as a call to an existing macro is to quote it. The remainder of @@ -1617,6 +1488,19 @@ x`'y @result{}bCD @end example +@ignore +@comment Similar, but with argument references, to ensure good test +@comment coverage. +@example +define(`x1', `len(`$1'') +@result{} +define(`y1', ``$1')') +@result{} +x1(`01234567890123456789')y1(`98765432109876543210') +@result{}40 +@end example +@end ignore + Unquoted strings on either side of a quoted string are subject to being recognized as macro names. In the following example, quoting the empty string allows for the second @code{macro} to be recognized as such: @@ -1696,12 +1580,12 @@ defined macros, there is no check of the number of arguments given. @example $ @kbd{m4} index(`abc') -@error{}m4:stdin:1: warning: index: too few arguments: 1 < 2 +@error{}m4:stdin:1: Warning: too few arguments to builtin `index' @result{}0 index(`abc',) @result{}0 -index(`abc', `b', `0', `ignored') -@error{}m4:stdin:3: warning: index: extra arguments ignored: 4 > 3 +index(`abc', `b', `ignored') +@error{}m4:stdin:3: Warning: excess arguments to builtin `index' ignored @result{}1 @end example @@ -1712,7 +1596,7 @@ index(`abc') @result{}0 index(`abc',) @result{}0 -index(`abc', `b', `', `ignored') +index(`abc', `b', `ignored') @result{}1 @end example @@ -1753,7 +1637,7 @@ hello world @result{}hello world define( ^D -@error{}m4:stdin:2: define: end of file in argument list +@error{}m4:stdin:2: ERROR: end of file in argument list @end example @node Quoting Arguments @@ -1797,7 +1681,7 @@ For consistency, this manual follows the rule of thumb that each layer of parentheses introduces another layer of single quoting, except when showing the consequences of quoting rules. This is done even when the quoted string cannot be a macro, such as with integers when you have not -changed the syntax via @code{changesyntax} (@pxref{Changesyntax}). +changed the syntax via @code{changeword} (@pxref{Changeword}). The quoting rule of thumb of one level of quoting per parentheses has a nice property: when a macro name appears inside parentheses, you can @@ -1832,18 +1716,34 @@ therefore result in more macros being called, if the calls are included, completely or partially, in the first macro calls' expansion. Taking a very simple example, if @var{foo} expands to @samp{bar}, and -@var{bar} expands to @samp{Hello world}, the input +@var{bar} expands to @samp{Hello}, the input -@comment options: -Dbar='Hello world' -Dfoo=bar +@comment options: -Dbar=Hello -Dfoo=bar @example -$ @kbd{m4 -Dbar="Hello world" -Dfoo=bar} +$ @kbd{m4 -Dbar=Hello -Dfoo=bar} foo -@result{}Hello world +@result{}Hello @end example @noindent will expand first to @samp{bar}, and when this is reread and -expanded, into @samp{Hello world}. +expanded, into @samp{Hello}. + +@ignore +@comment not worth documenting, but test that the command line can +@comment define macros that take parameters + +@comment options: -Dfoo -Decho=$@ +@example +$ @kbd{m4 -Dfoo -Decho='$@'} +foo +@result{} +foo(`silently ignored') +@result{} +echo(`1', `2') +@result{}1,2 +@end example +@end ignore @node Definitions @chapter How to define new macros @@ -1861,11 +1761,9 @@ value, and bring back the original value at a later time. * Undefine:: Deleting a macro * Defn:: Renaming macros * Pushdef:: Temporarily redefining macros -* Renamesyms:: Renaming macros with regular expressions * Indir:: Indirect call of macros * Builtin:: Indirect call of builtins -* M4symbols:: Getting the defined macro names @end menu @node Define @@ -1874,30 +1772,13 @@ value, and bring back the original value at a later time. The normal way to define or redefine macros is to use the builtin @code{define}: -@deffn {Builtin (m4)} define (@var{name}, @ovar{expansion}) +@deffn Builtin define (@var{name}, @ovar{expansion}) Defines @var{name} to expand to @var{expansion}. If @var{expansion} is not given, it is taken to be empty. The expansion of @code{define} is void. The macro @code{define} is recognized only with parameters. @end deffn -@comment Other implementations, such as Solaris, can define a macro -@comment with a builtin token attached to text: -@comment define(foo, a`'defn(`divnum')b) -@comment defn(`foo') => ab -@comment dumpdef(`foo') => foo: a<divnum>b -@comment len(defn(`foo')) => 3 -@comment index(defn(`foo'), defn(`divnum')) => 1 -@comment foo => a0b -@comment It may be worth making some changes to support this behavior, -@comment or something similar to it. -@comment -@comment But be sure it has sane semantics, with potentially deferred -@comment expansion of builtins. For example, this should not warn -@comment about trying to access the definition of an undefined macro: -@comment define(`foo', `ifdef(`$1', 'defn(`defn')`)')foo(`oops') -@comment Also, think how to handle conflicting argument counts: -@comment define(`bar', defn(`dnl', `len')) The following example defines the macro @var{foo} to expand to the text @samp{Hello World.}. @@ -1928,19 +1809,19 @@ one @result{}two @end example -@cindex @acronym{GNU} extensions -@acronym{GNU} @code{m4} normally replaces only the @emph{topmost} +@cindex GNU extensions +GNU @code{m4} normally replaces only the @emph{topmost} definition of a macro if it has several definitions from @code{pushdef} (@pxref{Pushdef}). Some other implementations of @code{m4} replace all definitions of a macro with @code{define}. @xref{Incompatibilities}, for more details. -As a @acronym{GNU} extension, the first argument to @code{define} does +As a GNU extension, the first argument to @code{define} does not have to be a simple word. It can be any text string, even the empty string. A macro with a non-standard name cannot be invoked in the normal way, as the name is -not recognized. It can only be referenced by the builtins @code{Indir} -(@pxref{Indir}) and @code{Defn} (@pxref{Defn}). +not recognized. It can only be referenced by the builtins @code{indir} +(@pxref{Indir}) and @code{defn} (@pxref{Defn}). @cindex arrays Arrays and associative arrays can be simulated by using non-standard @@ -2010,20 +1891,6 @@ macro (You should try and improve this example so that clients of @code{exch} do not have to double quote; or @pxref{Improved exch, , Answers}). -@cindex @acronym{GNU} extensions -@acronym{GNU} @code{m4} allows the number following the @samp{$} to -consist of one -or more digits, allowing macros to have any number of arguments. This -is not so in UNIX implementations of @code{m4}, which only recognize -one digit. -@comment FIXME - See Austin group XCU ERN 111. POSIX says that $11 must -@comment be the first argument concatenated with 1, and instead reserves -@comment ${11} for implementation use. Once this is implemented, the -@comment documentation needs to reflect how these extended arguments -@comment are handled, as well as backwards compatibility issues with -@comment 1.4.x. Also, consider adding further extensions such as -@comment ${1-default}, which expands to `default' if $1 is empty. - As a special case, the zeroth argument, @code{$0}, is always the name of the macro being expanded. @@ -2048,6 +1915,62 @@ foo The @samp{foo} in the expansion text is @emph{not} expanded, since it is a quoted string, and not a name. +@cindex GNU extensions +@cindex nine arguments, more than +@cindex more than nine arguments +@cindex arguments, more than nine +@cindex positional parameters, more than nine +GNU @code{m4} allows the number following the @samp{$} to +consist of one or more digits, allowing macros to have any number of +arguments. The extension of accepting multiple digits is incompatible +with POSIX, and is different than traditional implementations +of @code{m4}, which only recognize one digit. Therefore, future +versions of GNU M4 will phase out this feature. To portably +access beyond the ninth argument, you can use the @code{argn} macro +documented later (@pxref{Shift}). + +POSIX also states that @samp{$} followed immediately by +@samp{@{} in a macro definition is implementation-defined. This version +of M4 passes the literal characters @samp{$@{} through unchanged, but M4 +2.0 will implement an optional feature similar to @command{sh}, where +@samp{$@{11@}} expands to the eleventh argument, to replace the current +recognition of @samp{$11}. Meanwhile, if you want to guarantee that you +will get a literal @samp{$@{} in output when expanding a macro, even +when you upgrade to M4 2.0, you can use nested quoting to your +advantage: + +@example +define(`foo', `single quoted $`'@{1@} output') +@result{} +define(`bar', ``double quoted $'`@{2@} output'') +@result{} +foo(`a', `b') +@result{}single quoted $@{1@} output +bar(`a', `b') +@result{}double quoted $@{2@} output +@end example + +To help you detect places in your M4 input files that might change in +behavior due to the changed behavior of M4 2.0, you can use the +@option{--warn-macro-sequence} command-line option (@pxref{Operation +modes, , Invoking m4}) with the default regular expression. This will +add a warning any time a macro definition includes @samp{$} followed by +multiple digits, or by @samp{@{}. The warning is not enabled by +default, because it triggers a number of warnings in Autoconf 2.61 (and +Autoconf uses @option{-E} to treat warnings as errors), and because it +will still be possible to restore older behavior in M4 2.0. + +@comment options: --warn-macro-sequence +@example +$ @kbd{m4 --warn-macro-sequence} +define(`foo', `$001 $@{1@} $1') +@error{}m4:stdin:1: Warning: definition of `foo' contains sequence `$001' +@error{}m4:stdin:1: Warning: definition of `foo' contains sequence `$@{1@}' +@result{} +foo(`bar') +@result{}bar $@{1@} bar +@end example + @node Pseudo Arguments @section Special arguments to macros @@ -2159,6 +2082,35 @@ foo) @result{}bar' @end example +@ignore +@comment Not worth putting in the manual, but this example is needed for +@comment good test coverage of copying large strings across recursion +@comment levels. + +@example +define(`echo', `$@@')dnl +echo(echo(`01234567890123456789', `01234567890123456789') +echo(`98765432109876543210', `98765432109876543210')) +@result{}01234567890123456789,01234567890123456789 +@result{}98765432109876543210,98765432109876543210 +len((echo(`01234567890123456789', + `01234567890123456789')echo(`98765432109876543210', + `98765432109876543210'))) +@result{}84 +indir(`echo', indir(`echo', `01234567890123456789', + `01234567890123456789') +indir(`echo', `98765432109876543210', `98765432109876543210')) +@result{}01234567890123456789,01234567890123456789 +@result{}98765432109876543210,98765432109876543210 +define(`argn', `$#')dnl +define(`echo1', `-$@@-')define(`echo2', `,$@@,')dnl +echo1(`1', `2', `3') argn(echo1(`1', `2', `3')) +@result{}-1,2,3- 3 +echo2(`1', `2', `3') argn(echo2(`1', `2', `3')) +@result{},1,2,3, 5 +@end example +@end ignore + A @samp{$} sign in the expansion text, that is not followed by anything @code{m4} understands, is simply copied to the macro expansion, as any other text is. @@ -2210,11 +2162,9 @@ foo(`arg') @cindex undefining macros A macro definition can be removed with @code{undefine}: -@deffn {Builtin (m4)} undefine (@var{name}@dots{}) +@deffn Builtin undefine (@var{name}@dots{}) For each argument, remove the macro @var{name}. The macro names must -necessarily be quoted, since they will be expanded otherwise. If an -argument is not a defined macro, then the @samp{d} debug level controls -whether a warning is issued (@pxref{Debugmode}). +necessarily be quoted, since they will be expanded otherwise. The expansion of @code{undefine} is void. The macro @code{undefine} is recognized only with parameters. @@ -2249,21 +2199,8 @@ f(`bye') @result{}f(bye) @end example -As of M4 1.6, @code{undefine} can warn if @var{name} is not a macro, by -using @code{debugmode} (@pxref{Debugmode}) or the command line option -@option{-d} (@option{--debugmode}, @pxref{Debugging options, , Invoking -m4}). - -@example -$ @kbd{m4} -undefine(`a') -@error{}m4:stdin:1: warning: undefine: undefined macro `a' -@result{} -debugmode(`-d') -@result{} -undefine(`a') -@result{} -@end example +It is not an error for @var{name} to have no macro definition. In that +case, @code{undefine} does nothing. @node Defn @section Renaming macros @@ -2275,18 +2212,20 @@ undefine(`a') It is possible to rename an already defined macro. To do this, you need the builtin @code{defn}: -@deffn {Builtin (m4)} defn (@var{name}@dots{}) +@deffn Builtin defn (@var{name}@dots{}) Expands to the @emph{quoted definition} of each @var{name}. If an argument is not a defined macro, the expansion for that argument is -empty, and the @samp{d} debug level controls whether a warning is issued -(@pxref{Debugmode}). +empty. If @var{name} is a user-defined macro, the quoted definition is simply -the quoted expansion text. If, instead, @var{name} is a builtin, the +the quoted expansion text. If, instead, there is only one @var{name} +and it is a builtin, the expansion is a special token, which points to the builtin's internal -definition. This token meaningful primarily as the second argument to +definition. This token is only meaningful as the second argument to @code{define} (and @code{pushdef}), and is silently converted to an -empty string in many other contexts. +empty string in most other contexts. Combining a builtin with anything +else is not supported; a warning is issued and the builtin is omitted +from the final expansion. The macro @code{defn} is recognized only with parameters. @end deffn @@ -2381,122 +2320,45 @@ defn([l], [r]) @cindex builtins, special tokens @cindex tokens, builtin macro -Using @code{defn} to generate special tokens for builtin macros will -generate a warning in contexts where a macro name is expected. But in -contexts that operate on text, the builtin token is just silently -converted to an empty string. As of M4 1.6, expansion of user macros -will also preserve builtin tokens. However, any use of builtin tokens -outside of the second argument to @code{define} and @code{pushdef} is -generally not portable, since earlier @acronym{GNU} M4 versions, as well -as other @code{m4} implementations, vary on how such tokens are treated. +Using @code{defn} to generate special tokens for builtin macros outside +of expected contexts can sometimes trigger warnings. But most of the +time, such tokens are silently converted to the empty string. @example $ @kbd{m4 -d} defn(`defn') @result{} define(defn(`divnum'), `cannot redefine a builtin token') -@error{}m4:stdin:2: warning: define: invalid macro name ignored +@error{}m4:stdin:2: Warning: define: invalid macro name ignored @result{} divnum @result{}0 len(defn(`divnum')) @result{}0 -define(`echo', `$@@') -@result{} -define(`mydivnum', shift(echo(`', defn(`divnum')))) -@result{} -mydivnum -@result{}0 -define(`', `empty-$1') -@result{} -defn(defn(`divnum')) -@error{}m4:stdin:9: warning: defn: invalid macro name ignored -@result{} -pushdef(defn(`divnum'), `oops') -@error{}m4:stdin:10: warning: pushdef: invalid macro name ignored -@result{} -traceon(defn(`divnum')) -@error{}m4:stdin:11: warning: traceon: invalid macro name ignored -@result{} -indir(defn(`divnum'), `string') -@error{}m4:stdin:12: warning: indir: invalid macro name ignored -@result{} -indir(`', `string') -@result{}empty-string -traceoff(defn(`divnum')) -@error{}m4:stdin:14: warning: traceoff: invalid macro name ignored -@result{} -popdef(defn(`divnum')) -@error{}m4:stdin:15: warning: popdef: invalid macro name ignored -@result{} -dumpdef(defn(`divnum')) -@error{}m4:stdin:16: warning: dumpdef: invalid macro name ignored -@result{} -undefine(defn(`divnum')) -@error{}m4:stdin:17: warning: undefine: invalid macro name ignored -@result{} -dumpdef(`') -@error{}:@tabchar{}`empty-$1' -@result{} -m4symbols(defn(`divnum')) -@error{}m4:stdin:19: warning: m4symbols: invalid macro name ignored -@result{} -define(`foo', `define(`$1', $2)')dnl -foo(`bar', defn(`divnum')) -@result{} -bar -@result{}0 @end example -As of M4 1.6, @code{defn} can warn if @var{name} is not a macro, by -using @code{debugmode} (@pxref{Debugmode}) or the command line option -@option{-d} (@option{--debugmode}, @pxref{Debugging options, , Invoking -m4}). Also, @code{defn} with multiple arguments can join text with -builtin tokens. However, when defining a macro via @code{define} or -@code{pushdef}, a warning is issued and the builtin token ignored if the -builtin token does not occur in isolation. A future version of -@acronym{GNU} M4 may lift this restriction. +Also note that @code{defn} with multiple arguments can only join text +macros, not builtins, although a future version of GNU M4 may +lift this restriction. @example $ @kbd{m4 -d} -defn(`foo') -@error{}m4:stdin:1: warning: defn: undefined macro `foo' -@result{} -debugmode(`-d') -@result{} -defn(`foo') -@result{} define(`a', `A')define(`AA', `b') @result{} traceon(`defn', `define') @result{} defn(`a', `divnum', `a') -@error{}m4trace: -1- defn(`a', `divnum', `a') -> ``A'<divnum>`A'' +@error{}m4:stdin:3: Warning: cannot concatenate builtin `divnum' +@error{}m4trace: -1- defn(`a', `divnum', `a') -> ``A'`A'' @result{}AA define(`mydivnum', defn(`divnum', `divnum'))mydivnum -@error{}m4trace: -2- defn(`divnum', `divnum') -> `<divnum><divnum>' -@error{}m4:stdin:7: warning: define: cannot concatenate builtins -@error{}m4trace: -1- define(`mydivnum', `<divnum><divnum>') -> `' -@result{} -traceoff(`defn', `define')dumpdef(`mydivnum') -@error{}mydivnum:@tabchar{}`' -@result{} -define(`mydivnum', defn(`divnum')defn(`divnum'))mydivnum -@error{}m4:stdin:9: warning: define: cannot concatenate builtins -@result{} -define(`mydivnum', defn(`divnum')`a')mydivnum -@error{}m4:stdin:10: warning: define: cannot concatenate builtins -@result{}A -define(`mydivnum', `a'defn(`divnum'))mydivnum -@error{}m4:stdin:11: warning: define: cannot concatenate builtins -@result{}A -define(`q', ``$@@'') -@result{} -define(`foo', q(`a', defn(`divnum')))foo -@error{}m4:stdin:13: warning: define: cannot concatenate builtins -@result{}a, -ifdef(`foo', `yes', `no') -@result{}yes +@error{}m4:stdin:4: Warning: cannot concatenate builtin `divnum' +@error{}m4:stdin:4: Warning: cannot concatenate builtin `divnum' +@error{}m4trace: -2- defn(`divnum', `divnum') +@error{}m4trace: -1- define(`mydivnum', `') +@result{} +traceoff(`defn', `define') +@result{} @end example @node Pushdef @@ -2512,8 +2374,8 @@ It is possible to redefine a macro temporarily, reverting to the previous definition at a later time. This is done with the builtins @code{pushdef} and @code{popdef}: -@deffn {Builtin (m4)} pushdef (@var{name}, @ovar{expansion}) -@deffnx {Builtin (m4)} popdef (@var{name}@dots{}) +@deffn Builtin pushdef (@var{name}, @ovar{expansion}) +@deffnx Builtin popdef (@var{name}@dots{}) Analogous to @code{define} and @code{undefine}. These macros work in a stack-like fashion. A macro is temporarily @@ -2524,9 +2386,7 @@ exactly like @code{define}. If a macro has several definitions (of which only one is accessible), the topmost definition can be removed with @code{popdef}. If there is -no previous definition, @code{popdef} behaves like @code{undefine}, and -if there is no definition at all, the @samp{d} debug level controls -whether a warning is issued (@pxref{Debugmode}). +no previous definition, @code{popdef} behaves like @code{undefine}. The expansion of both @code{pushdef} and @code{popdef} is void. The macros @code{pushdef} and @code{popdef} are recognized only with @@ -2563,11 +2423,11 @@ foo If a macro with several definitions is redefined with @code{define}, the topmost definition is @emph{replaced} with the new definition. If it is removed with @code{undefine}, @emph{all} the definitions are removed, -and not only the topmost one. However, @acronym{POSIX} allows other +and not only the topmost one. However, POSIX allows other implementations that treat @code{define} as replacing an entire stack of definitions with a single new definition, so to be portable to other implementations, it may be worth explicitly using @code{popdef} and -@code{pushdef} rather than relying on the @acronym{GNU} behavior of +@code{pushdef} rather than relying on the GNU behavior of @code{define}. @example @@ -2599,156 +2459,19 @@ revealing the former definition. It is possible to temporarily redefine a builtin with @code{pushdef} and @code{defn}. -As of M4 1.6, @code{popdef} can warn if @var{name} is not a macro, by -using @code{debugmode} (@pxref{Debugmode}) or the command line option -@option{-d} (@option{--debugmode}, @pxref{Debugging options, , Invoking -m4}). - -@example -define(`a', `1') -@result{} -popdef -@result{}popdef -popdef(`a', `a') -@error{}m4:stdin:3: warning: popdef: undefined macro `a' -@result{} -debugmode(`-d') -@result{} -popdef(`a') -@result{} -@end example - -@node Renamesyms -@section Renaming macros with regular expressions - -@cindex regular expressions -@cindex macros, how to rename -@cindex renaming macros -@cindex @acronym{GNU} extensions -Sometimes it is desirable to rename multiple symbols without having to -use a long sequence of calls to @code{define}. The @code{renamesyms} -builtin allows this: - -@deffn {Builtin (gnu)} renamesyms (@var{regexp}, @var{replacement}, @ - @ovar{resyntax}) -Global renaming of macros is done by @code{renamesyms}, which selects -all macros with names that match @var{regexp}, and renames each match -according to @var{replacement}. It is unspecified what happens if the -rename causes multiple macros to map to the same name. -@comment FIXME - right now, collisions cause a core dump on some platforms: -@comment define(bar,1)define(baz,2)renamesyms(^ba., baa)dumpdef(`baa') - -If @var{resyntax} is given, the particular flavor of regular -expression understood with respect to @var{regexp} can be changed from -the current default. @xref{Changeresyntax}, for details of the values -that can be given for this argument. - -A macro that does not have a name that matches @var{regexp} is left -with its original name. If only part of the name matches, any part of -the name that is not covered by @var{regexp} is copied to the -replacement name. Whenever a match is found in the name, the search -proceeds from the end of the match, so no character in the original -name can be substituted twice. If @var{regexp} matches a string of -zero length, the start position for the continued search is -incremented to avoid infinite loops. - -Where a replacement is to be made, @var{replacement} replaces the -matched text in the original name, with @samp{\@var{n}} substituted by -the text matched by the @var{n}th parenthesized sub-expression of -@var{regexp}, and @samp{\&} being the text matched by the entire -regular expression. - -The expansion of @code{renamesyms} is void. -The macro @code{renamesyms} is recognized only with parameters. -This macro was added in M4 2.0. -@end deffn - -The following example starts with a rename similar to the -@option{--prefix-builtins} option (or @option{-P}), prefixing every -macro with @code{m4_}. However, note that @option{-P} only renames M4 -builtin macros, even if other macros were defined previously, while -@code{renamesyms} will rename any macros that match when it runs, -including text macros. The rest of the example demonstrates the -behavior of unanchored regular expressions in symbol renaming. - -@comment options: -Dfoo=bar -P -@example -$ @kbd{m4 -Dfoo=bar -P} -foo -@result{}bar -m4_foo -@result{}m4_foo -m4_defn(`foo') -@result{}bar -@end example - -@example -$ @kbd{m4} -define(`foo', `bar') -@result{} -renamesyms(`^.*$', `m4_\&') -@result{} -foo -@result{}foo -m4_foo -@result{}bar -m4_defn(`m4_foo') -@result{}bar -m4_renamesyms(`f', `g') -@result{} -m4_igdeg(`m4_goo', `m4_goo') -@result{}bar -@end example - -If @var{resyntax} is given, @var{regexp} must be given according to -the syntax chosen, though the default regular expression syntax -remains unchanged for other invocations. Here is a more realistic -example that performs a similar renaming on macros, except that it -ignores macros with names that begin with @samp{_}, and avoids creating -macros with names that begin with @samp{m4_m4}. - -@example -renamesyms(`^[^_]\w*$', `m4_\&') -@result{} -m4_renamesyms(`^m4_m4(\w*)$', `m4_\1', `POSIX_EXTENDED') -@result{} -m4_wrap(__line__ -) -@result{} -^D -@result{}3 -@end example - -When a symbol has multiple definitions, thanks to @code{pushdef}, the -entire stack is renamed. - -@example -pushdef(`foo', `1')pushdef(`foo', `2') -@result{} -renamesyms(`^foo$', `bar') -@result{} -bar -@result{}2 -popdef(`bar')bar -@result{}1 -popdef(`bar')bar -@result{}bar -@end example - @node Indir @section Indirect call of macros @cindex indirect call of macros @cindex call of macros, indirect @cindex macros, indirect call of -@cindex @acronym{GNU} extensions +@cindex GNU extensions Any macro can be called indirectly with @code{indir}: -@deffn {Builtin (gnu)} indir (@var{name}, @ovar{args@dots{}}) -Results in a call to the macro @var{name}, which is passed the rest of -the arguments @var{args}. If @var{name} is not defined, the expansion -is void, and the @samp{d} debug level controls whether a warning is -issued (@pxref{Debugmode}). +@deffn Builtin indir (@var{name}, @ovar{args@dots{}}) +Results in a call to the macro @var{name}, which is passed the +rest of the arguments @var{args}. If @var{name} is not defined, an +error message is printed, and the expansion is void. The macro @code{indir} is recognized only with parameters. @end deffn @@ -2785,11 +2508,7 @@ f(define(`f', `2')) indir(`f', define(`f', `3')) @result{}3 indir(`f', undefine(`f')) -@error{}m4:stdin:4: warning: indir: undefined macro `f' -@result{} -debugmode(`-d') -@result{} -indir(`f') +@error{}m4:stdin:4: undefined macro `f' @result{} @end example @@ -2801,32 +2520,18 @@ string. @example $ @kbd{m4 -d} indir(defn(`defn'), `divnum') -@error{}m4:stdin:1: warning: indir: invalid macro name ignored +@error{}m4:stdin:1: Warning: indir: invalid macro name ignored @result{} indir(`define', defn(`defn'), `divnum') -@error{}m4:stdin:2: warning: define: invalid macro name ignored +@error{}m4:stdin:2: Warning: define: invalid macro name ignored @result{} indir(`define', `foo', defn(`divnum')) @result{} foo @result{}0 indir(`divert', defn(`foo')) -@error{}m4:stdin:5: warning: divert: empty string treated as 0 -@result{} -@end example - -Warning messages issued on behalf of an indirect macro use an -unambiguous representation of the macro name, using escape sequences -similar to C strings, and with colons also quoted. - -@example -define(`%%:\ -odd', defn(`divnum')) +@error{}m4:stdin:5: empty string treated as 0 in builtin `divert' @result{} -indir(`%%:\ -odd', `extra') -@error{}m4:stdin:3: warning: %%\:\\\nodd: extra arguments ignored: 1 > 0 -@result{}0 @end example @node Builtin @@ -2835,21 +2540,13 @@ odd', `extra') @cindex indirect call of builtins @cindex call of builtins, indirect @cindex builtins, indirect call of -@cindex @acronym{GNU} extensions +@cindex GNU extensions Builtin macros can be called indirectly with @code{builtin}: -@deffn {Builtin (gnu)} builtin (@var{name}, @ovar{args@dots{}}) -@deffnx {Builtin (gnu)} builtin (@code{defn(`builtin')}, @var{name1}) +@deffn Builtin builtin (@var{name}, @ovar{args@dots{}}) Results in a call to the builtin @var{name}, which is passed the rest of the arguments @var{args}. If @var{name} does not name a -builtin, the expansion is void, and the @samp{d} debug level controls -whether a warning is issued (@pxref{Debugmode}). - -As a special case, if @var{name} is exactly the special token -representing the @code{builtin} macro, as obtained by @code{defn} -(@pxref{Defn}), then @var{args} must consist of a single @var{name1}, -and the expansion is the special token representing the builtin macro -named by @var{name1}. +builtin, an error message is printed, and the expansion is void. The macro @code{builtin} is recognized only with parameters. @end deffn @@ -2896,138 +2593,68 @@ $ @kbd{m4 -P} m4_builtin(`divnum') @result{}0 m4_builtin(`m4_divnum') -@error{}m4:stdin:2: warning: m4_builtin: undefined builtin `m4_divnum' +@error{}m4:stdin:2: undefined builtin `m4_divnum' @result{} m4_indir(`divnum') -@error{}m4:stdin:3: warning: m4_indir: undefined macro `divnum' +@error{}m4:stdin:3: undefined macro `divnum' @result{} m4_indir(`m4_divnum') @result{}0 -m4_debugmode(`-d') -@result{} -m4_builtin(`m4_divnum') -@result{} @end example Note that @code{indir} and @code{builtin} can be used to invoke builtins without arguments, even when they normally require parameters to be -recognized; but it will provoke a warning, and the expansion will behave -as though empty strings had been passed as the required arguments. +recognized; but it will provoke a warning, and result in a void expansion. @example builtin @result{}builtin builtin() -@error{}m4:stdin:2: warning: builtin: undefined builtin `' +@error{}m4:stdin:2: undefined builtin `' @result{} builtin(`builtin') -@error{}m4:stdin:3: warning: builtin: too few arguments: 0 < 1 +@error{}m4:stdin:3: Warning: too few arguments to builtin `builtin' @result{} builtin(`builtin',) -@error{}m4:stdin:4: warning: builtin: undefined builtin `' +@error{}m4:stdin:4: undefined builtin `' @result{} builtin(`builtin', ``' ') -@error{}m4:stdin:5: warning: builtin: undefined builtin ``\'\n' +@error{}m4:stdin:5: undefined builtin ``' +@error{}' @result{} indir(`index') -@error{}m4:stdin:7: warning: index: too few arguments: 0 < 2 -@result{}0 +@error{}m4:stdin:7: Warning: too few arguments to builtin `index' +@result{} @end example -Normally, once a builtin macro is undefined, the only way to retrieve -its functionality is by defining a new macro that expands to -@code{builtin} under the hood. But this extra layer of expansion is -slightly inefficient, not to mention the fact that it is not robust to -changes in the current quoting scheme due to @code{changequote} -(@pxref{Changequote}). On the other hand, defining a macro to the -special token produced by @code{defn} (@pxref{Defn}) is very efficient, -and avoids the need for quoting within the macro definition; but -@code{defn} only works if the desired macro is already defined by some -other name. So @code{builtin} provides a special case where it is -possible to retrieve the same special token representing a builtin as -what @code{defn} would provide, were the desired macro still defined. -This feature is activated by passing @code{defn(`builtin')} as the first -argument to builtin. Normally, passing a special token representing a -macro as @var{name} results in a warning and an empty expansion, but in -this case, if the second argument @var{name1} names a valid builtin, -there is no warning and the expansion is the appropriate special -token. In fact, with just the @code{builtin} macro accessible, it is -possible to reconstitute the entire startup state of @code{m4}. - -In the example below, compare the number of macro invocations performed -by @code{defn1} and @code{defn2}, and the differences once quoting is -changed. +@ignore +@comment This example is not worth putting in the manual, but it is +@comment needed for full coverage. Autoconf's m4_include relies heavily +@comment on this feature. @example -$ @kbd{m4 -d} -undefine(`defn') -@result{} -define(`foo', `bar') -@result{} -define(`defn1', `builtin(`defn', $@@)') -@result{} -define(`defn2', builtin(builtin(`defn', `builtin'), `defn')) -@result{} -dumpdef(`defn1', `defn2') -@error{}defn1:@tabchar{}`builtin(`defn', $@@)' -@error{}defn2:@tabchar{}<defn> -@result{} -traceon -@result{} -defn1(`foo') -@error{}m4trace: -1- defn1(`foo') -> `builtin(`defn', `foo')' -@error{}m4trace: -1- builtin(`defn', `foo') -> ``bar'' +builtin(`include', `foo')dnl @result{}bar -defn2(`foo') -@error{}m4trace: -1- defn2(`foo') -> ``bar'' -@result{}bar -traceoff -@error{}m4trace: -1- traceoff -> `' -@result{} -changequote(`[', `]') -@result{} -defn1([foo]) -@error{}m4:stdin:11: warning: builtin: undefined builtin ``defn\'' -@result{} -defn2([foo]) -@result{}bar -define([defn1], [builtin([defn], $@@)]) -@result{} -defn1([foo]) -@result{}bar -changequote -@result{} -defn1(`foo') -@error{}m4:stdin:16: warning: builtin: undefined builtin `[defn]' -@result{} @end example -@node M4symbols -@section Getting the defined macro names - -@cindex macro names, listing -@cindex listing macro names -@cindex currently defined macros -@cindex @acronym{GNU} extensions -The name of the currently defined macros can be accessed by -@code{m4symbols}: - -@deffn {Builtin (gnu)} m4symbols (@ovar{names@dots{}}) -Without arguments, @code{m4symbols} expands to a sorted list of quoted -strings, separated by commas. This contrasts with @code{dumpdef} -(@pxref{Dumpdef}), whose output cannot be accessed by @code{m4} -programs. - -When given arguments, @code{m4symbols} returns the sorted subset of the -@var{names} currently defined, and silently ignores the rest. -This macro was added in M4 2.0. -@end deffn +@comment And this example triggers a regression present in 1.4.10b. @example -m4symbols(`ifndef', `ifdef', `define', `undef') -@result{}define,ifdef +define(`s', `builtin(`shift', $@@)')dnl +define(`loop', `ifelse(`$2', `', `-', `$1$2: $0(`$1', s(s($@@)))')')dnl +loop(`1') +@result{}- +loop(`1', `2') +@result{}12: - +loop(`1', `2', `3') +@result{}12: 13: - +loop(`1', `2', `3', `4') +@result{}12: 13: 14: - +loop(`1', `2', `3', `4', `5') +@result{}12: 13: 14: 15: - @end example +@end ignore @node Conditionals @chapter Conditionals, loops, and recursion @@ -3055,7 +2682,7 @@ something a number of times, or while some condition is true. There are two different builtin conditionals in @code{m4}. The first is @code{ifdef}: -@deffn {Builtin (m4)} ifdef (@var{name}, @var{string-1}, @ovar{string-2}) +@deffn Builtin ifdef (@var{name}, @var{string-1}, @ovar{string-2}) If @var{name} is defined as a macro, @code{ifdef} expands to @var{string-1}, otherwise to @var{string-2}. If @var{string-2} is omitted, it is taken to be the empty string (according to the normal @@ -3072,24 +2699,8 @@ define(`foo', `') ifdef(`foo', ``foo' is defined', ``foo' is not defined') @result{}foo is defined ifdef(`no_such_macro', `yes', `no', `extra argument') -@error{}m4:stdin:4: warning: ifdef: extra arguments ignored: 4 > 3 -@result{}no -@end example - -As of M4 1.6, @code{ifdef} transparently handles builtin tokens -generated by @code{defn} (@pxref{Defn}) that occur in either -@var{string}, although a warning is issued for invalid macro names. - -@example -define(`', `empty') -@result{} -ifdef(defn(`defn'), `yes', `no') -@error{}m4:stdin:2: warning: ifdef: invalid macro name ignored +@error{}m4:stdin:4: Warning: excess arguments to builtin `ifdef' ignored @result{}no -define(`foo', ifdef(`divnum', defn(`divnum'), `undefined')) -@result{} -foo -@result{}0 @end example @node Ifelse @@ -3102,10 +2713,10 @@ The other conditional, @code{ifelse}, is much more powerful. It can be used as a way to introduce a long comment, as an if-else construct, or as a multibranch, depending on the number of arguments supplied: -@deffn {Builtin (m4)} ifelse (@var{comment}) -@deffnx {Builtin (m4)} ifelse (@var{string-1}, @var{string-2}, @var{equal}, @ +@deffn Builtin ifelse (@var{comment}) +@deffnx Builtin ifelse (@var{string-1}, @var{string-2}, @var{equal}, @ @ovar{not-equal}) -@deffnx {Builtin (m4)} ifelse (@var{string-1}, @var{string-2}, @var{equal-1}, @ +@deffnx Builtin ifelse (@var{string-1}, @var{string-2}, @var{equal-1}, @ @var{string-3}, @var{string-4}, @var{equal-2}, @dots{}, @ovar{not-equal}) Used with only one argument, the @code{ifelse} simply discards it and produces no output. @@ -3125,14 +2736,14 @@ The macro @code{ifelse} is recognized only with parameters. Using only one argument is a common @code{m4} idiom for introducing a block comment, as an alternative to repeatedly using @code{dnl}. This -special usage is recognized by @acronym{GNU} @code{m4}, so that in this +special usage is recognized by GNU @code{m4}, so that in this case, the warning about missing arguments is never triggered. @example ifelse(`some comments') @result{} ifelse(`foo', `bar') -@error{}m4:stdin:2: warning: ifelse: too few arguments: 2 < 3 +@error{}m4:stdin:2: Warning: too few arguments to builtin `ifelse' @result{} @end example @@ -3184,34 +2795,75 @@ calls for an example: @example ifelse(`foo', `bar', `third', `gnu', `gnats') -@error{}m4:stdin:1: warning: ifelse: extra arguments ignored: 5 > 4 +@error{}m4:stdin:1: Warning: excess arguments to builtin `ifelse' ignored @result{}gnu ifelse(`foo', `bar', `third', `gnu', `gnats', `sixth') @result{} ifelse(`foo', `bar', `third', `gnu', `gnats', `sixth', `seventh') @result{}seventh ifelse(`foo', `bar', `3', `gnu', `gnats', `6', `7', `8') -@error{}m4:stdin:4: warning: ifelse: extra arguments ignored: 8 > 7 +@error{}m4:stdin:4: Warning: excess arguments to builtin `ifelse' ignored @result{}7 @end example -As of M4 1.6, @code{ifelse} transparently handles builtin tokens -generated by @code{defn} (@pxref{Defn}). Because of this, it is always -safe to compare two macro definitions, without worrying whether the -macro might be a builtin. +@ignore +@comment Stress tests, not worth documenting. +@comment Ensure that references compared to strings work regardless of +@comment similar prefixes. @example -ifelse(defn(`defn'), `', `yes', `no') +define(`e', `$@@')define(`long', `01234567890123456789') +@result{} +ifelse(long, `01234567890123456789', `yes', `no') +@result{}yes +ifelse(`01234567890123456789', long, `yes', `no') +@result{}yes +ifelse(long, `01234567890123456789-', `yes', `no') @result{}no -ifelse(defn(`defn'), defn(`divnum'), `yes', `no') +ifelse(`01234567890123456789-', long, `yes', `no') @result{}no -ifelse(defn(`defn'), defn(`defn'), `yes', `no') +ifelse(e(long), `01234567890123456789', `yes', `no') @result{}yes -define(`foo', ifelse(`', `', defn(`divnum'))) -@result{} -foo -@result{}0 +ifelse(`01234567890123456789', e(long), `yes', `no') +@result{}yes +ifelse(e(long), `01234567890123456789-', `yes', `no') +@result{}no +ifelse(`01234567890123456789-', e(long), `yes', `no') +@result{}no +ifelse(-e(long), `-01234567890123456789', `yes', `no') +@result{}yes +ifelse(-`01234567890123456789', -e(long), `yes', `no') +@result{}yes +ifelse(-e(long), `-01234567890123456789-', `yes', `no') +@result{}no +ifelse(`-01234567890123456789-', -e(long), `yes', `no') +@result{}no +ifelse(-e(long)-, `-01234567890123456789-', `yes', `no') +@result{}yes +ifelse(-`01234567890123456789-', -e(long)-, `yes', `no') +@result{}yes +ifelse(-e(long)-, `-01234567890123456789', `yes', `no') +@result{}no +ifelse(`-01234567890123456789', -e(long)-, `yes', `no') +@result{}no +ifelse(`-'e(long), `-01234567890123456789', `yes', `no') +@result{}yes +ifelse(-`01234567890123456789', `-'e(long), `yes', `no') +@result{}yes +ifelse(`-'e(long), `-01234567890123456789-', `yes', `no') +@result{}no +ifelse(`-01234567890123456789-', `-'e(long), `yes', `no') +@result{}no +ifelse(`-'e(long)`-', `-01234567890123456789-', `yes', `no') +@result{}yes +ifelse(-`01234567890123456789-', `-'e(long)`-', `yes', `no') +@result{}yes +ifelse(`-'e(long)`-', `-01234567890123456789', `yes', `no') +@result{}no +ifelse(`-01234567890123456789', `-'e(long)`-', `yes', `no') +@result{}no @end example +@end ignore Naturally, the normal case will be slightly more advanced than these examples. A common use of @code{ifelse} is in macros implementing loops @@ -3233,7 +2885,7 @@ previously. There is a builtin macro, @code{shift}, which can, among other things, be used for iterating through the actual arguments to a macro: -@deffn {Builtin (m4)} shift (@var{arg1}, @dots{}) +@deffn Builtin shift (@var{arg1}, @dots{}) Takes any number of arguments, and expands to all its arguments except @var{arg1}, separated by commas, with each argument quoted. @@ -3511,7 +3163,7 @@ than @samp{joinall(`,', @var{args})} for producing the same output. @cindex arguments, more than nine One more useful macro based on @code{shift} allows portably selecting an arbitrary argument (usually greater than the ninth argument), without -relying on the @acronym{GNU} extension of multi-digit arguments +relying on the GNU extension of multi-digit arguments (@pxref{Arguments}). @deffn Composite argn (@var{n}, @dots{}) @@ -3998,20 +3650,8 @@ undivert(`curry.m4')dnl Unfortunately, with M4 1.4.x, @code{curry} is unable to handle builtin tokens, which are silently flattened to the empty string when passed -through another text macro. The following example demonstrates a usage -of @code{curry} that works in M4 1.6, but is not portable to earlier -versions: - -@comment examples -@example -$ @kbd{m4 -I examples} -include(`curry.m4') -@result{} -curry(`define', `mylen')(defn(`len')) -@result{} -mylen(`abc') -@result{}3 -@end example +through another text macro. This limitation will be lifted in a future +release of M4. @cindex renaming macros @cindex copying macros @@ -4029,9 +3669,10 @@ via this macro. @end deffn The implementation is relatively straightforward (although since it uses -@code{curry}, it is unable to copy builtin macros when used with M4 -1.4.x. See if you can design a portable version that works across all -M4 versions, or @pxref{Improved copy, , Answers}). +@code{curry}, it is unable to copy builtin macros, such as the second +definition of @code{a} as a synonym for @code{divnum}. See if you can +design a version that works around this limitation, or @pxref{Improved +copy, , Answers}). @comment examples @example @@ -4050,8 +3691,8 @@ rename(`b', `c') @result{} a b c @result{}2 b 2 -popdef(`a', `c')a c -@result{}0 0 +popdef(`a', `c')c a +@result{} 0 popdef(`a', `c')a c @result{}1 1 @end example @@ -4068,9 +3709,8 @@ Fortunately, there is support for macro debugging in @code{m4}. @menu * Dumpdef:: Displaying macro definitions * Trace:: Tracing macro calls -* Debugmode:: Controlling debugging options -* Debuglen:: Limiting debug output -* Debugfile:: Saving debugging output +* Debug Levels:: Controlling debugging output +* Debug Output:: Saving debugging output @end menu @node Dumpdef @@ -4083,14 +3723,12 @@ Fortunately, there is support for macro debugging in @code{m4}. If you want to see what a name expands into, you can use the builtin @code{dumpdef}: -@deffn {Builtin (m4)} dumpdef (@ovar{name@dots{}}) -Accepts any number of arguments. If called without any arguments, it -displays the definitions of all known names, otherwise it displays the -definitions of each @var{name} given, sorted by name. If a @var{name} -is undefined, the @samp{d} debug level controls whether a warning is -issued (@pxref{Debugmode}). Likewise, the @samp{o} debug level controls -whether the output is issued to standard error or the current debug -file (@pxref{Debugfile}). +@deffn Builtin dumpdef (@ovar{names@dots{}}) +Accepts any number of arguments. If called without any arguments, +it displays the definitions of all known names, otherwise it displays +the definitions of the @var{names} given. The output is printed to the +current debug file (usually standard error), and is sorted by name. If +an unknown name is encountered, a warning is printed. The expansion of @code{dumpdef} is void. @end deffn @@ -4120,44 +3758,12 @@ f(popdef(`f')dumpdef(`f')) @error{}f:@tabchar{}``$0'1' @result{}f2 f(popdef(`f')dumpdef(`f')) -@error{}m4:stdin:3: warning: dumpdef: undefined macro `f' +@error{}m4:stdin:3: undefined macro `f' @result{}f1 -debugmode(`-d') -@result{} -dumpdef(`f') -@result{} @end example -@xref{Debugmode}, for information on how the @samp{m}, @samp{q}, and -@samp{s} flags affect the details of the display. Remember, the -@samp{q} flag is implied when the @option{--debug} option (@option{-d}, -@pxref{Debugging options, , Invoking m4}) is used in the command line -without arguments. Also, @option{--debuglen} (@pxref{Debuglen}) can affect -output, by truncating longer strings (but not builtin and module names). - -@comment options: -ds -l3 -@example -$ @kbd{m4 -ds -l 3} -pushdef(`foo', `1 long string') -@result{} -pushdef(`foo', defn(`divnum')) -@result{} -pushdef(`foo', `3') -@result{} -debugmode(`+m') -@result{} -dumpdef(`foo', `dnl', `indir', `__gnu__') -@error{}__gnu__:@tabchar{}@{gnu@} -@error{}dnl:@tabchar{}<dnl>@{m4@} -@error{}foo:@tabchar{}3, <divnum>@{m4@}, 1 l... -@error{}indir:@tabchar{}<indir>@{gnu@} -@result{} -debugmode(`-ms')debugmode(`+q') -@result{} -dumpdef(`foo') -@error{}foo:@tabchar{}`3' -@result{} -@end example +@xref{Debug Levels}, for information on controlling the details of the +display. @node Trace @section Tracing macro calls @@ -4169,17 +3775,14 @@ dumpdef(`foo') It is possible to trace macro calls and expansions through the builtins @code{traceon} and @code{traceoff}: -@deffn {Builtin (m4)} traceon (@ovar{names@dots{}}) -@deffnx {Builtin (m4)} traceoff (@ovar{names@dots{}}) +@deffn Builtin traceon (@ovar{names@dots{}}) +@deffnx Builtin traceoff (@ovar{names@dots{}}) When called without any arguments, @code{traceon} and @code{traceoff} -will turn tracing on and off, respectively, for all macros, identical to -using the @samp{t} flag of @code{debugmode} (@pxref{Debugmode}). +will turn tracing on and off, respectively, for all currently defined +macros. When called with arguments, only the macros listed in @var{names} are -affected, whether or not they are currently defined. A macro's -expansion will be traced if global tracing is on, or if the individual -macro tracing flag is set; to avoid tracing a macro, both the global -flag and the macro must have tracing off. +affected, whether or not they are currently defined. The expansion of @code{traceon} and @code{traceoff} is void. @end deffn @@ -4187,8 +3790,8 @@ The expansion of @code{traceon} and @code{traceoff} is void. Whenever a traced macro is called and the arguments have been collected, the call is displayed. If the expansion of the macro call is not void, the expansion can be displayed after the call. The output is printed -to the current debug file (defaulting to standard error, -@pxref{Debugfile}). +to the current debug file (defaulting to standard error, @pxref{Debug +Output}). @example $ @kbd{m4 -d} @@ -4215,7 +3818,8 @@ option @option{--nesting-limit} (or @option{-L}, @pxref{Limits control, @option{-t}) can be used to invoke @code{traceon(@var{name})} before parsing input. -@comment options: -d-V -L3 -tifelse +@comment The explicit -dp neutralizes the testsuite default of -d. +@comment options: -dp -L3 -tifelse @comment status: 1 @example $ @kbd{m4 -L 3 -t ifelse} @@ -4244,17 +3848,6 @@ traceon(`foo') foo @result{}foo defn(`foo') -@error{}m4:stdin:4: warning: defn: undefined macro `foo' -@result{} -undefine(`foo') -@error{}m4:stdin:5: warning: undefine: undefined macro `foo' -@result{} -pushdef(`foo') -@result{} -popdef(`foo') -@result{} -popdef(`foo') -@error{}m4:stdin:8: warning: popdef: undefined macro `foo' @result{} define(`foo', `bar') @result{} @@ -4266,13 +3859,17 @@ undefine(`foo') ifdef(`foo', `yes', `no') @result{}no indir(`foo') -@error{}m4:stdin:13: warning: indir: undefined macro `foo' +@error{}m4:stdin:9: undefined macro `foo' @result{} define(`foo', `blah') @result{} foo @error{}m4trace: -1- foo -> `blah' @result{}blah +traceoff +@result{} +foo +@result{}blah @end example Tracing even works on builtins. However, @code{defn} (@pxref{Defn}) @@ -4283,10 +3880,10 @@ $ @kbd{m4 -d} traceon(`traceon') @result{} traceon(`traceoff') -@error{}m4trace: -1- traceon(`traceoff') -> `' +@error{}m4trace: -1- traceon(`traceoff') @result{} traceoff(`traceoff') -@error{}m4trace: -1- traceoff(`traceoff') -> `' +@error{}m4trace: -1- traceoff(`traceoff') @result{} traceoff(`traceon') @result{} @@ -4304,151 +3901,34 @@ m4_eval(m4_divnum) @result{}0 @end example -As of @acronym{GNU} M4 2.0, named macro tracing is independent of global -tracing status; calling @code{traceoff} without arguments turns off the -global trace flag, but does not turn off tracing for macros where -tracing was requested by name. Likewise, calling @code{traceon} without -arguments will affect tracing of macros that are not defined yet. This -behavior matches traditional implementations of @code{m4}. - -@example -$ @kbd{m4 -d} -traceon -@result{} -define(`foo', `bar') -@error{}m4trace: -1- define(`foo', `bar') -> `' -@result{} -foo # traced, even though foo was not defined at traceon -@error{}m4trace: -1- foo -> `bar' -@result{}bar # traced, even though foo was not defined at traceon -traceoff(`foo') -@error{}m4trace: -1- traceoff(`foo') -> `' -@result{} -foo # traced, since global tracing is still on -@error{}m4trace: -1- foo -> `bar' -@result{}bar # traced, since global tracing is still on -traceon(`foo') -@error{}m4trace: -1- traceon(`foo') -> `' -@result{} -traceoff -@error{}m4trace: -1- traceoff -> `' -@result{} -foo # traced, since foo is now traced by name -@error{}m4trace: -1- foo -> `bar' -@result{}bar # traced, since foo is now traced by name -traceoff(`foo') -@result{} -foo # untraced -@result{}bar # untraced -@end example - -However, @acronym{GNU} M4 prior to 2.0 had slightly different -semantics, where @code{traceon} without arguments only affected symbols -that were defined at that moment, and @code{traceoff} without arguments -stopped all tracing, even when tracing was requested by macro name. The -addition of the macro @code{m4symbols} (@pxref{M4symbols}) in 2.0 makes it -possible to write a file that approximates the older semantics -regardless of which version of @acronym{GNU} M4 is in use. - -@comment options: -d-V -@example -$ @kbd{m4} -ifdef(`m4symbols', - `define(`traceon', `ifelse(`$#', `0', `builtin(`traceon', m4symbols)', - `builtin(`traceon', $@@)')')dnl -define(`traceoff', `ifelse(`$#', `0', - `builtin(`traceoff')builtin(`traceoff', m4symbols)', - `builtin(`traceoff', $@@)')')')dnl -define(`a', `1') -@result{} -traceon # called before b is defined, so b is not traced -@result{} # called before b is defined, so b is not traced -define(`b', `2') -@error{}m4trace: -1- define -@result{} -a b -@error{}m4trace: -1- a -@result{}1 2 -traceon(`b') -@error{}m4trace: -1- traceon -@error{}m4trace: -1- ifelse -@error{}m4trace: -1- builtin -@result{} -a b -@error{}m4trace: -1- a -@error{}m4trace: -1- b -@result{}1 2 -traceoff # stops tracing b, even though it was traced by name -@error{}m4trace: -1- traceoff -@error{}m4trace: -1- ifelse -@error{}m4trace: -1- builtin -@error{}m4trace: -2- m4symbols -@error{}m4trace: -1- builtin -@result{} # stops tracing b, even though it was traced by name -a b -@result{}1 2 -@end example - -@xref{Debugmode}, for information on controlling the details of the +@xref{Debug Levels}, for information on controlling the details of the display. The format of the trace output is not specified by -@acronym{POSIX}, and varies between implementations of @code{m4}. - -Starting with M4 1.6, tracing also works via @code{indir} -(@pxref{Indir}). However, since tracing is an attribute tracked by -macro names, and @code{builtin} bypasses macro names (@pxref{Builtin}), -it is not possible for @code{builtin} to trace which subsidiary builtin -it invokes. If you are worried about tracking all invocations of a -given builtin, you should also trace @code{builtin}, or enable global -tracing (the @samp{t} debug level, @pxref{Debugmode}). +POSIX, and varies between implementations of @code{m4}. +@ignore +@comment not worth including in the manual, but this tests a trace code +@comment path that was temporarily broken +@comment options: -de --trace ifelse @example -$ @kbd{m4 -d} -define(`my_defn', defn(`defn'))undefine(`defn') +$ @kbd{m4 -de --trace ifelse} +define(`e', `ifelse(`$1', `$2', `ifelse(`$1', `$2', `e(shift($@@))')')') @result{} -define(`foo', `bar')traceon(`foo', `defn', `my_defn') -@result{} -foo -@error{}m4trace: -1- foo -> `bar' -@result{}bar -indir(`foo') -@error{}m4trace: -1- foo -> `bar' -@result{}bar -my_defn(`foo') -@error{}m4trace: -1- my_defn(`foo') -> ``bar'' -@result{}bar -indir(`my_defn', `foo') -@error{}m4trace: -1- my_defn(`foo') -> ``bar'' -@result{}bar -builtin(`defn', `foo') -@result{}bar -debugmode(`+cxt') +e(`1', `1') +@error{}m4trace: -1- ifelse -> ifelse(`1', `1', `e(shift(`1',`1'))') +@error{}m4trace: -1- ifelse -> e(shift(`1',`1')) +@error{}m4trace: -1- ifelse @result{} -builtin(`defn', builtin(`shift', `', `foo')) -@error{}m4trace: -1- id 12: builtin ... = <builtin> -@error{}m4trace: -2- id 13: builtin ... = <builtin> -@error{}m4trace: -2- id 13: builtin(`shift', `', `foo') -> ``foo'' -@error{}m4trace: -1- id 12: builtin(`defn', `foo') -> ``bar'' -@result{}bar -indir(`my_defn', indir(`shift', `', `foo')) -@error{}m4trace: -1- id 14: indir ... = <indir> -@error{}m4trace: -2- id 15: indir ... = <indir> -@error{}m4trace: -2- id 15: shift ... = <shift> -@error{}m4trace: -2- id 15: shift(`', `foo') -> ``foo'' -@error{}m4trace: -2- id 15: indir(`shift', `', `foo') -> ``foo'' -@error{}m4trace: -1- id 14: my_defn ... = <defn> -@error{}m4trace: -1- id 14: my_defn(`foo') -> ``bar'' -@error{}m4trace: -1- id 14: indir(`my_defn', `foo') -> ``bar'' -@result{}bar @end example +@end ignore -@node Debugmode -@section Controlling debugging options +@node Debug Levels +@section Controlling debugging output @cindex controlling debugging output @cindex debugging output, controlling -The @option{--debug} option to @code{m4} (also spelled -@option{--debugmode} or @option{-d}, @pxref{Debugging options, , -Invoking m4}) controls the amount of details presented in three +The @option{-d} option to @code{m4} (or @option{--debug}, +@pxref{Debugging options, , Invoking m4}) controls the amount of details +presented in three categories of output. Trace output is requested by @code{traceon} (@pxref{Trace}), and each line is prefixed by @samp{m4trace:} in relation to a macro invocation. Debug output tracks useful events not @@ -4462,35 +3942,23 @@ following: @table @code @item a In trace output, show the actual arguments that were collected before -invoking the macro. Arguments are subject to length truncation -specified by @code{debuglen} (@pxref{Debuglen}). +invoking the macro. This applies to all macro calls if the @samp{t} +flag is used, otherwise only the macros covered by calls of +@code{traceon}. Arguments are subject to length truncation specified by +the command line option @option{--arglength} (or @option{-l}). @item c -In trace output, show an additional line for each macro call, when the -macro is seen, but before the arguments are collected, and show the -definition of the macro that will be used for the expansion. By -default, only one line is printed, after all arguments are collected and -the expansion determined. The definition is subject to length -truncation specified by @code{debuglen} (@pxref{Debuglen}). This is -often used with the @samp{x} flag. - -@item d -Output a warning on any attempt to dereference an undefined macro via -@code{builtin}, @code{defn}, @code{dumpdef}, @code{indir}, -@code{popdef}, or @code{undefine}. Note that @code{indef}, -@code{m4symbols}, -@code{traceon}, and @code{traceoff} do not dereference undefined macros. -Like any other warning, the warnings enabled by this flag go to standard -error regardless of the current @code{debugfile} setting, and will -change exit status if the command line option @option{--fatal-warnings} -was specified. This flag is useful in diagnosing spelling mistakes in -macro names. It is enabled by default when neither @option{--debug} nor -@option{--fatal-warnings} are specified on the command line. +In trace output, show several trace lines for each macro call. A line +is shown when the macro is seen, but before the arguments are collected; +a second line when the arguments have been collected and a third line +after the call has completed. @item e -In trace output, show the expansion of each macro call. The expansion -is subject to length truncation specified by @code{debuglen} -(@pxref{Debuglen}). +In trace output, show the expansion of each macro call, if it is not +void. This applies to all macro calls if the @samp{t} flag is used, +otherwise only the macros covered by calls of @code{traceon}. The +expansion is subject to length truncation specified by the command line +option @option{--arglength} (or @option{-l}). @item f In debug and trace output, include the name of the current input file in @@ -4504,17 +3972,6 @@ changed. In debug and trace output, include the current input line number in the output line. -@item m -In debug output, print a message each time a module is manipulated -(@pxref{Modules}). In trace output when the @samp{c} flag is in effect, -and in dumpdef output, follow builtin macros with their module name, -surrounded by braces (@samp{@{@}}). - -@item o -Output @code{dumpdef} data to standard error instead of the current -debug file. This can be useful when post-processing trace output, where -interleaving dumpdef and trace output can cause ambiguities. - @item p In debug output, print a message when a named file is found through the path search mechanism (@pxref{Search Path}), giving the actual file name @@ -4525,90 +3982,78 @@ In trace and dumpdef output, quote actual arguments and macro expansions in the display with the current quotes. This is useful in connection with the @samp{a} and @samp{e} flags above. -@item s -In dumpdef output, show the entire stack of definitions associated with -a symbol via @code{pushdef}. - @item t In trace output, trace all macro calls made in this invocation of -@code{m4}. This is equivalent to using @code{traceon} without -arguments. +@code{m4}, regardless of the settings of @code{traceon}. @item x In trace output, add a unique `macro call id' to each line of the trace -output. This is useful in connection with the @samp{c} flag above, to -match where a macro is first recognized with where it is finally -expanded, in spite of intermediate expansions that occur while -collecting arguments. It can also be used in isolation to determine how -many macros have been expanded. +output. This is useful in connection with the @samp{c} flag above. @item V A shorthand for all of the above flags. @end table -As special cases, if @var{flags} starts with a @samp{+}, the named flags -are enabled without impacting other flags, and if it starts with a -@samp{-}, the named flags are disabled without impacting other flags. -Without either of these starting characters, @var{flags} simply replaces -the previous setting. -@comment FIXME - should we accept usage like debugmode(+fl-q)? Also, -@comment should we add debugmode(?) which expands to the current -@comment enabled flags, and debugmode(e?) which expands to e if e is -@comment currently enabled? - -If no flags are specified with the @option{--debug} option, the default is -@samp{+adeq}. Many examples in this manual show their output using -default flags. - -@cindex @acronym{GNU} extensions +If no flags are specified with the @option{-d} option, the default is +@samp{aeq}. The examples throughout this manual assume the default +flags. + +@cindex GNU extensions There is a builtin macro @code{debugmode}, which allows on-the-fly control of the debugging output format: -@deffn {Builtin (gnu)} debugmode (@ovar{flags}) +@deffn Builtin debugmode (@ovar{flags}) The argument @var{flags} should be a subset of the letters listed above. -If no argument is present, all debugging flags are cleared (as if -@var{flags} were an explicit @samp{-V}). With an empty argument, the -most common flags are enabled (as if @var{flags} were an explicit -@samp{+adeq}). If an unknown flag is encountered, an error is issued. +As special cases, if the argument starts with a @samp{+}, the flags are +added to the current debug flags, and if it starts with a @samp{-}, they +are removed. If no argument is present, all debugging flags are cleared +(as if no @option{-d} was given), and with an empty argument the flags +are reset to the default of @samp{aeq}. The expansion of @code{debugmode} is void. @end deffn -@comment options: -d-V +@comment The explicit -dp neutralizes the testsuite default of -d. +@comment options: -dp @example $ @kbd{m4} -define(`foo', `FOO$1') +define(`foo', `FOO') +@result{} +traceon(`foo') @result{} -traceon(`foo', `divnum') +debugmode() @result{} -debugmode()dnl same as debugmode(`+adeq') foo @error{}m4trace: -1- foo -> `FOO' @result{}FOO -debugmode(`V')debugmode(`-q') -@error{}m4trace:stdin:5: -1- id 7: debugmode ... = <debugmode>@{gnu@} -@error{}m4trace:stdin:5: -1- id 7: debugmode(`-q') -> `' -@result{} -foo( -`BAR') -@error{}m4trace:stdin:6: -1- id 8: foo ... = FOO$1 -@error{}m4trace:stdin:6: -1- id 8: foo(BAR) -> FOOBAR -@result{}FOOBAR -debugmode`'dnl same as debugmode(`-V') -@error{}m4trace:stdin:8: -1- id 9: debugmode ... = <debugmode>@{gnu@} -@error{}m4trace:stdin:8: -1- id 9: debugmode ->@w{ } +debugmode +@result{} foo @error{}m4trace: -1- foo @result{}FOO -debugmode(`+clmx') +debugmode(`+l') @result{} -foo(divnum) -@error{}m4trace:11: -1- id 13: foo ... = FOO$1 -@error{}m4trace:11: -2- id 14: divnum ... = <divnum>@{m4@} -@error{}m4trace:11: -2- id 14: divnum -@error{}m4trace:11: -1- id 13: foo -@result{}FOO0 -debugmode(`-m') +foo +@error{}m4trace:8: -1- foo +@result{}FOO +@end example + +The following example demonstrates the behavior of length truncation, +when specified on the command line. Note that each argument and the +final result are individually truncated. Also, the special tokens for +builtin functions are not truncated. + +@comment options: -l6 +@example +$ @kbd{m4 -d -l 6} +define(`echo', `$@@')debugmode(`+t') +@result{} +echo(`1', `long string') +@error{}m4trace: -1- echo(`1', `long s...') -> ``1',`l...' +@result{}1,long string +indir(`echo', defn(`changequote')) +@error{}m4trace: -2- defn(`change...') +@error{}m4trace: -1- indir(`echo', <changequote>) -> ``'' @result{} @end example @@ -4619,114 +4064,36 @@ to macro tracing. @comment options: -dip @example $ @kbd{m4 -dip -I examples} -@error{}m4debug: input read from `stdin' -define(`foo', `m4wrap(`wrapped text -')dnl') -@result{} -include(`incl.m4')dnl -@error{}m4debug: path search for `incl.m4' found `examples/incl.m4' -@error{}m4debug: input read from `examples/incl.m4' -@result{}Include file start -@result{}Include file end -@error{}m4debug: input reverted to stdin, line 3 +@error{}m4debug: input read from stdin +include(`foo')dnl +@error{}m4debug: path search for `foo' found `examples/foo' +@error{}m4debug: input read from examples/foo +@result{}bar +@error{}m4debug: input reverted to stdin, line 1 ^D @error{}m4debug: input exhausted -@error{}m4debug: input from m4wrap recursion level 1 -@result{}wrapped text -@error{}m4debug: input from m4wrap exhausted -@end example - -@node Debuglen -@section Limiting debug output - -@cindex @acronym{GNU} extensions -@cindex arglength -@cindex debuglen -@cindex limiting trace output length -@cindex trace output, limiting length -@cindex dumpdef output, limiting length -When debugging, sometimes it is desirable to reduce the clutter of -arbitrary-length strings, because the prefix carries enough information -to understand the issues. The builtin macro @code{debuglen}, along with -the command line option counterpart @option{--debuglen} (or @option{-l}, -@pxref{Debugging options, , Invoking m4}), allow on-the-fly control of -debugging string lengths: - -@deffn {Builtin (gnu)} debuglen (@var{len}) -The argument @var{len} is an integer that controls how much of -arbitrary-length strings should be output during trace and dumpdef -output. If specified to a non-zero value, then strings longer than that -length are truncated, and @samp{...} included in the output to show that -truncation took place. A warning is issued if @var{len} cannot be -parsed as an integer. -@comment FIXME - make this understand an optional suffix, similar to how -@comment --debuglen does. Also, we need a section documenting scaling -@comment suffixes. -@comment FIXME - should we allow len to be `?', meaning expand to the -@comment current value? - -The macro @code{debuglen} is recognized only with parameters. -@end deffn - -The following example demonstrates the behavior of length truncation. -Note that each argument and the final result are individually truncated. -Also, the special tokens for builtin functions are not truncated. - -@comment options: -l6 -techo -tdefn -@example -$ @kbd{m4 -d -l 6 -t echo -t defn} -debuglen(`oops') -@error{}m4:stdin:1: warning: debuglen: non-numeric argument `oops' -@result{} -define(`echo', `$@@') -@result{} -echo(`1', `long string') -@error{}m4trace: -1- echo(`1', `long s...') -> ``1',`l...' -@result{}1,long string -indir(`echo', defn(`changequote')) -@error{}m4trace: -2- defn(`change...') -> `<changequote>' -@error{}m4trace: -1- echo(<changequote>) -> ``<changequote>'' -@result{} -debuglen -@result{}debuglen -debuglen(`0') -@result{} -echo(`long string') -@error{}m4trace: -1- echo(`long string') -> ``long string'' -@result{}long string -debuglen(`12') -@result{} -echo(`long string') -@error{}m4trace: -1- echo(`long string') -> ``long string...' -@result{}long string @end example -@node Debugfile +@node Debug Output @section Saving debugging output @cindex saving debugging output @cindex debugging output, saving @cindex output, saving debugging -@cindex @acronym{GNU} extensions +@cindex GNU extensions Debug and tracing output can be redirected to files using either the @option{--debugfile} option to @code{m4} (@pxref{Debugging options, , Invoking m4}), or with the builtin macro @code{debugfile}: -@deffn {Builtin (gnu)} debugfile (@ovar{file}) -Send all further debug and trace output to @var{file}, opened in append +@deffn Builtin debugfile (@ovar{file}) +Sends all further debug and trace output to @var{file}, opened in append mode. If @var{file} is the empty string, debug and trace output are discarded. If @code{debugfile} is called without any arguments, debug -and trace output are sent to standard error. Output from @code{dumpdef} -is sent to this file if the debug level @code{o} is not set -(@pxref{Debugmode}). This does not affect +and trace output are sent to standard error. This does not affect warnings, error messages, or @code{errprint} output, which are always sent to standard error. If @var{file} cannot be opened, the current debug file is unchanged, and an error is issued. -When the @option{--safer} option (@pxref{Operation modes, , Invoking -m4}) is in effect, @var{file} must be empty or omitted, since otherwise -an input file could cause the modification of arbitrary files. - The expansion of @code{debugfile} is void. @end deffn @@ -4735,13 +4102,13 @@ $ @kbd{m4 -d} traceon(`divnum') @result{} divnum(`extra') -@error{}m4:stdin:2: warning: divnum: extra arguments ignored: 1 > 0 +@error{}m4:stdin:2: Warning: excess arguments to builtin `divnum' ignored @error{}m4trace: -1- divnum(`extra') -> `0' @result{}0 debugfile() @result{} divnum(`extra') -@error{}m4:stdin:4: warning: divnum: extra arguments ignored: 1 > 0 +@error{}m4:stdin:4: Warning: excess arguments to builtin `divnum' ignored @result{}0 debugfile @result{} @@ -4750,67 +4117,6 @@ divnum @result{}0 @end example -Although the @option{--safer} option cripples @code{debugfile} to a -limited subset of capabilities, you may still use the @option{--debugfile} -option from the command line with no restrictions. - -@comment options: --safer --debugfile=trace -tfoo -Dfoo=bar -d+l -@comment status: 1 -@example -$ @kbd{m4 --safer --debugfile trace -t foo -D foo=bar -daelq} -foo # traced to `trace' -@result{}bar # traced to `trace' -debugfile(`file') -@error{}m4:stdin:2: debugfile: disabled by --safer -@result{} -foo # traced to `trace' -@result{}bar # traced to `trace' -debugfile() -@result{} -foo # trace discarded -@result{}bar # trace discarded -debugfile -@result{} -foo # traced to stderr -@error{}m4trace:7: -1- foo -> `bar' -@result{}bar # traced to stderr -undivert(`trace')dnl -@result{}m4trace:1: -1- foo -> `bar' -@result{}m4trace:3: -1- foo -> `bar' -@end example - -Sometimes it is useful to post-process trace output, even though there -is no standardized format for trace output. In this situation, forcing -@code{dumpdef} to output to standard error instead of the default of the -current debug file will avoid any ambiguities between the two types of -output; it also allows debugging via @code{dumpdef} when debug output is -discarded. - -@example -$ @kbd{m4 -d} -traceon(`divnum') -@result{} -divnum -@error{}m4trace: -1- divnum -> `0' -@result{}0 -dumpdef(`divnum') -@error{}divnum:@tabchar{}<divnum> -@result{} -debugfile(`') -@result{} -divnum -@result{}0 -dumpdef(`divnum') -@result{} -debugmode(`+o') -@result{} -divnum -@result{}0 -dumpdef(`divnum') -@error{}divnum:@tabchar{}<divnum> -@result{} -@end example - @node Input Control @chapter Input control @@ -4821,8 +4127,7 @@ to @code{m4}. * Dnl:: Deleting whitespace in input * Changequote:: Changing the quote characters * Changecom:: Changing the comment delimiters -* Changeresyntax:: Changing the regular expression syntax -* Changesyntax:: Changing the lexical structure of the input +* Changeword:: Changing the lexical structure of words * M4wrap:: Saving text until end of input @end menu @@ -4834,7 +4139,7 @@ to @code{m4}. @cindex input, discarding The builtin @code{dnl} stands for ``Discard to Next Line'': -@deffn {Builtin (m4)} dnl +@deffn Builtin dnl All characters, up to and including the next newline, are discarded without performing any macro expansion. A warning is issued if the end of the file is encountered without a newline. @@ -4852,12 +4157,10 @@ foo @end example The input up to and including the next newline is discarded, as opposed -to the way comments are treated (@pxref{Comments}), when the command -line option @option{--discard-comments} is not in effect -(@pxref{Operation modes, , Invoking m4}). +to the way comments are treated (@pxref{Comments}). Usually, @code{dnl} is immediately followed by an end of line or some -other whitespace. @acronym{GNU} @code{m4} will produce a warning diagnostic if +other whitespace. GNU @code{m4} will produce a warning diagnostic if @code{dnl} is followed by an open parenthesis. In this case, @code{dnl} will collect and process all arguments, looking for a matching close parenthesis. All predictable side effects resulting from this @@ -4868,7 +4171,7 @@ next newline, on whatever line containing it, will still be discarded. @example dnl(`args are ignored, but side effects occur', define(`foo', `like this')) while this text is ignored: undefine(`foo') -@error{}m4:stdin:1: warning: dnl: extra arguments ignored: 2 > 0 +@error{}m4:stdin:1: Warning: excess arguments to builtin `dnl' ignored See how `foo' was defined, foo? @result{}See how foo was defined, like this? @end example @@ -4883,7 +4186,7 @@ m4wrap(`m4wrap(`2 hi define(`hi', `HI') @result{} ^D -@error{}m4:stdin:1: warning: dnl: end of file treated as newline +@error{}m4:stdin:1: Warning: end of file treated as newline @result{}0 HI 2 HI @end example @@ -4896,7 +4199,7 @@ define(`hi', `HI') The default quote delimiters can be changed with the builtin @code{changequote}: -@deffn {Builtin (m4)} changequote (@dvar{start, `}, @dvar{end, '}) +@deffn Builtin changequote (@dvar{start, `}, @dvar{end, '}) This sets @var{start} as the new begin-quote delimiter and @var{end} as the new end-quote delimiter. If both arguments are missing, the default quotes (@code{`} and @code{'}) are used. If @var{start} is void, then @@ -4917,9 +4220,25 @@ foo @end example The quotation strings can safely contain eight-bit characters. +@ignore +@comment Yuck. I know of no clean way to render an 8-bit character in +@comment both info and dvi. This example uses the `open-guillemot' and +@comment `close-guillemot' characters of the Latin-1 character set. + +@example +define(`a', `b') +@result{} +«a» +@result{}«b» +changequote(`«', `»') +@result{} +«a» +@result{}a +@end example +@end ignore If no single character is appropriate, @var{start} and @var{end} can be of any length. Other implementations cap the delimiter length to five -characters, but @acronym{GNU} has no inherent limit. +characters, but GNU has no inherent limit. @example changequote(`[[[', `]]]') @@ -4970,7 +4289,7 @@ and one for the new quotes. Macros are recognized in preference to the begin-quote string, so if a prefix of @var{start} can be recognized as part of a potential macro name, the quoting mechanism is effectively disabled. Unless you use -@code{changesyntax} (@pxref{Changesyntax}), this means that @var{start} +@code{changeword} (@pxref{Changeword}), this means that @var{start} should not begin with a letter, digit, or @samp{_} (underscore). However, even though quoted strings are not recognized, the quote characters can still be discerned in macro expansion and in trace @@ -5090,6 +4409,18 @@ changequote(`"', `"') @result{}hiHIhi @end example +@ignore +@comment And another stress test, not worth documenting in the manual. +@example +define(`aaaaaaaaaaaaaaaaaaaa', `A')define(`q', `"$@@"') +@result{} +changequote(`"', `"') +@result{} +q(q("aaaaaaaaaaaaaaaaaaaa", "a")) +@result{}A,a +@end example +@end ignore + It is an error if the end of file occurs within a quoted string. @comment status: 1 @@ -5098,14 +4429,14 @@ It is an error if the end of file occurs within a quoted string. @result{}hello world `dangling quote ^D -@error{}m4:stdin:2: end of file in string +@error{}m4:stdin:2: ERROR: end of file in string @end example @comment status: 1 @example ifelse(`dangling quote ^D -@error{}m4:stdin:1: ifelse: end of file in string +@error{}m4:stdin:1: ERROR: end of file in string @end example @node Changecom @@ -5117,7 +4448,7 @@ ifelse(`dangling quote The default comment delimiters can be changed with the builtin macro @code{changecom}: -@deffn {Builtin (m4)} changecom (@ovar{start}, @dvar{end, @key{NL}}) +@deffn Builtin changecom (@ovar{start}, @dvar{end, @key{NL}}) This sets @var{start} as the new begin-comment delimiter and @var{end} as the new end-comment delimiter. If both arguments are missing, or @var{start} is void, then comments are disabled. Otherwise, if @@ -5168,19 +4499,33 @@ changecom(`#', `') @end example The comment strings can safely contain eight-bit characters. +@ignore +@comment Yuck. I know of no clean way to render an 8-bit character in +@comment both info and dvi. This example uses the `open-guillemot' and +@comment `close-guillemot' characters of the Latin-1 character set. + +@example +define(`a', `b') +@result{} +«a» +@result{}«b» +changecom(`«', `»') +@result{} +«a» +@result{}«a» +@end example +@end ignore If no single character is appropriate, @var{start} and @var{end} can be of any length. Other implementations cap the delimiter length to five -characters, but @acronym{GNU} has no inherent limit. +characters, but GNU has no inherent limit. -As of M4 1.6, macros and quotes are recognized in preference to -comments, so if a prefix of @var{start} can be recognized as part of a -potential macro name, or confused with a quoted string, the comment -mechanism is effectively disabled (earlier versions of @acronym{GNU} M4 -favored comments, but this was inconsistent with other implementations). -Unless you use @code{changesyntax} (@pxref{Changesyntax}), this means -that @var{start} should not begin with a letter, digit, or @samp{_} -(underscore), and that neither the start-quote nor the start-comment -string should be a prefix of the other. +Comments are recognized in preference to macros. However, this is not +compatible with other implementations, where macros and even quoting +takes precedence over comments, so it may change in a future release. +For portability, this means that @var{start} should not begin with a +letter, digit, or @samp{_} (underscore), and that neither the +start-quote nor the start-comment string should be a prefix of the +other. @example define(`hi', `HI') @@ -5190,33 +4535,13 @@ define(`hi1hi2', `hello') changecom(`q', `Q') @result{} q hi Q hi -@result{}q HI Q HI +@result{}q hi Q HI changecom(`1', `2') @result{} hi1hi2 @result{}hello hi 1hi2 @result{}HI 1hi2 -changecom(`[[', `]]') -@result{} -changequote(`[[[', `]]]') -@result{} -[hi] -@result{}[HI] -[[hi]] -@result{}[[hi]] -[[[hi]]] -@result{}hi -changequote -@result{} -changecom(`[[[', `]]]') -@result{} -changequote(`[[', `]]') -@result{} -[[hi]] -@result{}hi -[[[hi]]] -@result{}[hi] @end example Comments are recognized in preference to argument collection. In @@ -5262,539 +4587,233 @@ changecom(`/*', `*/') @result{} /*dangling comment ^D -@error{}m4:stdin:2: end of file in comment -@end example - -@comment status: 1 -@example -changecom(`/*', `*/') -@result{} -len(/*dangling comment -^D -@error{}m4:stdin:2: len: end of file in comment -@end example - -@node Changeresyntax -@section Changing the regular expression syntax - -@cindex regular expression syntax, changing -@cindex basic regular expressions -@cindex extended regular expressions -@cindex regular expressions -@cindex expressions, regular -@cindex syntax, changing regular expression -@cindex flavors of regular expressions -@cindex @acronym{GNU} extensions -The @acronym{GNU} extensions @code{patsubst}, @code{regexp}, and more -recently, @code{renamesyms} each deal with regular expressions. There -are multiple flavors of regular expressions, so the -@code{changeresyntax} builtin exists to allow choosing the default -flavor: - -@deffn {Builtin (gnu)} changeresyntax (@var{resyntax}) -Changes the default regular expression syntax used by M4 according to -the value of @var{resyntax}, equivalent to passing @var{resyntax} as the -argument to the command line option @option{--regexp-syntax} -(@pxref{Operation modes, , Invoking m4}). If @var{resyntax} is empty, -the default flavor is reverted to the @code{GNU_M4} style, compatible -with emacs. - -@var{resyntax} can be any one of the values in the table below. Case is -not important, and @samp{-} or @samp{ } can be substituted for @samp{_} in -the given names. If @var{resyntax} is unrecognized, a warning is -issued and the default flavor is not changed. - -@table @dfn -@item AWK -@xref{awk regular expression syntax}, for details. - -@item BASIC -@itemx ED -@itemx POSIX_BASIC -@itemx SED -@xref{posix-basic regular expression syntax}, for details. - -@item BSD_M4 -@item EXTENDED -@itemx POSIX_EXTENDED -@xref{posix-extended regular expression syntax}, for details. - -@item GNU_AWK -@itemx GAWK -@xref{gnu-awk regular expression syntax}, for details. - -@item GNU_EGREP -@itemx EGREP -@xref{egrep regular expression syntax}, for details. - -@item GNU_M4 -@item EMACS -@itemx GNU_EMACS -@xref{emacs regular expression syntax}, for details. This is the -default regular expression flavor. - -@item GREP -@xref{grep regular expression syntax}, for details. - -@item MINIMAL -@itemx POSIX_MINIMAL -@itemx POSIX_MINIMAL_BASIC -@xref{posix-minimal-basic regular expression syntax}, for details. - -@item POSIX_AWK -@xref{posix-awk regular expression syntax}, for details. - -@item POSIX_EGREP -@xref{posix-egrep regular expression syntax}, for details. -@end table - -The expansion of @code{changeresyntax} is void. -The macro @code{changeresyntax} is recognized only with parameters. -This macro was added in M4 2.0. -@end deffn - -For an example of how @var{resyntax} is recognized, the first three -usages select the @samp{GNU_M4} regular expression flavor: - -@example -changeresyntax(`gnu m4') -@result{} -changeresyntax(`GNU-m4') -@result{} -changeresyntax(`Gnu_M4') -@result{} -changeresyntax(`unknown') -@error{}m4:stdin:4: warning: changeresyntax: bad syntax-spec: `unknown' -@result{} -@end example - -Using @code{changeresyntax} makes it possible to omit the optional -@var{resyntax} parameter to other macros, while still using a different -regular expression flavor. - -@example -patsubst(`ab', `a|b', `c') -@result{}ab -patsubst(`ab', `a\|b', `c') -@result{}cc -patsubst(`ab', `a|b', `c', `EXTENDED') -@result{}cc -changeresyntax(`EXTENDED') -@result{} -patsubst(`ab', `a|b', `c') -@result{}cc -patsubst(`ab', `a\|b', `c') -@result{}ab +@error{}m4:stdin:2: ERROR: end of file in comment @end example -@node Changesyntax -@section Changing the lexical structure of the input +@node Changeword +@section Changing the lexical structure of words -@cindex lexical structure of the input -@cindex input, lexical structure of the -@cindex syntax table +@cindex lexical structure of words +@cindex words, lexical structure of +@cindex syntax, changing @cindex changing syntax -@cindex @acronym{GNU} extensions +@cindex regular expressions @quotation -The macro @code{changesyntax} and all associated functionality is -experimental (@pxref{Experiments}). The functionality might change in -the future. Please direct your comments about it the same way you would -do for bugs. +The macro @code{changeword} and all associated functionality is +experimental. It is only available if the @option{--enable-changeword} +option was given to @command{configure}, at GNU @code{m4} +installation +time. The functionality will go away in the future, to be replaced by +other new features that are more efficient at providing the same +capabilities. @emph{Do not rely on it}. Please direct your comments +about it the same way you would do for bugs. @end quotation -The input to @code{m4} is read character by character, and these -characters are grouped together to form input tokens (such as macro -names, strings, comments, etc.). - -Each token is parsed according to certain rules. For example, a macro -name starts with a letter or @samp{_} and consists of the longest -possible string of letters, @samp{_} and digits. But who is to decide -what characters are letters, digits, quotes, white space? Earlier the -operating system decided, now you do. The builtin macro -@code{changesyntax} is used to change the way @code{m4} parses the input -stream into tokens. - -@deffn {Builtin (gnu)} changesyntax (@var{syntax-spec}, @dots{}) -Each @var{syntax-spec} is a two-part string. The first part is a -command, consisting of a single character describing a syntax category, -and an optional one-character action. The action can be @samp{-} to -remove the listed characters from that category, @samp{=} to set the -category to the listed characters -and reassign all other characters previously in that category to -`Other', or @samp{+} to add the listed characters to the category -without affecting other characters. If an action is not specified, but -additional characters are present, then @samp{=} is assumed. - -The remaining characters of each @var{syntax-spec} form the set of -characters to perform the action on for that syntax category. Character -ranges are expanded as for @code{translit} (@pxref{Translit}). To start -the character set with @samp{-}, @samp{+}, or @samp{=}, an action must -be specified. - -If @var{syntax-spec} is just a category, and no action or characters -were specified, then all characters in that category are reset to their -default state. A warning is issued if the category character is not -valid. If @var{syntax-spec} is the empty string, then all categories -are reset to their default state. - -Syntax categories are divided into basic and context. Every input -byte belongs to exactly one basic syntax category. Additionally, any -byte can be assigned to a context category regardless of its current -basic category. Context categories exist because a character can -behave differently when parsed in isolation than when it occurs in -context to close out a token started by another basic category (for -example, @kbd{newline} defaults to the basic category `Whitespace' as -well as the context category `End comment'). - -The following table describes the case-insensitive designation for each -syntax category (the first byte in @var{syntax-spec}), and a description -of what each category controls. - -@multitable @columnfractions .06 .20 .13 .55 -@headitem Code @tab Category @tab Type @tab Description - -@item @kbd{W} @tab @dfn{Words} @tab Basic -@tab Characters that can start a macro name. Defaults to the letters as -defined by the locale, and the character @samp{_}. - -@item @kbd{D} @tab @dfn{Digits} @tab Basic -@tab Characters that, together with the letters, form the remainder of a -macro name. Defaults to the ten digits @samp{0}@dots{}@samp{9}, and any -other digits defined by the locale. - -@item @kbd{S} @tab @dfn{White space} @tab Basic -@tab Characters that should be trimmed from the beginning of each argument to -a macro call. The defaults are space, tab, newline, carriage return, -form feed, and vertical tab, and any others as defined by the locale. - -@item @kbd{(} @tab @dfn{Open parenthesis} @tab Basic -@tab Characters that open the argument list of a macro call. The default is -the single character @samp{(}. - -@item @kbd{)} @tab @dfn{Close parenthesis} @tab Basic -@tab Characters that close the argument list of a macro call. The default -is the single character @samp{)}. - -@item @kbd{,} @tab @dfn{Argument separator} @tab Basic -@tab Characters that separate the arguments of a macro call. The default is -the single character @samp{,}. - -@item @kbd{L} @tab @dfn{Left quote} @tab Basic -@tab The set of characters that can start a single-character quoted string. -The default is the single character @samp{`}. For multiple-character -quote delimiters, use @code{changequote} (@pxref{Changequote}). - -@item @kbd{R} @tab @dfn{Right quote} @tab Context -@tab The set of characters that can end a single-character quoted string. -The default is the single character @samp{'}. For multiple-character -quote delimiters, use @code{changequote} (@pxref{Changequote}). Note -that @samp{'} also defaults to the syntax category `Other', when it -appears in isolation. - -@item @kbd{B} @tab @dfn{Begin comment} @tab Basic -@tab The set of characters that can start a single-character comment. The -default is the single character @samp{#}. For multiple-character -comment delimiters, use @code{changecom} (@pxref{Changecom}). - -@item @kbd{E} @tab @dfn{End comment} @tab Context -@tab The set of characters that can end a single-character comment. The -default is the single character @kbd{newline}. For multiple-character -comment delimiters, use @code{changecom} (@pxref{Changecom}). Note that -newline also defaults to the syntax category `White space', when it -appears in isolation. - -@item @kbd{$} @tab @dfn{Dollar} @tab Context -@tab Characters that can introduce an argument reference in the body of a -macro. The default is the single character @samp{$}. - -@comment FIXME - implement ${10} argument parsing. -@item @kbd{@{} @tab @dfn{Left brace} @tab Context -@tab Characters that introduce an extended argument reference in the body of -a macro immediately after a character in the Dollar category. The -default is the single character @samp{@{}. - -@item @kbd{@}} @tab @dfn{Right brace} @tab Context -@tab Characters that conclude an extended argument reference in the body of a -macro. The default is the single character @samp{@}}. - -@item @kbd{O} @tab @dfn{Other} @tab Basic -@tab Characters that have no special syntactical meaning to @code{m4}. -Defaults to all characters except those in the categories above. - -@item @kbd{A} @tab @dfn{Active} @tab Basic -@tab Characters that themselves, alone, form macro names. This is a -@acronym{GNU} extension, and active characters have lower precedence -than comments. By default, no characters are active. - -@item @kbd{@@} @tab @dfn{Escape} @tab Basic -@tab Characters that must precede macro names for them to be recognized. -This is a @acronym{GNU} extension. When an escape character is defined, -then macros are not recognized unless the escape character is present; -however, the macro name, visible by @samp{$0} in macro definitions, does -not include the escape character. By default, no characters are -escapes. - -@comment FIXME - we should also consider supporting: -@comment @item @kbd{I} @tab @dfn{Ignore} @tab Basic -@comment @tab Characters that are ignored if they appear in -@comment the input; perhaps defaulting to '\0'. -@end multitable - -The expansion of @code{changesyntax} is void. -The macro @code{changesyntax} is recognized only with parameters. Use -this macro with caution, as it is possible to change the syntax in such -a way that no further macros can be recognized by @code{m4}. -This macro was added in M4 2.0. -@end deffn - -With @code{changesyntax} we can modify what characters form a word. For -example, we can make @samp{.} a valid character in a macro name, or even -start a macro name with a number. +A file being processed by @code{m4} is split into quoted strings, words +(potential macro names) and simple tokens (any other single character). +Initially a word is defined by the following regular expression: +@comment ignore @example -define(`test.1', `TEST ONE') -@result{} -define(`1', `one') -@result{} -__file__ -@result{}stdin -test.1 -@result{}test.1 -dnl Add `.' and remove `_'. -changesyntax(`W+.', `W-_') -@result{} -__file__ -@result{}__file__ -test.1 -@result{}TEST ONE -dnl Set words to include numbers. -changesyntax(`W=a-zA-Z0-9_') -@result{} -__file__ -@result{}stdin -test.1 -@result{}test.one -dnl Reset words to default (a-zA-Z_). -changesyntax(`W') -@result{} -__file__ -@result{}stdin -test.1 -@result{}test.1 +[_a-zA-Z][_a-zA-Z0-9]* @end example -Another possibility is to change the syntax of a macro call. +Using @code{changeword}, you can change this regular expression: -@example -define(`test', `$#') -@result{} -test(a, b, c) -@result{}3 -dnl Change macro syntax. -changesyntax(`(<', `,|', `)>') -@result{} -test(a, b, c) -@result{}0(a, b, c) -test<a|b|c> -@result{}3 -@end example +@deffn {Optional builtin} changeword (@var{regex}) +Changes the regular expression for recognizing macro names to be +@var{regex}. If @var{regex} is empty, use +@samp{[_a-zA-Z][_a-zA-Z0-9]*}. @var{regex} must obey the constraint +that every prefix of the desired final pattern is also accepted by the +regular expression. If @var{regex} contains grouping parentheses, the +macro invoked is the portion that matched the first group, rather than +the entire matching string. + +The expansion of @code{changeword} is void. +The macro @code{changeword} is recognized only with parameters. +@end deffn -Leading spaces are always removed from macro arguments in @code{m4}, but -by changing the syntax categories we can avoid it. The use of -@code{format} is an alternative to using a literal tab character. +Relaxing the lexical rules of @code{m4} might be useful (for example) if +you wanted to apply translations to a file of numbers: @example -define(`test', `$1$2$3') -@result{} -test(`a', `b', `c') -@result{}abc -dnl Don't ignore whitespace. -changesyntax(`O 'format(``%c'', `9')` -') +ifdef(`changeword', `', `errprint(` skipping: no changeword support +')m4exit(`77')')dnl +changeword(`[_a-zA-Z0-9]+') @result{} -test(a, b, -c) -@result{}a b -@result{}c +define(`1', `0')1 +@result{}0 @end example -It is possible to redefine the @samp{$} used to indicate macro arguments -in user defined macros. Dollar class syntax elements are copied to the -output if there is no valid expansion. +Tightening the lexical rules is less useful, because it will generally +make some of the builtins unavailable. You could use it to prevent +accidental call of builtins, for example: @example -define(`argref', `Dollar: $#, Question: ?#') -@result{} -argref(1, 2, 3) -@result{}Dollar: 3, Question: ?# -dnl Change argument identifier. -changesyntax(`$?') +ifdef(`changeword', `', `errprint(` skipping: no changeword support +')m4exit(`77')')dnl +define(`_indir', defn(`indir')) @result{} -argref(1,2,3) -@result{}Dollar: $#, Question: 3 -define(`escape', `$?`'1$?1?') +changeword(`_[_a-zA-Z0-9]*') @result{} -escape(foo) -@result{}$?1$foo? -dnl Multiple argument identifiers. -changesyntax(`$+$') +esyscmd(`foo') +@result{}esyscmd(foo) +_indir(`esyscmd', `echo hi') +@result{}hi @result{} -argref(1, 2, 3) -@result{}Dollar: 3, Question: 3 @end example -Macro calls can be given a @TeX{} or Texinfo like syntax using an -escape. If one or more characters are defined as escapes, macro names -are only recognized if preceded by an escape character. - -If the escape is not followed by what is normally a word (a letter -optionally followed by letters and/or numerals), that single character -is returned as a macro name. - -As always, words without a macro definition cause no error message. -They and the escape character are simply output. +Because @code{m4} constructs its words a character at a time, there +is a restriction on the regular expressions that may be passed to +@code{changeword}. This is that if your regular expression accepts +@samp{foo}, it must also accept @samp{f} and @samp{fo}. @example -define(`foo', `bar') -@result{} -dnl Require @@ escape before any macro. -changesyntax(`@@@@') +ifdef(`changeword', `', `errprint(` skipping: no changeword support +')m4exit(`77')')dnl +define(`foo +', `bar +') @result{} +dnl This example wants to recognize changeword, dnl, and `foo\n'. +dnl First, we check that our regexp will match. +regexp(`changeword', `[cd][a-z]*\|foo[ +]') +@result{}0 +regexp(`foo +', `[cd][a-z]*\|foo[ +]') +@result{}0 +regexp(`f', `[cd][a-z]*\|foo[ +]') +@result{}-1 foo @result{}foo -@@foo -@result{}bar -@@bar -@result{}@@bar -@@dnl Change escape character. -@@changesyntax(`@@\', `O@@') +changeword(`[cd][a-z]*\|foo[ +]') @result{} +dnl Even though `foo\n' matches, we forgot to allow `f'. foo @result{}foo -@@foo -@result{}@@foo -\foo -@result{}bar -define(`#', `No comment') -@result{}define(#, No comment) -\define(`#', `No comment') +changeword(`[cd][a-z]*\|fo*[ +]?') @result{} -\# \foo # Comment \foo -@result{}No comment bar # Comment \foo +dnl Now we can call `foo\n'. +foo +@result{}bar @end example -Active characters are known from @TeX{}. In @code{m4} an active -character is always seen as a one-letter word, and so, if it has a macro -definition, the macro will be called. +@ignore +@comment One more test of including newline in a macro name; but this +@comment does not need to be displayed in the manual. This ensures +@comment that line numbering is correct when dnl cuts across include +@comment file boundaries, and when __file__ or __line__ is the last +@comment token in an include file. @example -define(`@@', `TEST') -@result{} -define(`a@@a', `hello') -@result{} -define(`a', `A') +ifdef(`changeword', `', `errprint(` skipping: no changeword support +')m4exit(`77')')dnl +define(`bar +', defn(`dnl'))dnl +define(`baz', `dnl +include(`foo') ignored +dnl')dnl +changeword(`\([_a-zA-Z][_a-zA-Z0-9]*\|bar +\)') +@result{} +__file__:__line__ +@result{}stdin:10 +include(`foo') ignored +__file__:__line__ +@result{}stdin:12 +baz ignored +__file__:__line__ +@result{}stdin:14 +define(`bar +', defn(`__file__')) @result{} -@@ -@result{}@@ -a@@a -@result{}A@@A -dnl Make @@ active. -changesyntax(`A@@') +include(`foo') +@result{}examples/foo +define(`bar +', defn(`__line__')) @result{} -@@ -@result{}TEST -a@@a -@result{}ATESTa +include(`foo') +@result{}1 +__file__:__line__ +@result{}stdin:21 @end example +@end ignore -There is obviously an overlap between @code{changesyntax} and -@code{changequote}, since there are now two ways to modify quote -delimiters. To avoid incompatibilities, if the quotes are modified by -@code{changequote}, any characters previously set to either quote -delimiter by @code{changesyntax} are first demoted to the other category -(@samp{O}), so the result is only a single set of quotes. In the other -direction, if quotes were already disabled, or if both the start and end -delimiter set by @code{changequote} are single bytes, then -@code{changesyntax} preserves those settings. But if either delimiter -occupies multiple bytes, @code{changesyntax} first disables both -delimiters. Quotes can be disabled via @code{changesyntax} by emptying -the left quote basic category (@samp{L}). Meanwhile, the right quote -context category (@samp{R}) will never be empty; if a -@code{changesyntax} action would otherwise leave that category empty, -then the default end delimiter from @code{changequote} (@samp{'}) is -used; thus, it is never possible to get @code{m4} in a state where a -quoted string cannot be terminated. These interactions apply to comment -delimiters as well, @i{mutatis mutandis} with @code{changecom}. +@code{changeword} has another function. If the regular expression +supplied contains any grouped subexpressions, then text outside +the first of these is discarded before symbol lookup. So: @example -define(`test', `TEST') -@result{} -dnl Add additional single-byte delimiters. -changesyntax(`L+<', `R+>') -@result{} -<test> `test' [test] <<test>> -@result{}test test [TEST] <test> -dnl Use standard interface, overriding changesyntax settings. -changequote(<[>, `]') -@result{} -<test> `test' [test] <<test>> -@result{}<TEST> `TEST' test <<TEST>> -dnl Introduce multi-byte delimiters. -changequote([<<], [>>]) -@result{} -<test> `test' [test] <<test>> -@result{}<TEST> `TEST' [TEST] test -dnl Change end quote, effectively disabling quotes. -changesyntax(<<R]>>) -@result{} -<test> `test' [test] <<test>> -@result{}<TEST> `TEST' [TEST] <<TEST>> -dnl Change beginning quote, make ] normal, thus making ' end quote. -changesyntax(L`, R-]) +ifdef(`changeword', `', `errprint(` skipping: no changeword support +')m4exit(`77')')dnl +ifdef(`__unix__', , + `errprint(` skipping: syscmd does not have unix semantics +')m4exit(`77')')dnl +changecom(`/*', `*/')dnl +define(`foo', `bar')dnl +changeword(`#\([_a-zA-Z0-9]*\)') @result{} -<test> `test' [test] <<test>> -@result{}<TEST> test [TEST] <<TEST>> -dnl Set multi-byte quote; unrelated changes don't impact it. -changequote(`<<', `>>')changesyntax(<<@@\>>) +#esyscmd(`echo foo \#foo') +@result{}foo bar @result{} -<\test> `\test' [\test] <<\test>> -@result{}<TEST> `TEST' [TEST] \test @end example -If several characters are assigned to a category that forms single -character tokens, all such characters are treated as equal. Any open -parenthesis will match any close parenthesis, etc. +@code{m4} now requires a @samp{#} mark at the beginning of every +macro invocation, so one can use @code{m4} to preprocess plain +text without losing various words like @samp{divert}. + +In @code{m4}, macro substitution is based on text, while in @TeX{}, it +is based on tokens. @code{changeword} can throw this difference into +relief. For example, here is the same idea represented in @TeX{} and +@code{m4}. First, the @TeX{} version: +@comment ignore @example -dnl Go crazy with symbols. -changesyntax(`(@{<', `)@}>', `,;:', `O(,)') -@result{} -eval@{2**4-1; 2: 8> -@result{}00001111 +\def\a@{\message@{Hello@}@} +\catcode`\@@=0 +\catcode`\\=12 +@@a +@@bye +@result{}Hello @end example -The syntax table is initialized to be backwards compatible, so if you -never call @code{changesyntax}, nothing will have changed. - -For now, debugging output continues to use @kbd{(}, @kbd{,} and @kbd{)} -to show macro calls; and macro expansions that result in a list of -arguments (such as @samp{$@@} or @code{shift}) use @samp{,}, regardless -of the current syntax settings. However, this is likely to change in a -future release, so it should not be relied on, particularly since it is -next to impossible to write recursive macros if the argument separator -doesn't match between expansion and rescanning. +@noindent +Then, the @code{m4} version: -@c FIXME - changing syntax of , should not break iterative macros. @example -$ @kbd{m4 -d} -changesyntax(`,=|')traceon(`foo')define(`foo'|`$#:$@@') +ifdef(`changeword', `', `errprint(` skipping: no changeword support +')m4exit(`77')')dnl +define(`a', `errprint(`Hello')')dnl +changeword(`@@\([_a-zA-Z0-9]*\)') @result{} -foo(foo(1|2|3)) -@error{}m4trace: -2- foo(`1', `2', `3') -> `3:`1',`2',`3'' -@error{}m4trace: -1- foo(`3:1,2,3') -> `1:`3:1,2,3'' -@result{}1:3:1,2,3 +@@a +@result{}errprint(Hello) @end example +In the @TeX{} example, the first line defines a macro @code{a} to +print the message @samp{Hello}. The second line defines @key{@@} to +be usable instead of @key{\} as an escape character. The third line +defines @key{\} to be a normal printing character, not an escape. +The fourth line invokes the macro @code{a}. So, when @TeX{} is run +on this file, it displays the message @samp{Hello}. + +When the @code{m4} example is passed through @code{m4}, it outputs +@samp{errprint(Hello)}. The reason for this is that @TeX{} does +lexical analysis of macro definition when the macro is @emph{defined}. +@code{m4} just stores the text, postponing the lexical analysis until +the macro is @emph{used}. + +You should note that using @code{changeword} will slow @code{m4} down +by a factor of about seven, once it is changed to something other +than the default regular expression. You can invoke @code{changeword} +with the empty string to restore the default word definition, and regain +the parsing speed. + @node M4wrap @section Saving text until end of input @@ -5810,14 +4829,11 @@ files. To save input text, use the builtin @code{m4wrap}: -@deffn {Builtin (m4)} m4wrap (@var{string}, @dots{}) +@deffn Builtin m4wrap (@var{string}, @dots{}) Stores @var{string} in a safe place, to be reread when end of input is -reached. As a @acronym{GNU} extension, additional arguments are +reached. As a GNU extension, additional arguments are concatenated with a space to the @var{string}. -Successive invocations of @code{m4wrap} accumulate saved text in -first-in, first-out order, as required by @acronym{POSIX}. - The expansion of @code{m4wrap} is void. The macro @code{m4wrap} is recognized only with parameters. @end deffn @@ -5837,28 +4853,19 @@ This is the first and last normal input line. The saved input is only reread when the end of normal input is seen, and not if @code{m4exit} is used to exit @code{m4}. -It is safe to call @code{m4wrap} from wrapped text, where all the -recursively wrapped text is deferred until the current wrapped text is -exhausted. As of M4 1.6, when @code{m4wrap} is not used recursively, -the saved pieces of text are reread in the same order in which they were -saved (FIFO---first in, first out), as required by @acronym{POSIX}. - -@example -m4wrap(`1 -') -@result{} -m4wrap(`2', `3 -') -@result{} -^D -@result{}1 -@result{}2 3 -@end example - -However, earlier versions had reverse ordering (LIFO---last in, first -out), as this behavior is more like the semantics of the C function -@code{atexit}. It is possible to emulate @acronym{POSIX} behavior even -with older versions of @acronym{GNU} M4 by including the file +@comment FIXME: this contradicts POSIX, which requires that "If the +@comment m4wrap macro is used multiple times, the arguments specified +@comment shall be processed in the order in which the m4wrap macros were +@comment processed." +It is safe to call @code{m4wrap} from saved text, but then the order in +which the saved text is reread is undefined. If @code{m4wrap} is not used +recursively, the saved pieces of text are reread in the opposite order +in which they were saved (LIFO---last in, first out). However, this +behavior is likely to change in a future release, to match +POSIX, so you should not depend on this order. + +It is possible to emulate POSIX behavior even +with older versions of GNU M4 by including the file @file{m4-@value{VERSION}/@/examples/@/wrapfifo.m4} from the distribution: @@ -5886,7 +4893,7 @@ m4wrap(`a`'m4wrap(`c @end example It is likewise possible to emulate LIFO behavior without resorting to -the @acronym{GNU} M4 extension of @code{builtin}, by including the file +the GNU M4 extension of @code{builtin}, by including the file @file{m4-@value{VERSION}/@/examples/@/wraplifo.m4} from the distribution. (Unfortunately, both examples shown here share some subtle bugs. See if you can find and correct them; or @pxref{Improved @@ -5933,13 +4940,13 @@ Invocations of @code{m4wrap} at the same recursion level are concatenated and rescanned as usual: @example -define(`ab', `AB +define(`aa', `AA ') @result{} -m4wrap(`a')m4wrap(`b') +m4wrap(`a')m4wrap(`a') @result{} ^D -@result{}AB +@result{}AA @end example @noindent @@ -5951,25 +4958,7 @@ file condition between two input files. m4wrap(`m4wrap(`)')len(abc') @result{} ^D -@error{}m4:stdin:1: len: end of file in argument list -@end example - -As of M4 1.6, @code{m4wrap} transparently handles builtin tokens -generated by @code{defn} (@pxref{Defn}). However, for portability, it -is better to defer the evaluation of @code{defn} along with the rest of -the wrapped text, as is done for @code{foo} in the example below, rather -than computing the builtin token up front, as is done for @code{bar}. - -@example -m4wrap(`define(`foo', defn(`divnum'))foo -') -@result{} -m4wrap(`define(`bar', ')m4wrap(defn(`divnum'))m4wrap(`)bar -') -@result{} -^D -@result{}0 -@result{}0 +@error{}m4:stdin:1: ERROR: end of file in argument list @end example @node File Inclusion @@ -5989,8 +4978,8 @@ m4wrap(`define(`bar', ')m4wrap(defn(`divnum'))m4wrap(`)bar There are two builtin macros in @code{m4} for including files: -@deffn {Builtin (m4)} include (@var{file}) -@deffnx {Builtin (m4)} sinclude (@var{file}) +@deffn Builtin include (@var{file}) +@deffnx Builtin sinclude (@var{file}) Both macros cause the file named @var{file} to be read by @code{m4}. When the end of the file is reached, input is resumed from the previous input file. @@ -6009,22 +4998,22 @@ parameters. @comment status: 1 @example -include(`n') -@error{}m4:stdin:1: include: cannot open `n': No such file or directory +include(`none') +@error{}m4:stdin:1: cannot open `none': No such file or directory @result{} include() -@error{}m4:stdin:2: include: cannot open `': No such file or directory +@error{}m4:stdin:2: cannot open `': No such file or directory @result{} -sinclude(`n') +sinclude(`none') @result{} sinclude() @result{} @end example -This section uses the @option{--include} command-line option (or -@option{-I}, @pxref{Preprocessor features, , Invoking m4}) to grab -files from the @file{m4-@value{VERSION}/@/examples} -directory shipped as part of the @acronym{GNU} @code{m4} package. The +The rest of this section assumes that @code{m4} is invoked with the +@option{-I} option (@pxref{Preprocessor features, , Invoking m4}) +pointing to the @file{m4-@value{VERSION}/@/examples} +directory shipped as part of the GNU @code{m4} package. The file @file{m4-@value{VERSION}/@/examples/@/incl.m4} in the distribution contains the lines: @@ -6071,22 +5060,58 @@ This is `bar': >>bar<< This use of @code{include} is not trivial, though, as files can contain quotes, commas, and parentheses, which can interfere with the way the -@code{m4} parser works. @acronym{GNU} @code{m4} seamlessly concatenates +@code{m4} parser works. GNU @code{m4} seamlessly concatenates the file contents with the next character, even if the included file ended in the middle of a comment, string, or macro call. These conditions are only treated as end of file errors if specified as input files on the command line. -In @acronym{GNU} @code{m4}, an alternative method of reading files is +In GNU @code{m4}, an alternative method of reading files is using @code{undivert} (@pxref{Undivert}) on a named file. +@ignore +@comment Test that include(`file/') detects that file is not a +@comment directory; we can assume that the current directory contains a +@comment Makefile. mingw fails with EINVAL rather than ENOTDIR. + +@comment status: 1 +@comment xerr: ignore +@example +include(`Makefile/') +@error{}m4:stdin:1: cannot open `Makefile/': Not a directory +@result{} +@end example + +@comment POSIX allows, but doesn't require, failure on reading +@comment directories. But since they aren't text files, it never makes +@comment sense, so we globally forbid it even if fopen doesn't. mingw +@comment fails with EACCES rather than EISDIR. + +@comment status: 1 +@comment xerr: ignore +@example +include(`.') +@error{}m4:stdin:1: cannot open `.': Is a directory +@result{} +@end example + +@comment Meanwhile, ignore errors with sinclude. + +@example +sinclude(`Makefile/') +@result{} +sinclude(`.') +@result{} +@end example +@end ignore + @node Search Path @section Searching for include files @cindex search path for included files @cindex included files, search path for -@cindex @acronym{GNU} extensions -@acronym{GNU} @code{m4} allows included files to be found in other directories +@cindex GNU extensions +GNU @code{m4} allows included files to be found in other directories than the current working directory. @cindex @env{M4PATH} @@ -6101,7 +5126,7 @@ it is expected to contain a colon-separated list of directories, which will be searched in order. If the automatic search for include-files causes trouble, the @samp{p} -debug flag (@pxref{Debugmode}) can help isolate the problem. +debug flag (@pxref{Debug Levels}) can help isolate the problem. @node Diversions @chapter Diverting and undiverting output @@ -6114,7 +5139,7 @@ time. @cindex @env{TMPDIR} Numbered diversions are counted from 0 upwards, diversion number 0 -being the normal output stream. @acronym{GNU} +being the normal output stream. GNU @code{m4} tries to keep diversions in memory. However, there is a limit to the overall memory usable by all diversions taken together (512K, currently). When this maximum is about to be exceeded, @@ -6125,9 +5150,111 @@ environment variable @env{TMPDIR}, and falls back to @file{/tmp}. Thus, the amount of available disk space provides the only real limit on the number and aggregate size of diversions. +@ignore +@comment We need to test spilled diversions, but don't need to expose +@comment this highly repetitive test in the manual. + +@example +divert(`-1')define(`f', `.') +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +divert`'dnl +len(f) +@result{}1048576 +divert(`1') +f +divert(`2') +f +divert(`-1')undivert +divert(`1')bye +^D +@result{}bye +@end example + +@comment Another test of spilled diversions. + +@example +divert(`-1')define(`f', `.') +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +define(`f', defn(`f')defn(`f')) +divert`'dnl +len(f) +@result{}1048576 +divert(`1') +f +m4exit +@end example + +@comment Catch regression in 1.4.10 with spilled diversions. + +@example +ifdef(`__unix__', , + `errprint(` skipping: syscmd does not have unix semantics +')m4exit(`77')')dnl +changequote(`[', `]')dnl +syscmd([echo 'divert(1)hi +format(%1000000d, 1)' | ']__program__[' | sed -n 1p])dnl +@result{}hi +sysval +@result{}0 +@end example + +@comment Avoid quadratic copying time when transferring diversions; +@comment test both in-memory and spilled to file. + +@comment examples +@example +$ @kbd{m4 -I examples} +include(`forloop2.m4')dnl +divert(`1')format(`%10000s', `')dnl +forloop(`i', `1', `10000', + `divert(incr(i))undivert(i)')dnl +divert(`9001')format(`%1000000s', `')dnl +forloop(`i', `9001', `10000', + `divert(incr(i))undivert(i)')dnl +divert(`-1')undivert +@end example +@end ignore + Diversions make it possible to generate output in a different order than the input was read. It is possible to implement topological sorting -dependencies. For example, @acronym{GNU} Autoconf makes use of +dependencies. For example, GNU Autoconf makes use of diversions under the hood to ensure that the expansion of a prerequisite macro appears in the output prior to the expansion of a dependent macro, regardless of which order the two macros were invoked in the user's @@ -6148,17 +5275,11 @@ input file. @cindex files, diverting output to Output is diverted using @code{divert}: -@deffn {Builtin (m4)} divert (@dvar{number, 0}, @ovar{text}) +@deffn Builtin divert (@dvar{number, 0}) The current diversion is changed to @var{number}. If @var{number} is left out or empty, it is assumed to be zero. If @var{number} cannot be parsed, the diversion is unchanged. -@cindex @acronym{GNU} extensions -As a @acronym{GNU} extension, if optional @var{text} is supplied and -@var{number} was valid, then @var{text} is immediately output to the -new diversion, regardless of whether the expansion of @code{divert} -occurred while collecting arguments for another macro. - The expansion of @code{divert} is void. @end deffn @@ -6208,9 +5329,9 @@ divert @result{} @end example -@cindex @acronym{GNU} extensions +@cindex GNU extensions Traditional implementations only supported ten diversions. But as a -@acronym{GNU} extension, diversion numbers can be as large as positive +GNU extension, diversion numbers can be as large as positive integers will allow, rather than treating a multi-digit diversion number as a request to discard text. @@ -6222,44 +5343,6 @@ divert(`2')hello @result{}world @end example -The ability to immediately output extra text is a @acronym{GNU} -extension, but it can prove useful for ensuring that text goes to a -particular diversion no matter how many pending macro expansions are in -progress. For a demonstration of why this is useful, it is important to -understand in the example below why @samp{one} is output in diversion 2, -not diversion 1, while @samp{three} and @samp{five} both end up in the -correctly numbered diversion. The key point is that when @code{divert} -is executed unquoted as part of the argument collection of another -macro, the side effect takes place immediately, but the text @samp{one} -is not passed to any diversion until after the @samp{divert(`2')} and -the enclosing @code{echo} have also taken place. The example with -@samp{three} shows how following the quoting rule of thumb delays the -invocation of @code{divert} until it is not nested in any argument -collection context, while the example with @samp{five} shows the use of -the optional argument to speed up the output process. - -@example -define(`echo', `$1') -@result{} -echo(divert(`1')`one'divert(`2'))`'dnl -echo(`divert(`3')three`'divert(`4')')`'dnl -echo(divert(`5', `five')divert(`6'))`'dnl -divert -@result{} -undivert(`1') -@result{} -undivert(`2') -@result{}one -undivert(`3') -@result{}three -undivert(`4') -@result{} -undivert(`5') -@result{}five -undivert(`6') -@result{} -@end example - Note that @code{divert} is an English word, but also an active macro without arguments. When processing plain text, the word might appear in normal text and be unintentionally swallowed as a macro invocation. One @@ -6286,15 +5369,15 @@ We decided to divert the stream for irrigation. Diverted text can be undiverted explicitly using the builtin @code{undivert}: -@deffn {Builtin (m4)} undivert (@ovar{diversions@dots{}}) +@deffn Builtin undivert (@ovar{diversions@dots{}}) Undiverts the numeric @var{diversions} given by the arguments, in the order given. If no arguments are supplied, all diversions are undiverted, in numerical order. @cindex file inclusion @cindex inclusion, of files -@cindex @acronym{GNU} extensions -As a @acronym{GNU} extension, @var{diversions} may contain non-numeric +@cindex GNU extensions +As a GNU extension, @var{diversions} may contain non-numeric strings, which are treated as the names of files to copy into the output without expansion. A warning is issued if a file could not be opened. @@ -6371,28 +5454,23 @@ rearranged among the other diversions. divert(`1')one divert(`2')two divert(`3')three -divert(`4')four -divert(`5')five -divert(`2')undivert(`5', `2', `4')dnl -undivert`'dnl effectively undivert(`1', `2', `3', `4', `5') +divert(`2')undivert`'dnl divert`'undivert`'dnl @result{}two -@result{}five -@result{}four @result{}one @result{}three @end example -@cindex @acronym{GNU} extensions +@cindex GNU extensions @cindex file inclusion @cindex inclusion, of files -@acronym{GNU} @code{m4} allows named files to be undiverted. Given a +GNU @code{m4} allows named files to be undiverted. Given a non-numeric argument, the contents of the file named will be copied, uninterpreted, to the current output. This complements the builtin @code{include} (@pxref{Include}). To illustrate the difference, assume the file @file{foo} contains: -@comment file: foo +@comment ignore @example $ @kbd{cat foo} bar @@ -6434,7 +5512,7 @@ undivert(`1', `2', `foo', `3')dnl @cindex diversion numbers The current diversion is tracked by the builtin @code{divnum}: -@deffn {Builtin (m4)} divnum +@deffn Builtin divnum Expands to the number of the current diversion. @end deffn @@ -6494,343 +5572,6 @@ diversions, given by the arguments. (This macro has a nasty bug! You should try to see if you can find it and correct it; or @pxref{Improved cleardivert, , Answers}). -@node Modules -@chapter Extending M4 with dynamic runtime modules - -@cindex modules -@cindex dynamic modules -@cindex loadable modules -@acronym{GNU} M4 1.4.x had a monolithic architecture. All of its -functionality was contained in a single binary, and additional macros -could be added only by writing more code in the M4 language, or at the -extreme by hacking the sources and recompiling the whole thing to make -a custom M4 installation. - -Starting with release 2.0, M4 uses Libtool's @code{libltdl} facilities -(@pxref{Using libltdl, , libltdl, libtool, The GNU Libtool Manual}) -to move all of M4's builtins out to pluggable modules. Unless compile -time options are set to change the default build, the installed M4 2.0 -binary is virtually identical to 1.4.x, supporting the same builtins. -However, an optional module can be loaded into the running M4 interpreter -to provide a new @code{load} builtin. This facilitates runtime -extension of the M4 builtin macro list using compiled C code linked -against a new shared library, typically named @file{libm4.so}. - -For example, you might want to add a @code{setenv} builtin to M4, to -use before invoking @code{esyscmd}. We might write a @file{setenv.c} -something like this: - -@comment ignore -@example -#include "m4module.h" - -M4BUILTIN(setenv); - -m4_builtin m4_builtin_table[] = -@{ - /* name handler flags minargs maxargs */ - @{ "setenv", builtin_setenv, M4_BUILTIN_BLIND, 2, 3 @}, - - @{ NULL, NULL, 0, 0, 0 @} -@}; - -/** - * setenv(NAME, VALUE, [OVERWRITE]) - **/ -M4BUILTIN_HANDLER (setenv) -@{ - int overwrite = 1; - - if (argc >= 4) - if (!m4_numeric_arg (context, argc, argv, 3, &overwrite)) - return; - - setenv (M4ARG (1), M4ARG (2), overwrite); -@} -@end example - -Then, having compiled and linked the module, in (somewhat contrived) -M4 code: - -@comment ignore -@example -$ @kbd{M4MODPATH=`pwd` m4 --load-module=setenv} -setenv(`PATH', `/sbin:/bin:/usr/sbin:/usr/bin') -@result{} -esyscmd(`ifconfig -a')dnl -@result{}@dots{} -@end example - -Or instead of loading the module from the M4 invocation, you can use -the new @code{load} builtin: - -@comment ignore -@example -$ @kbd{M4MODPATH=`pwd` m4 --load-module=load} -load(`setenv') -@result{} -setenv(`PATH', `/sbin:/bin:/usr/sbin:/usr/bin') -@result{} -@end example - -Also, at build time, you can choose which modules to build into -the core (so that they will be available without dynamic loading). -SUSv3 M4 functionality is contained in the module @samp{m4}, @acronym{GNU} -extensions in the module @samp{gnu}, the @code{load} builtin in the -module @samp{load} and so on. - -We hinted earlier that the @code{m4} and @code{gnu} modules are -preloaded into the installed M4 binary, but it is possible to install -a @emph{thinner} binary; for example, omitting the @acronym{GNU} -extensions by configuring the distribution with @kbd{./configure ---with-modules=m4}. For a binary built with that option to understand -code that uses @acronym{GNU} extensions, you must then run @kbd{m4 ---load-module=gnu}. It is also possible to build a @emph{fatter} -binary with additional modules preloaded: adding, say, the @code{load} -builtin using @kbd{./configure --with-modules="m4 gnu load"}. - -@acronym{GNU} M4 now has a facility for defining additional builtins without -recompiling the sources. In actual fact, all of the builtins provided -by @acronym{GNU} M4 are loaded from such modules. All of the builtin -descriptions in this manual are annotated with the module from which -they are loaded -- mostly from the module @samp{m4}. - -When you start @acronym{GNU} M4, the modules @samp{m4} and @samp{gnu} are -loaded by default. If you supply the @option{-G} option at startup, the -module @samp{traditional} is loaded instead of @samp{gnu}. -@xref{Compatibility}, for more details on the differences between these -two modes of startup. - -@menu -* M4modules:: Listing loaded modules -* Load:: Loading additional modules -* Unload:: Removing loaded modules -* Refcount:: Tracking module references -* Standard Modules:: Standard bundled modules -@end menu - -@node M4modules -@section Listing loaded modules - -@deffn {Builtin (load)} m4modules -Expands to a quoted ordered list of currently loaded modules, -with the most recently loaded module at the front of the list. Loading -a module multiple times will not affect the order of this list, the -position depends on when the module was @emph{first} loaded. -@end deffn - -For example, if @acronym{GNU} @code{m4} is started with the -@option{-m load} option to load the module @samp{load} and make this -builtin available, @code{m4modules} will yield the following: - -@comment options: -m load -@example -$ @kbd{m4 -m load} -m4modules -@result{}load,gnu,m4 -@end example - -@node Load -@section Loading additional modules - -@deffn {Builtin (load)} load (@var{module-name}) -@var{module-name} will be searched for along the module search path -(@pxref{Standard Modules}) and loaded if found. Loading a module -consists of running its initialization function (if any) and then adding -any macros it provides to the internal table. - -The macro @code{load} is recognized only with parameters. -@end deffn - -Once the @code{load} module has successfully loaded, use of the -@samp{load} macro is entirely equivalent to the @option{-m} command line -option. - -@c The -mmpeval/--unload=mpeval pair allows the testsuite to skip this -@c test if mpeval was not configured for usage. -@comment options: -m load -m mpeval --unload-module=mpeval -@example -$ @kbd{m4 -m load} -m4modules -@result{}load,gnu,m4 -load(`mpeval') -@result{} -m4modules -@result{}mpeval,load,gnu,m4 -@end example - -@node Unload -@section Removing loaded modules - -@deffn {Builtin (load)} unload (@var{module-name}) -Any loaded modules that can be listed by the @code{m4modules} macro can be -removed by naming them as the @var{module-name} parameter of the -@code{unload} macro. Unloading a module consists of removing all of the -macros it provides from the internal table of visible macros, and -running the module's finalization method (if any). - -The macro @code{unload} is recognized only with parameters. -@end deffn - -@comment options: -m mpeval -m load -@example -$ @kbd{m4 -m mpeval -m load} -m4modules -@result{}load,mpeval,gnu,m4 -unload(`mpeval') -@result{} -m4modules -@result{}load,gnu,m4 -@end example - -@node Refcount -@section Tracking module references - -@deffn {Builtin (load)} refcount (@var{module-name}) -This macro expands to an integer representing the number of times -@var{module-name} has been loaded but not yet unloaded. No warning is -issued, even if @var{module-name} does not represent a valid module. - -The macro @code{refcount} is recognized only with parameters. -@end deffn - -This example demonstrates tracking the reference count of the gnu -module. - -@comment options: -m load -@example -$ @kbd{m4 -m load} -m4modules -@result{}load,gnu,m4 -refcount(`gnu') -@result{}1 -m4modules -@result{}load,gnu,m4 -load(`gnu') -@result{} -refcount(`gnu') -@result{}2 -unload(`gnu') -@result{} -m4modules -@result{}load,gnu,m4 -refcount(`gnu') -@result{}1 -unload(`gnu') -@result{} -m4modules -@result{}load,m4 -refcount(`gnu') -@result{}0 -refcount(`NoSuchModule') -@result{}0 -@end example - -@node Standard Modules -@section Standard bundled modules - -@acronym{GNU} @code{m4} ships with several bundled modules as standard. -By convention, these modules define a text macro that can be tested -with @code{ifdef} when they are loaded; only the @code{m4} module lacks -this feature test macro, since it is not permitted by @acronym{POSIX}. -Each of the feature test macros are intended to be used without -arguments. - -@table @code -@item m4 -Provides all of the builtins defined by @acronym{POSIX}. This module -is always loaded --- @acronym{GNU} @code{m4} would only be a very slow -version of @command{cat} without the builtins supplied by this module. - -@item gnu -Provides all of the @acronym{GNU} extensions, as defined by -@acronym{GNU} M4 through the 1.4.x release series. It also provides a -couple of feature test macros: - -@deffn {Macro (gnu)} __gnu__ -Expands to the empty string, as an indication that the @samp{gnu} -module is loaded. -@end deffn - -@deffn {Macro (gnu)} __m4_version__ -Expands to an unquoted string containing the release version number of -the running @acronym{GNU} @code{m4} executable. -@end deffn - -This module is always loaded, unless the @option{-G} command line -option is supplied at startup (@pxref{Limits control, , Invoking m4}). - -@item traditional -This module provides compatibility with System V @code{m4}, for anything -not specified by @acronym{POSIX}, and is loaded instead of the -@samp{gnu} module if the @option{-G} command line option is specified. - -@deffn {Macro (traditional)} __traditional__ -Expands to the empty string, as an indication that the -@samp{traditional} module is loaded. -@end deffn - -@item load -This module supplies the builtins required to use modules from within a -@acronym{GNU} @code{m4} program. @xref{Modules}, for more details. The -module also defines the following macro: - -@deffn {Macro (load)} __load__ -Expands to the empty string, as an indication that the @samp{load} -module is loaded. -@end deffn - -@item mpeval -This module provides the implementation for the experimental -@code{mpeval} feature. If the host machine does not have the -@acronym{GNU} gmp library, the builtin will generate an error if called. -@xref{Mpeval}, for more details. The module also defines the following -macro: - -@deffn {Macro (mpeval)} __mpeval__ -Expands to the empty string, as an indication that the @samp{mpeval} -module is loaded. -@end deffn -@end table - -Here is an example of using the feature test macros. - -@example -$ @kbd{m4} -__gnu__-__traditional__ -@result{}-__traditional__ -ifdef(`__gnu__', `Extensions are active', `Minimal features') -@result{}Extensions are active -__gnu__(`ignored') -@error{}m4:stdin:3: warning: __gnu__: extra arguments ignored: 1 > 0 -@result{} -@end example - -@comment options: -G -@example -$ @kbd{m4 --traditional} -__gnu__-__traditional__ -@result{}__gnu__- -ifdef(`__gnu__', `Extensions are active', `Minimal features') -@result{}Minimal features -@end example - -Since the version string is unquoted and can potentially contain macro -names (for example, a beta release could be numbered @samp{1.9b}), or be -impacted by the use of @code{changesyntax}), the -@code{__m4_version__} macro should generally be used via @code{defn} -rather than directly invoked (@pxref{Defn}). In general, feature tests -are more reliable than version number checks, so exercise caution when -using this macro. - -@comment This test is excluded from the testsuite since it depends on a -@comment texinfo macro; but builtins.at covers the same thing. -@comment ignore -@example -defn(`__m4_version__') -@result{}@value{VERSION} -@end example - @node Text handling @chapter Macros for text handling @@ -6854,7 +5595,7 @@ various ways, extracting substrings, searching, substituting, and so on. @cindex strings, length of The length of a string can be calculated by @code{len}: -@deffn {Builtin (m4)} len (@var{string}) +@deffn Builtin len (@var{string}) Expands to the length of @var{string}, as a decimal number. The macro @code{len} is recognized only with parameters. @@ -6873,13 +5614,11 @@ len(`abcdef') @cindex substrings, locating Searching for substrings is done with @code{index}: -@deffn {Builtin (m4)} index (@var{string}, @var{substring}, @ovar{offset}) +@deffn Builtin index (@var{string}, @var{substring}) Expands to the index of the first occurrence of @var{substring} in @var{string}. The first character in @var{string} has index 0. If @var{substring} does not occur in @var{string}, @code{index} expands to -@samp{-1}. If @var{offset} is provided, it determines the index at -which the search starts; a negative @var{offset} specifies the offset -relative to the end of @var{string}. +@samp{-1}. The macro @code{index} is recognized only with parameters. @end deffn @@ -6896,7 +5635,7 @@ contrast this with an empty @var{substring}. @example index(`abc') -@error{}m4:stdin:1: warning: index: too few arguments: 1 < 2 +@error{}m4:stdin:1: Warning: too few arguments to builtin `index' @result{}0 index(`abc', `') @result{}0 @@ -6904,43 +5643,50 @@ index(`abc', `b') @result{}1 @end example -@cindex @acronym{GNU} extensions -As an extension, an @var{offset} can be provided to limit the search to -the tail of the @var{string}. A negative offset is interpreted relative -to the end of @var{string}, and it is not an error if @var{offset} -exceeds the bounds of @var{string}. +@ignore +@comment Expose a bug in the strstr() algorithm present in glibc +@comment 2.9 through 2.12 and in gnulib up to Sep 2010. @example -index(`aba', `a', `1') -@result{}2 -index(`ababa', `ba', `-3') -@result{}3 -index(`abc', `ab', `4') +index(`;:11-:12-:12-:12-:12-:12-:12-:12-:12.:12.:12.:12.:12.:12.:12.:12.:12-', +`:12-:12-:12-:12-:12-:12-:12-:12-') @result{}-1 -index(`abc', `bc', `-4') -@result{}1 @end example +@comment Expose a bug in the gnulib replacement strstr() algorithm +@comment present from Jun 2010 to Feb 2011, including m4 1.4.15. + +@example +index(`..wi.d.', `.d.') +@result{}4 +@end example +@end ignore + @node Regexp @section Searching for regular expressions +@cindex basic regular expressions @cindex regular expressions @cindex expressions, regular -@cindex @acronym{GNU} extensions +@cindex GNU extensions Searching for regular expressions is done with the builtin @code{regexp}: -@deffn {Builtin (gnu)} regexp (@var{string}, @var{regexp}, @var{resyntax}) -@deffnx {Builtin (gnu)} regexp (@var{string}, @var{regexp}, @ - @ovar{replacement}, @ovar{resyntax}) -Searches for @var{regexp} in @var{string}. - -If @var{resyntax} is given, the particular flavor of regular expression -understood with respect to @var{regexp} can be changed from the current -default. @xref{Changeresyntax}, for details of the values that can be -given for this argument. If exactly three arguments given, then the -third argument is treated as @var{resyntax} only if it matches a known -syntax name, otherwise it is treated as @var{replacement}. +@deffn Builtin regexp (@var{string}, @var{regexp}, @ovar{replacement}) +Searches for @var{regexp} in @var{string}. The syntax for regular +expressions is the same as in GNU Emacs, which is similar to +BRE, Basic Regular Expressions in POSIX. +@ifnothtml +@xref{Regexps, , Syntax of Regular Expressions, emacs, The GNU Emacs +Manual}. +@end ifnothtml +@ifhtml +See +@uref{http://www.gnu.org/@/software/@/emacs/@/manual/@/emacs.html#Regexps, +Syntax of Regular Expressions} in the GNU Emacs Manual. +@end ifhtml +Support for ERE, Extended Regular Expressions is not +available, but will be added in GNU M4 2.0. If @var{replacement} is omitted, @code{regexp} expands to the index of the first match of @var{regexp} in @var{string}. If @var{regexp} does @@ -6976,13 +5722,13 @@ Here are some more examples on the handling of backslash: regexp(`abc', `\(b\)', `\\\10\a') @result{}\b0a regexp(`abc', `b', `\1\') -@error{}m4:stdin:2: warning: regexp: sub-expression 1 not present -@error{}m4:stdin:2: warning: regexp: trailing \ ignored in replacement +@error{}m4:stdin:2: Warning: sub-expression 1 not present +@error{}m4:stdin:2: Warning: trailing \ ignored in replacement @result{} regexp(`abc', `\(\(d\)?\)\(c\)', `\1\2\3\4\5\6') -@error{}m4:stdin:3: warning: regexp: sub-expression 4 not present -@error{}m4:stdin:3: warning: regexp: sub-expression 5 not present -@error{}m4:stdin:3: warning: regexp: sub-expression 6 not present +@error{}m4:stdin:3: Warning: sub-expression 4 not present +@error{}m4:stdin:3: Warning: sub-expression 5 not present +@error{}m4:stdin:3: Warning: sub-expression 6 not present @result{}c @end example @@ -6991,7 +5737,7 @@ contrast this with an empty @var{regexp} argument. @example regexp(`abc') -@error{}m4:stdin:1: warning: regexp: too few arguments: 1 < 2 +@error{}m4:stdin:1: Warning: too few arguments to builtin `regexp' @result{}0 regexp(`abc', `') @result{}0 @@ -6999,34 +5745,6 @@ regexp(`abc', `', `\\def') @result{}\def @end example -If @var{resyntax} is given, @var{regexp} must be given according to -the syntax chosen, though the default regular expression syntax -remains unchanged for other invocations: - -@example -regexp(`GNUs not Unix', `\w(\w+)$', `*** \& *** \1 ***', - `POSIX_EXTENDED') -@result{}*** Unix *** nix *** -regexp(`GNUs not Unix', `\w(\w+)$', `*** \& *** \1 ***') -@result{} -@end example - -Occasionally, you might want to pass an @var{resyntax} argument without -wishing to give @var{replacement}. If there are exactly three -arguments, and the last argument is a valid @var{resyntax}, it is used -as such, rather than as a replacement. - -@example -regexp(`GNUs not Unix', `\w(\w+)$', `POSIX_EXTENDED') -@result{}9 -regexp(`GNUs not Unix', `\w(\w+)$', `POSIX_EXTENDED', `POSIX_EXTENDED') -@result{}POSIX_EXTENDED -regexp(`GNUs not Unix', `\w(\w+)$', `POSIX_EXTENDED', `') -@result{} -regexp(`GNUs not Unix', `\w\(\w+\)$', `POSIX_EXTENDED', `') -@result{}POSIX_EXTENDED -@end example - @node Substr @section Extracting substrings @@ -7034,33 +5752,13 @@ regexp(`GNUs not Unix', `\w\(\w+\)$', `POSIX_EXTENDED', `') @cindex substrings, extracting Substrings are extracted with @code{substr}: -@deffn {Builtin (m4)} substr (@var{string}, @var{from}, @ovar{length}, @ - @ovar{replace}) -Performs a substring operation on @var{string}. If @var{from} is -positive, it represents the 0-based index where the substring begins. -If @var{length} is omitted, the substring ends at the end of -@var{string}; if it is positive, @var{length} is added to the starting -index to determine the ending index. - -@cindex @acronym{GNU} extensions -As a @acronym{GNU} extension, if @var{from} is negative, it is added to -the length of @var{string} to determine the starting index; if it is -empty, the start of the string is used. Likewise, if @var{length} is -negative, it is added to the length of @var{string} to determine the -ending index, and an emtpy @var{length} behaves like an omitted -@var{length}. It is not an error if either of the resulting indices lie -outside the string, but the selected substring only contains the bytes -of @var{string} that overlap the selected indices. If the end point -lies before the beginning point, the substring chosen is the empty -string located at the starting index. - -If @var{replace} is omitted, then the expansion is only the selected -substring, which may be empty. As a @acronym{GNU} extension,if -@var{replace} is provided, then the expansion is the original -@var{string} with the selected substring replaced by @var{replace}. The -expansion is empty and a warning issued if @var{from} or @var{length} -cannot be parsed, or if @var{replace} is provided but the selected -indices do not overlap with @var{string}. +@deffn Builtin substr (@var{string}, @var{from}, @ovar{length}) +Expands to the substring of @var{string}, which starts at index +@var{from}, and extends for @var{length} characters, or to the end of +@var{string}, if @var{length} is omitted. The starting index of a string +is always 0. The expansion is empty if there is an error parsing +@var{from} or @var{length}, if @var{from} is beyond the end of +@var{string}, or if @var{length} is negative. The macro @code{substr} is recognized only with parameters. @end deffn @@ -7072,160 +5770,15 @@ substr(`gnus, gnats, and armadillos', `6', `5') @result{}gnats @end example -Omitting @var{from} evokes a warning, but still produces output. On the -other hand, selecting a @var{from} or @var{length} that lies beyond -@var{string} is not a problem. +Omitting @var{from} evokes a warning, but still produces output. @example substr(`abc') -@error{}m4:stdin:1: warning: substr: too few arguments: 1 < 2 +@error{}m4:stdin:1: Warning: too few arguments to builtin `substr' @result{}abc -substr(`abc', `') +substr(`abc',) +@error{}m4:stdin:2: empty string treated as 0 in builtin `substr' @result{}abc -substr(`abc', `4') -@result{} -substr(`abc', `1', `4') -@result{}bc -@end example - -Using negative values for @var{from} or @var{length} are @acronym{GNU} -extensions, useful for accessing a fixed size tail of an -arbitrary-length string. Prior to M4 1.6, using these values would -silently result in the empty string. Some other implementations crash -on negative values, and many treat an explicitly empty @var{length} as -0, which is different from the omitted @var{length} implying the rest of -the original @var{string}. - -@example -substr(`abcde', `2', `') -@result{}cde -substr(`abcde', `-3') -@result{}cde -substr(`abcde', `', `-3') -@result{}ab -substr(`abcde', `-6') -@result{}abcde -substr(`abcde', `-6', `5') -@result{}abcd -substr(`abcde', `-7', `1') -@result{} -substr(`abcde', `1', `-2') -@result{}bc -substr(`abcde', `-4', `-1') -@result{}bcd -substr(`abcde', `4', `-3') -@result{} -substr(`abcdefghij', `-09', `08') -@result{}bcdefghi -@end example - -Another useful @acronym{GNU} extension, also added in M4 1.6, is the -ability to replace a substring within the original @var{string}. An -empty length substring at the beginning or end of @var{string} is valid, -but selecting a substring that does not overlap @var{string} causes a -warning. - -@example -substr(`abcde', `1', `3', `t') -@result{}ate -substr(`abcde', `5', `', `f') -@result{}abcdef -substr(`abcde', `-3', `-4', `f') -@result{}abfcde -substr(`abcde', `-6', `1', `f') -@result{}fabcde -substr(`abcde', `-7', `1', `f') -@error{}m4:stdin:5: warning: substr: substring out of range -@result{} -substr(`abcde', `6', `', `f') -@error{}m4:stdin:6: warning: substr: substring out of range -@result{} -@end example - -If backwards compabitility to M4 1.4.x behavior is necessary, the -following macro is sufficient to do the job (mimicking warnings about -empty @var{from} or @var{length} or an ignored fourth argument is left -as an exercise to the reader). - -@example -define(`substr', `ifelse(`$#', `0', ``$0'', - eval(`2 < $#')`$3', `1', `', - index(`$2$3', `-'), `-1', `builtin(`$0', `$1', `$2', `$3')')') -@result{} -substr(`abcde', `3') -@result{}de -substr(`abcde', `3', `') -@result{} -substr(`abcde', `-1') -@result{} -substr(`abcde', `1', `-1') -@result{} -substr(`abcde', `2', `1', `C') -@result{}c -@end example - -On the other hand, it is possible to portably emulate the @acronym{GNU} -extension of negative @var{from} and @var{length} arguments across all -@code{m4} implementations, albeit with a lot more overhead. This -example uses @code{incr} and @code{decr} to normalize @samp{-08} to -something that a later @code{eval} will treat as a decimal value, rather -than looking like an invalid octal number, while avoiding using these -macros on an empty string. The helper macro @code{_substr_normalize} is -recursive, since it is easier to fix @var{length} after @var{from} has -been normalized, with the final iteration supplying two non-negative -arguments to the original builtin, now named @code{_substr}. - -@comment options: -daq -t_substr -@example -$ @kbd{m4 -daq -t _substr} -define(`_substr', defn(`substr'))dnl -define(`substr', `ifelse(`$#', `0', ``$0'', - `_$0(`$1', _$0_normalize(len(`$1'), - ifelse(`$2', `', `0', `incr(decr(`$2'))'), - ifelse(`$3', `', `', `incr(decr(`$3'))')))')')dnl -define(`_substr_normalize', `ifelse( - eval(`$2 < 0 && $1 + $2 >= 0'), `1', - `$0(`$1', eval(`$1 + $2'), `$3')', - eval(`$2 < 0')`$3', `1', ``0', `$1'', - eval(`$2 < 0 && $3 - 0 >= 0 && $1 + $2 + $3 - 0 >= 0'), `1', - `$0(`$1', `0', eval(`$1 + $2 + $3 - 0'))', - eval(`$2 < 0 && $3 - 0 >= 0'), `1', ``0', `0'', - eval(`$2 < 0'), `1', `$0(`$1', `0', `$3')', - `$3', `', ``$2', `$1'', - eval(`$3 - 0 < 0 && $1 - $2 + $3 - 0 >= 0'), `1', - ``$2', eval(`$1 - $2 + $3')', - eval(`$3 - 0 < 0'), `1', ``$2', `0'', - ``$2', `$3'')')dnl -substr(`abcde', `2', `') -@error{}m4trace: -1- _substr(`abcde', `2', `5') -@result{}cde -substr(`abcde', `-3') -@error{}m4trace: -1- _substr(`abcde', `2', `5') -@result{}cde -substr(`abcde', `', `-3') -@error{}m4trace: -1- _substr(`abcde', `0', `2') -@result{}ab -substr(`abcde', `-6') -@error{}m4trace: -1- _substr(`abcde', `0', `5') -@result{}abcde -substr(`abcde', `-6', `5') -@error{}m4trace: -1- _substr(`abcde', `0', `4') -@result{}abcd -substr(`abcde', `-7', `1') -@error{}m4trace: -1- _substr(`abcde', `0', `0') -@result{} -substr(`abcde', `1', `-2') -@error{}m4trace: -1- _substr(`abcde', `1', `2') -@result{}bc -substr(`abcde', `-4', `-1') -@error{}m4trace: -1- _substr(`abcde', `1', `3') -@result{}bcd -substr(`abcde', `4', `-3') -@error{}m4trace: -1- _substr(`abcde', `4', `0') -@result{} -substr(`abcdefghij', `-09', `08') -@error{}m4trace: -1- _substr(`abcdefghij', `1', `8') -@result{}bcdefghi @end example @node Translit @@ -7235,7 +5788,7 @@ substr(`abcdefghij', `-09', `08') @cindex characters, translating Character translation is done with @code{translit}: -@deffn {Builtin (m4)} translit (@var{string}, @var{chars}, @ovar{replacement}) +@deffn Builtin translit (@var{string}, @var{chars}, @ovar{replacement}) Expands to @var{string}, with each character that occurs in @var{chars} translated into the character from @var{replacement} with the same index. @@ -7250,7 +5803,7 @@ the first instance is used in making the translation. Only a single translation pass is made, even if characters in @var{replacement} also appear in @var{chars}. -As a @acronym{GNU} extension, both @var{chars} and @var{replacement} can +As a GNU extension, both @var{chars} and @var{replacement} can contain character-ranges, e.g., @samp{a-z} (meaning all lowercase letters) or @samp{0-9} (meaning all digits). To include a dash @samp{-} in @var{chars} or @var{replacement}, place it first or last in the @@ -7287,35 +5840,66 @@ example shows that @samp{a} is mapped to @samp{b}, not @samp{c}; the resulting @samp{b} is not further remapped to @samp{g}; the @samp{d} and @samp{e} are swapped, and the @samp{f} is discarded. +@ignore +@comment No need to fight 8-bit characters, as it is difficult to get +@comment rendering right in both info and dvi. + +@example +translit(`«abc~', `~-»') +@result{}abc +@end example + +@comment Stress test short arguments, since they use a different code +@comment path. +@example +translit(`abcdeabcde', `a') +@result{}bcdebcde +translit(`abcdeabcde', `ab') +@result{}cdecde +translit(`abcdeabcde', `a', `f') +@result{}fbcdefbcde +translit(`abcdeabcde', `a', `f') +@result{}fbcdefbcde +translit(`abcdeabcde', `a', `fg') +@result{}fbcdefbcde +translit(`abcdeabcde', `ab', `f') +@result{}fcdefcde +translit(`abcdeabcde', `ab', `fg') +@result{}fgcdefgcde +translit(`abcdeabcde', `ab', `ba') +@result{}bacdebacde +translit(`abcdeabcde', `e', `f') +@result{}abcdfabcdf +translit(`abc', `', `cde') +@result{}abc +translit(`', `a', `bc') +@result{} +@end example +@end ignore + Omitting @var{chars} evokes a warning, but still produces output. @example translit(`abc') -@error{}m4:stdin:1: warning: translit: too few arguments: 1 < 2 +@error{}m4:stdin:1: Warning: too few arguments to builtin `translit' @result{}abc @end example @node Patsubst @section Substituting text by regular expression +@cindex basic regular expressions @cindex regular expressions @cindex expressions, regular @cindex pattern substitution @cindex substitution by regular expression -@cindex @acronym{GNU} extensions +@cindex GNU extensions Global substitution in a string is done by @code{patsubst}: -@deffn {Builtin (gnu)} patsubst (@var{string}, @var{regexp}, @ - @ovar{replacement}, @ovar{resyntax}) +@deffn Builtin patsubst (@var{string}, @var{regexp}, @ovar{replacement}) Searches @var{string} for matches of @var{regexp}, and substitutes -@var{replacement} for each match. - -If @var{resyntax} is given, the particular flavor of regular expression -understood with respect to @var{regexp} can be changed from the current -default. @xref{Changeresyntax}, for details of the values that can be -given for this argument. Unlike @var{regexp}, if exactly three -arguments given, the third argument is always treated as -@var{replacement}, even if it matches a known syntax name. +@var{replacement} for each match. The syntax for regular expressions +is the same as in GNU Emacs (@pxref{Regexp}). The parts of @var{string} that are not covered by any match of @var{regexp} are copied to the expansion. Whenever a match is found, the @@ -7339,9 +5923,6 @@ matched by @var{regexp} is deleted. The macro @code{patsubst} is recognized only with parameters. @end deffn -When used with two arguments, @code{regexp} returns the position of the -match, but @code{patsubst} deletes the match: - @example patsubst(`GNUs not Unix', `^', `OBS: ') @result{}OBS: GNUs not Unix @@ -7354,7 +5935,7 @@ patsubst(`GNUs not Unix', `\w+', `(\&)') patsubst(`GNUs not Unix', `[A-Z][a-z]+') @result{}GN not@w{ } patsubst(`GNUs not Unix', `not', `NOT\') -@error{}m4:stdin:6: warning: patsubst: trailing \ ignored in replacement +@error{}m4:stdin:6: Warning: trailing \ ignored in replacement @result{}GNUs NOT Unix @end example @@ -7412,19 +5993,6 @@ undivert(`capitalize.m4')dnl @result{}divert`'dnl @end example -If @var{resyntax} is given, @var{regexp} must be given according to -the syntax chosen, though the default regular expression syntax -remains unchanged for other invocations: - -@example -define(`epatsubst', - `builtin(`patsubst', `$1', `$2', `$3', `POSIX_EXTENDED')')dnl -epatsubst(`bar foo baz Foo', `(\w*) (foo|Foo)', `_\1_') -@result{}_bar_ _baz_ -patsubst(`bar foo baz Foo', `\(\w*\) \(foo\|Foo\)', `_\1_') -@result{}_bar_ _baz_ -@end example - While @code{regexp} replaces the whole input with the replacement as soon as there is a match, @code{patsubst} replaces each @emph{occurrence} of a match and preserves non-matching pieces: @@ -7446,7 +6014,7 @@ contrast this with an empty @var{regexp} argument. @example patsubst(`abc') -@error{}m4:stdin:1: warning: patsubst: too few arguments: 1 < 2 +@error{}m4:stdin:1: Warning: too few arguments to builtin `patsubst' @result{}abc patsubst(`abc', `') @result{}abc @@ -7459,10 +6027,10 @@ patsubst(`abc', `', `\\-') @cindex formatted output @cindex output, formatted -@cindex @acronym{GNU} extensions +@cindex GNU extensions Formatted output can be made with @code{format}: -@deffn {Builtin (gnu)} format (@var{format-string}, @dots{}) +@deffn Builtin format (@var{format-string}, @dots{}) Works much like the C function @code{printf}. The first argument @var{format-string} can contain @samp{%} specifications which are satisfied by additional arguments, and the expansion of @code{format} is @@ -7534,29 +6102,32 @@ positional arguments, the @samp{n}, @samp{p}, @samp{S}, and @samp{C} specifiers, the @samp{z}, @samp{t}, @samp{j}, @samp{L} and @samp{ll} modifiers, and any platform extensions available in the native @code{printf}. For more details on the functioning of @code{printf}, -see the C Library Manual, or the @acronym{POSIX} specification (for +see the C Library Manual, or the POSIX specification (for example, @samp{%a} is supported even on platforms that haven't yet implemented C99 hexadecimal floating point output natively). -@c FIXME - format still needs some improvements. -Warnings are issued for unrecognized specifiers, an improper number of -arguments, or difficulty parsing an argument according to the format -string (such as overflow or extra characters). It is anticipated that a -future release of @acronym{GNU} @code{m4} will support more specifiers. -Likewise, escape sequences are not yet recognized. +Unrecognized specifiers result in a warning. It is anticipated that a +future release of GNU @code{m4} will support more specifiers, +and give better warnings when various problems such as overflow are +encountered. Likewise, escape sequences are not yet recognized. @example format(`%p', `0') -@error{}m4:stdin:1: warning: format: unrecognized specifier in `%p' -@result{}p -format(`%*d', `') -@error{}m4:stdin:2: warning: format: empty string treated as 0 -@error{}m4:stdin:2: warning: format: too few arguments: 2 < 3 -@result{}0 -format(`%.1f', `2a') -@error{}m4:stdin:3: warning: format: non-numeric argument `2a' -@result{}2.0 +@error{}m4:stdin:1: Warning: unrecognized specifier in `%p' +@result{} +@end example + +@ignore +@comment Expose a crash with a bad format string fixed in 1.4.15. +@comment Unfortuntely, 8-bit bytes are hard to check for; but the +@comment exit status is enough to sniff the crash in broken versions. + +@comment xerr: ignore +@example +format(`%'format(`%c', `128')) +@result{} @end example +@end ignore @node Arithmetic @chapter Macros for doing arithmetic @@ -7570,7 +6141,6 @@ decrement operations. @menu * Incr:: Decrement and increment operators * Eval:: Evaluating integer expressions -* Mpeval:: Multiple precision arithmetic @end menu @node Incr @@ -7581,8 +6151,8 @@ decrement operations. Increment and decrement of integers are supported using the builtins @code{incr} and @code{decr}: -@deffn {Builtin (m4)} incr (@var{number}) -@deffnx {Builtin (m4)} decr (@var{number}) +@deffn Builtin incr (@var{number}) +@deffnx Builtin decr (@var{number}) Expand to the numerical value of @var{number}, incremented or decremented, respectively, by one. Except for the empty string, the expansion is empty if @var{number} could not be parsed. @@ -7597,16 +6167,13 @@ incr(`4') decr(`7') @result{}6 incr() -@error{}m4:stdin:3: warning: incr: empty string treated as 0 +@error{}m4:stdin:3: empty string treated as 0 in builtin `incr' @result{}1 decr() -@error{}m4:stdin:4: warning: decr: empty string treated as 0 +@error{}m4:stdin:4: empty string treated as 0 in builtin `decr' @result{}-1 @end example -The builtin macros @code{incr} and @code{decr} are recognized only when -given arguments. - @node Eval @section Evaluating integer expressions @@ -7615,17 +6182,14 @@ given arguments. @cindex expressions, evaluation of integer Integer expressions are evaluated with @code{eval}: -@deffn {Builtin (m4)} eval (@var{expression}, @dvar{radix, 10}, @ovar{width}) +@deffn Builtin eval (@var{expression}, @dvar{radix, 10}, @ovar{width}) Expands to the value of @var{expression}. The expansion is empty if a problem is encountered while parsing the arguments. If specified, @var{radix} and @var{width} control the format of the output. -Calculations are done with signed numbers, using at least 31-bit -precision, but as a @acronym{GNU} extension, @code{m4} will use wider -integers if available. Precision is finite, based on the platform's -notion of @code{intmax_t}, and overflow silently results in wraparound. -A warning is issued if division by zero is attempted, or if -@var{expression} could not be parsed. +Calculations are done with 32-bit signed numbers. Overflow silently +results in wraparound. A warning is issued if division by zero is +attempted, or if @var{expression} could not be parsed. Expressions can contain the following operators, listed in order of decreasing precedence. @@ -7637,12 +6201,12 @@ Parentheses Unary plus and minus, and bitwise and logical negation @item ** Exponentiation -@item * / % \ -Multiplication, division, modulo, and ratio +@item * / % +Multiplication, division, and modulo @item + - Addition and subtraction -@item << >> >>> -Shift left, shift right, unsigned shift right +@item << >> +Shift left or right @item > >= < <= Relational operators @item == != @@ -7657,10 +6221,6 @@ Bitwise or Logical and @item || Logical or -@item ?: -Conditional ternary -@item , -Sequential evaluation @end table The macro @code{eval} is recognized only with parameters. @@ -7670,19 +6230,36 @@ All binary operators, except exponentiation, are left associative. C operators that perform variable assignment, such as @samp{+=} or @samp{--}, are not implemented, since @code{eval} only operates on constants, not variables. Attempting to use them results in an error. -@comment FIXME - since XCU ERN 137 is approved, we could provide an -@comment extension that supported assignment operators. +However, since traditional implementations treated @samp{=} as an +undocumented alias for @samp{==} as opposed to an assignment operator, +this usage is supported as a special case. Be aware that a future +version of GNU M4 may support assignment semantics as an +extension when POSIX mode is not requested, and that using +@samp{=} to check equality is not portable. + +@comment status: 1 +@example +eval(`2 = 2') +@error{}m4:stdin:1: Warning: recommend ==, not =, for equality operator +@result{}1 +eval(`++0') +@error{}m4:stdin:2: invalid operator in eval: ++0 +@result{} +eval(`0 |= 1') +@error{}m4:stdin:3: invalid operator in eval: 0 |= 1 +@result{} +@end example Note that some older @code{m4} implementations use @samp{^} as an -alternate operator for the exponentiation, although @acronym{POSIX} +alternate operator for the exponentiation, although POSIX requires the C behavior of bitwise exclusive-or. The precedence of the negation operators, @samp{~} and @samp{!}, was traditionally lower than equality. The unary operators could not be used reliably more than once on the same term without intervening parentheses. The traditional precedence of the equality operators @samp{==} and @samp{!=} was identical instead of lower than the relational operators such as -@samp{<}, even through @acronym{GNU} M4 1.4.8. Starting with version -1.4.9, @acronym{GNU} M4 correctly follows @acronym{POSIX} precedence +@samp{<}, even through GNU M4 1.4.8. Starting with version +1.4.9, GNU M4 correctly follows POSIX precedence rules. M4 scripts designed to be portable between releases must be aware that parentheses may be required to enforce C precedence rules. Likewise, division by zero, even in the unused branch of a @@ -7709,39 +6286,23 @@ eval(`(1 | 1) ^ 1') @result{}0 eval(`+ + - ~ ! ~ 0') @result{}1 -eval(`++0') -@error{}m4:stdin:8: warning: eval: invalid operator: `++0' -@result{} -eval(`1 = 1') -@error{}m4:stdin:9: warning: eval: invalid operator: `1 = 1' -@result{} -eval(`0 |= 1') -@error{}m4:stdin:10: warning: eval: invalid operator: `0 |= 1' -@result{} eval(`2 || 1 / 0') @result{}1 eval(`0 || 1 / 0') -@error{}m4:stdin:12: warning: eval: divide by zero: `0 || 1 / 0' +@error{}m4:stdin:9: divide by zero in eval: 0 || 1 / 0 @result{} eval(`0 && 1 % 0') @result{}0 eval(`2 && 1 % 0') -@error{}m4:stdin:14: warning: eval: modulo by zero: `2 && 1 % 0' +@error{}m4:stdin:11: modulo by zero in eval: 2 && 1 % 0 @result{} @end example -@cindex @acronym{GNU} extensions -As a @acronym{GNU} extension, @code{eval} supports several operators -that do not appear in C@. A right-associative exponentiation operator -@samp{**} computes the value of the left argument raised to the right, -modulo the numeric precision width. If evaluated, the exponent must be -non-negative, and at least one of the arguments must be non-zero, or a -warning is issued. An unsigned shift operator @samp{>>>} allows -shifting a negative number as though it were an unsigned bit pattern, -which shifts in 0 bits rather than twos-complement sign-extension. A -ratio operator @samp{\} behaves like normal division @samp{/} on -integers, but is provided for symmetry with @code{mpeval}. -Additionally, the C operators @samp{,} and @samp{?:} are supported. +@cindex GNU extensions +As a GNU extension, the operator @samp{**} performs integral +exponentiation. The operator is right-associative, and if evaluated, +the exponent must be non-negative, and at least one of the arguments +must be non-zero, or a warning is issued. @example eval(`2 ** 3 ** 2') @@ -7754,34 +6315,16 @@ eval(`2 ** 0') @result{}1 eval(`0 ** 0') @result{} -@error{}m4:stdin:5: warning: eval: divide by zero: `0 ** 0' +@error{}m4:stdin:5: divide by zero in eval: 0 ** 0 eval(`4 ** -2') -@error{}m4:stdin:6: warning: eval: negative exponent: `4 ** -2' +@error{}m4:stdin:6: negative exponent in eval: 4 ** -2 @result{} -eval(`2 || 4 ** -2') -@result{}1 -eval(`(-1 >> 1) == -1') -@result{}1 -eval(`(-1 >>> 1) > (1 << 30)') -@result{}1 -eval(`6 \ 3') -@result{}2 -eval(`1 ? 2 : 3') -@result{}2 -eval(`0 ? 2 : 3') -@result{}3 -eval(`1 ? 2 : 1/0') -@result{}2 -eval(`0 ? 1/0 : 3') -@result{}3 -eval(`4, 5') -@result{}5 @end example Within @var{expression}, (but not @var{radix} or @var{width}), numbers without a special prefix are decimal. A simple @samp{0} prefix introduces an octal number. @samp{0x} introduces a hexadecimal number. -As @acronym{GNU} extensions, @samp{0b} introduces a binary number. +As GNU extensions, @samp{0b} introduces a binary number. @samp{0r} introduces a number expressed in any radix between 1 and 36: the prefix should be immediately followed by the decimal expression of the radix, a colon, then the digits making the number. For radix 1, @@ -7819,7 +6362,7 @@ square(square(`5')` + 1') define(`foo', `666') @result{} eval(`foo / 6') -@error{}m4:stdin:11: warning: eval: bad expression: `foo / 6' +@error{}m4:stdin:11: bad expression in eval: foo / 6 @result{} eval(foo / 6) @result{}111 @@ -7829,21 +6372,17 @@ As the last two lines show, @code{eval} does not handle macro names, even if they expand to a valid expression (or part of a valid expression). Therefore all macros must be expanded before they are passed to @code{eval}. -@comment update this if we add support for variables. Some calculations are not portable to other implementations, since they -have undefined semantics in C, but @acronym{GNU} @code{m4} has +have undefined semantics in C, but GNU @code{m4} has well-defined behavior on overflow. When shifting, an out-of-range shift -amount is implicitly brought into the range of the precision using -modulo arithmetic (for example, on 32-bit integers, this would be an -implicit bit-wise and with 0x1f). This example should work whether your -platform uses 32-bit integers, 64-bit integers, or even some other -atypical size. +amount is implicitly brought into the range of 32-bit signed integers +using an implicit bit-wise and with 0x1f). @example -define(`max_int', eval(`-1 >>> 1')) +define(`max_int', eval(`0x7fffffff')) @result{} -define(`min_int', eval(max_int` + 1')) +define(`min_int', incr(max_int)) @result{} eval(min_int` < 0') @result{}1 @@ -7851,11 +6390,13 @@ eval(max_int` > 0') @result{}1 ifelse(eval(min_int` / -1'), min_int, `overflow occurred') @result{}overflow occurred +min_int +@result{}-2147483648 eval(`0x80000000 % -1') @result{}0 eval(`-4 >> 1') @result{}-2 -eval(`-4 >> 'eval(len(eval(max_int, `2'))` + 2')) +eval(`-4 >> 33') @result{}-2 @end example @@ -7864,9 +6405,7 @@ expansion. The default radix is 10; this is also the case if @var{radix} is the empty string. A warning results if the radix is outside the range of 1 through 36, inclusive. The result of @code{eval} is always taken to be signed. No radix prefix is output, and for -radices greater than 10, the digits are lower case (although some -other implementations use upper case). The output is unquoted, and -subject to further macro expansion. The @var{width} +radices greater than 10, the digits are lower case. The @var{width} argument specifies the minimum output width, excluding any negative sign. The result is zero-padded to extend the expansion to the requested width. A warning results if the width is negative. If @@ -7891,80 +6430,14 @@ eval(`10', `', `0') eval(`10', `16') @result{}a eval(`1', `37') -@error{}m4:stdin:9: warning: eval: radix out of range: 37 +@error{}m4:stdin:9: radix 37 in builtin `eval' out of range @result{} eval(`1', , `-1') -@error{}m4:stdin:10: warning: eval: negative width: -1 +@error{}m4:stdin:10: negative width to builtin `eval' @result{} eval() -@error{}m4:stdin:11: warning: eval: empty string treated as 0 -@result{}0 -eval(` ') -@error{}m4:stdin:12: warning: eval: empty string treated as 0 +@error{}m4:stdin:11: empty string treated as 0 in builtin `eval' @result{}0 -define(`a', `hi')eval(` 10 ', `16') -@result{}hi -@end example - -@node Mpeval -@section Multiple precision arithmetic - -When @code{m4} is compiled with a multiple precision arithmetic library -(@pxref{Experiments}), a builtin @code{mpeval} is defined. - -@deffn {Builtin (mpeval)} mpeval (@var{expression}, @dvar{radix, 10}, @ - @ovar{width}) -Behaves similarly to @code{eval}, except the calculations are done with -infinite precision, and rational numbers are supported. Numbers may be -of any length. - -The macro @code{mpeval} is recognized only with parameters. -@end deffn - -For the most part, using @code{mpeval} is similar to using @code{eval}: - -@comment options: -m mpeval -@example -$ @kbd{m4 -m mpeval} -mpeval(`(1 << 70) + 2 ** 68 * 3', `16') -@result{}700000000000000000 -`0r24:'mpeval(`0r36:zYx', `24', `5') -@result{}0r24:038m9 -@end example - -The ratio operator, @samp{\}, is provided with the same precedence as -division, and rationally divides two numbers and canonicalizes the -result, whereas the division operator @samp{/} always returns the -integer quotient of the division. To convert a rational value to -integral, divide (@samp{/}) by 1. Some operators, such as @samp{%}, -@samp{<<}, @samp{>>}, @samp{~}, @samp{&}, @samp{|} and @samp{^} operate -only on integers and will truncate any rational remainder. The unsigned -shift operator, @samp{>>>}, behaves identically with regular right -shifts, @samp{>>}, since with infinite precision, it is not possible to -convert a negative number to a positive using shifts. The -exponentiation operator, @samp{**}, assumes that the exponent is -integral, but allows negative exponents. With the short-circuit logical -operators, @samp{||} and @samp{&&}, a non-zero result preserves the -value of the argument that ended evaluation, rather than collapsing to -@samp{1}. The operators @samp{?:} and @samp{,} are always available, -even in @acronym{POSIX} mode, since @code{mpeval} does not have to -conform to the @acronym{POSIX} rules for @code{eval}. - -@comment options: -m mpeval -@example -$ @kbd{m4 -m mpeval} -mpeval(`2 / 4') -@result{}0 -mpeval(`2 \ 4') -@result{}1\2 -mpeval(`2 || 3') -@result{}2 -mpeval(`1 && 3') -@result{}3 -mpeval(`-1 >> 1') -@result{}-1 -mpeval(`-1 >>> 1') -@result{}-1 @end example @node Shell commands @@ -7991,7 +6464,6 @@ exit value if this is not the case. * Esyscmd:: Reading the output of commands * Sysval:: Exit status * Mkstemp:: Making temporary files -* Mkdtemp:: Making temporary directories @end menu @node Platform macros @@ -7999,34 +6471,60 @@ exit value if this is not the case. @cindex platform macros Sometimes it is desirable for an input file to know which platform -@code{m4} is running on. @acronym{GNU} @code{m4} provides several +@code{m4} is running on. GNU @code{m4} provides several macros that are predefined to expand to the empty string; checking for their existence will confirm platform details. -@deffn {Optional builtin (gnu)} __os2__ -@deffnx {Optional builtin (traditional)} os2 -@deffnx {Optional builtin (gnu)} __unix__ -@deffnx {Optional builtin (traditional)} unix -@deffnx {Optional builtin (gnu)} __windows__ -@deffnx {Optional builtin (traditional)} windows +@deffn {Optional builtin} __gnu__ +@deffnx {Optional builtin} __os2__ +@deffnx {Optional builtin} os2 +@deffnx {Optional builtin} __unix__ +@deffnx {Optional builtin} unix +@deffnx {Optional builtin} __windows__ +@deffnx {Optional builtin} windows Each of these macros is conditionally defined as needed to describe the environment of @code{m4}. If defined, each macro expands to the empty -string. +string. For now, these macros silently ignore all arguments, but in a +future release of M4, they might warn if arguments are present. @end deffn -On UNIX systems, @acronym{GNU} @code{m4} will define @code{@w{__unix__}} -in the @samp{gnu} module, and @code{unix} in the @samp{traditional} -module. +When GNU extensions are in effect (that is, when you did not +use the @option{-G} option, @pxref{Limits control, , Invoking m4}), +GNU @code{m4} will define the macro @code{@w{__gnu__}} to +expand to the empty string. -On native Windows systems, @acronym{GNU} @code{m4} will define -@code{@w{__windows__}} in the @samp{gnu} module, and @code{windows} in -the @samp{traditional} module. +@example +$ @kbd{m4} +__gnu__ +@result{} +__gnu__(`ignored') +@result{} +Extensions are ifdef(`__gnu__', `active', `inactive') +@result{}Extensions are active +@end example -On OS/2 systems, @acronym{GNU} @code{m4} will define @code{@w{__os2__}} -in the @samp{gnu} module, and @code{os2} in the @samp{traditional} -module. +@comment options: -G +@example +$ @kbd{m4 -G} +__gnu__ +@result{}__gnu__ +__gnu__(`ignored') +@result{}__gnu__(ignored) +Extensions are ifdef(`__gnu__', `active', `inactive') +@result{}Extensions are inactive +@end example -If @acronym{GNU} M4 does not provide a platform macro for your system, +On UNIX systems, GNU @code{m4} will define @code{@w{__unix__}} +by default, or @code{unix} when the @option{-G} option is specified. + +On native Windows systems, GNU @code{m4} will define +@code{@w{__windows__}} by default, or @code{windows} when the +@option{-G} option is specified. + +On OS/2 systems, GNU @code{m4} will define @code{@w{__os2__}} +by default, or @code{os2} when the @option{-G} option is specified. + +If GNU @code{m4} does not provide a platform macro for your system, please report that as a bug. @example @@ -8047,7 +6545,7 @@ provided Any shell command can be executed, using @code{syscmd}: -@deffn {Builtin (m4)} syscmd (@var{shell-command}) +@deffn Builtin syscmd (@var{shell-command}) Executes @var{shell-command} as a shell command. The expansion of @code{syscmd} is void, @emph{not} the output from @@ -8065,13 +6563,9 @@ By default, the @var{shell-command} will be used as the argument to the supports that). If you prefer a different shell, the @command{configure} script can be given the option @option{--with-syscmd-shell=@var{location}} to set the location of an -alternative shell at @acronym{GNU} @code{m4} installation; the +alternative shell at GNU @code{m4} installation; the alternative shell must still support @option{-c}. -When the @option{--safer} option (@pxref{Operation modes, , Invoking -m4}) is in effect, @code{syscmd} results in an error, since otherwise an -input file could execute arbitrary code. - The macro @code{syscmd} is recognized only with parameters. @end deffn @@ -8089,17 +6583,30 @@ the command, as well as using the newline that appeared after the macro. The following is an example of @var{shell-command} using the same standard input as @code{m4}: -@comment The testsuite does not know how to parse pipes from the -@comment texinfo. Fortunately, there are other tests in the testsuite -@comment that test this same feature. @comment ignore @example $ @kbd{echo "m4wrap(\`syscmd(\`cat')')" | m4} @result{} @end example +@ignore +@comment If the user types the example below with stdin being an +@comment interactive terminal, then cat will hang waiting for additional +@comment input after m4 has exited. But the testsuite is using a pipe +@comment for stdin. Hence, we have two versions - the one we feed the +@comment testsuite below, and the one we display to the user above that +@comment more accurately shows what the testsuite is really doing but +@comment which the testsuite cannot parse. + +@example +m4wrap(`syscmd(`cat')') +@result{} +^D +@end example +@end ignore + It tells @code{m4} to read all of its input before executing the wrapped -text, then hands a valid (albeit emptied) pipe as standard input for the +text, then hand a valid (albeit emptied) pipe as standard input for the @code{cat} subcommand. Therefore, you should be careful when using standard input (either by specifying no files, or by passing @samp{-} as a file name on the command line, @pxref{Command line files, , Invoking @@ -8110,26 +6617,14 @@ yet processed by @code{m4}; when it is a pipe or other non-seekable file, there is no guarantee how much data will already be buffered by @code{m4} and thus unavailable to the child. -Following is an example of how potentially unsafe actions can be -suppressed. - -@comment options: --safer -@comment status: 1 -@example -$ @kbd{m4 --safer} -syscmd(`echo hi') -@error{}m4:stdin:1: syscmd: disabled by --safer -@result{} -@end example - @node Esyscmd @section Reading the output of commands -@cindex @acronym{GNU} extensions +@cindex GNU extensions If you want @code{m4} to read the output of a shell command, use @code{esyscmd}: -@deffn {Builtin (gnu)} esyscmd (@var{shell-command}) +@deffn Builtin esyscmd (@var{shell-command}) Expands to the standard output of the shell command @var{shell-command}. @@ -8145,13 +6640,9 @@ By default, the @var{shell-command} will be used as the argument to the supports that). If you prefer a different shell, the @command{configure} script can be given the option @option{--with-syscmd-shell=@var{location}} to set the location of an -alternative shell at @acronym{GNU} @code{m4} installation; the +alternative shell at GNU @code{m4} installation; the alternative shell must still support @option{-c}. -When the @option{--safer} option (@pxref{Operation modes, , Invoking -m4}) is in effect, @code{esyscmd} results in an error, since otherwise -an input file could execute arbitrary code. - The macro @code{esyscmd} is recognized only with parameters. @end deffn @@ -8168,16 +6659,6 @@ the command, as well as using the newline that appeared after the macro. Just as with @code{syscmd}, care must be exercised when sharing standard input between @code{m4} and the child process of @code{esyscmd}. -Likewise, potentially unsafe actions can be suppressed. - -@comment options: --safer -@comment status: 1 -@example -$ @kbd{m4 --safer} -esyscmd(`echo hi') -@error{}m4:stdin:1: esyscmd: disabled by --safer -@result{} -@end example @node Sysval @section Exit status @@ -8189,7 +6670,7 @@ esyscmd(`echo hi') @cindex status of shell commands To see whether a shell command succeeded, use @code{sysval}: -@deffn {Builtin (m4)} sysval +@deffn Builtin sysval Expands to the exit status of the last shell command run with @code{syscmd} or @code{esyscmd}. Expands to 0 if no command has been run yet. @@ -8265,23 +6746,6 @@ sysval @result{}2304 @end example -When the @option{--safer} option (@pxref{Operation modes, , Invoking -m4}) is in effect, @code{sysval} will always remain at its default value -of zero. - -@comment options: --safer -@comment status: 1 -@example -$ @kbd{m4 --safer} -sysval -@result{}0 -syscmd(`false') -@error{}m4:stdin:2: syscmd: disabled by --safer -@result{} -sysval -@result{}0 -@end example - @node Mkstemp @section Making temporary files @@ -8291,8 +6755,8 @@ Commands specified to @code{syscmd} or @code{esyscmd} might need a temporary file, for output or for some other purpose. There is a builtin macro, @code{mkstemp}, for making a temporary file: -@deffn {Builtin (m4)} mkstemp (@var{template}) -@deffnx {Builtin (m4)} maketemp (@var{template}) +@deffn Builtin mkstemp (@var{template}) +@deffnx Builtin maketemp (@var{template}) Expands to the quoted name of a new, empty file, made from the string @var{template}, which should end with the string @samp{XXXXXX}. The six @samp{X} characters are then replaced with random characters matching @@ -8303,7 +6767,7 @@ created file will have access permissions as if by @kbd{chmod =rw,go=}, meaning that the current umask of the @code{m4} process is taken into account, and at most only the current user can read and write the file. -The traditional behavior, standardized by @acronym{POSIX}, is that +The traditional behavior, standardized by POSIX, is that @code{maketemp} merely replaces the trailing @samp{X} with the process id, without creating a file or quoting the expansion, and without ensuring that the resulting @@ -8312,18 +6776,13 @@ string is a unique file name. In part, this means that using the same expansion. This behavior is a security hole, as it is very easy for another process to guess the name that will be generated, and thus interfere with a subsequent use of @code{syscmd} trying to manipulate -that file name. Hence, @acronym{POSIX} has recommended that all new +that file name. Hence, POSIX has recommended that all new implementations of @code{m4} provide the secure @code{mkstemp} builtin, and that users of @code{m4} check for its existence. The expansion is void and an error issued if a temporary file could not be created. -When the @option{--safer} option (@pxref{Operation modes, Invoking m4}) -is in effect, @code{mkstemp} and @acronym{GNU}-mode @code{maketemp} -result in an error, since otherwise an input file could perform a mild -denial-of-service attack by filling up a disk with multiple empty files. - The macros @code{mkstemp} and @code{maketemp} are recognized only with parameters. @end deffn @@ -8338,7 +6797,6 @@ $ @kbd{m4} define(`tmp', `oops') @result{} maketemp(`/tmp/fooXXXXXX') -@error{}m4:stdin:1: warning: maketemp: recommend using mkstemp instead @result{}/tmp/fooa07346 ifdef(`mkstemp', `define(`maketemp', defn(`mkstemp'))', `define(`mkstemp', defn(`maketemp'))dnl @@ -8349,26 +6807,13 @@ mkstemp(`doc') @result{}docQv83Uw @end example -@comment options: --safer -@comment status: 1 -@example -$ @kbd{m4 --safer} -maketemp(`/tmp/fooXXXXXX') -@error{}m4:stdin:1: warning: maketemp: recommend using mkstemp instead -@error{}m4:stdin:1: maketemp: disabled by --safer -@result{} -mkstemp(`/tmp/fooXXXXXX') -@error{}m4:stdin:2: mkstemp: disabled by --safer -@result{} -@end example - -@cindex @acronym{GNU} extensions +@cindex GNU extensions Unless you use the @option{--traditional} command line option (or -@option{-G}, @pxref{Limits control, , Invoking m4}), the @acronym{GNU} +@option{-G}, @pxref{Limits control, , Invoking m4}), the GNU version of @code{maketemp} is secure. This means that using the same template to multiple calls will generate multiple files. However, we recommend that you use the new @code{mkstemp} macro, introduced in -@acronym{GNU} M4 1.4.8, which is secure even in traditional mode. Also, +GNU M4 1.4.8, which is secure even in traditional mode. Also, as of M4 1.4.11, the secure implementation quotes the resulting file name, so that you are guaranteed to know what file was created even if the random file name happens to match an existing macro. Notice that @@ -8382,12 +6827,10 @@ define(`foo', `errprint(`oops')') syscmd(`rm -f foo-??????')sysval @result{}0 define(`file1', maketemp(`foo-XXXXXX'))dnl -@error{}m4:stdin:3: warning: maketemp: recommend using mkstemp instead -ifelse(esyscmd(`echo \` foo-?????? \''), `foo-??????', +ifelse(esyscmd(`echo \` foo-?????? \''), ` foo-?????? ', `no file', `created') @result{}created define(`file2', maketemp(`foo-XX'))dnl -@error{}m4:stdin:6: warning: maketemp: recommend using mkstemp instead define(`file3', mkstemp(`foo-XXXXXX'))dnl ifelse(len(defn(`file1')), len(defn(`file2')), `same length', `different') @@ -8404,105 +6847,40 @@ sysval @result{}0 @end example +@ignore +@c Not worth documenting, but make sure we don't leave trailing NUL in +@c the expansion. + +@example +syscmd(`rm -rf foodir')sysval +@result{}0 +syscmd(`mkdir foodir')sysval +@result{}0 +len(mkstemp(`foodir/fooXXXXX')) +@result{}16 +syscmd(`rm -r foodir')sysval +@result{}0 +@end example + +@c Likewise, and ensure that traditional mode leaves the result unquoted +@c without creating a file. + @comment options: -G @example -$ @kbd{m4 -G} syscmd(`rm -f foo-*')sysval @result{}0 -define(`file1', maketemp(`foo-XXXXXX'))dnl -@error{}m4:stdin:2: warning: maketemp: recommend using mkstemp instead -define(`file2', maketemp(`foo-XXXXXX'))dnl -@error{}m4:stdin:3: warning: maketemp: recommend using mkstemp instead -ifelse(file1, file2, `same', `different file') -@result{}same len(maketemp(`foo-XXXXX')) -@error{}m4:stdin:5: warning: maketemp: recommend using mkstemp instead +@error{}m4:stdin:2: recommend using mkstemp instead @result{}9 define(`abc', `def') @result{} maketemp(`foo-abc') @result{}foo-def -@error{}m4:stdin:7: warning: maketemp: recommend using mkstemp instead -syscmd(`test -f foo-*')sysval +@error{}m4:stdin:4: recommend using mkstemp instead +syscmd(`test -f foo-*')ifelse(sysval, `0', `0', `1') @result{}1 @end example - -@node Mkdtemp -@section Making temporary directories - -@cindex temporary directory -@cindex directories, temporary -@cindex @acronym{GNU} extensions -Commands specified to @code{syscmd} or @code{esyscmd} might need a -temporary directory, for holding multiple temporary files; such a -directory can be created with @code{mkdtemp}: - -@deffn {Builtin (gnu)} mkdtemp (@var{template}) -Expands to the quoted name of a new, empty directory, made from the string -@var{template}, which should end with the string @samp{XXXXXX}. The six -@samp{X} characters are then replaced with random characters matching -the regular expression @samp{[a-zA-Z0-9._-]}, in order to make the name -unique. If fewer than six @samp{X} characters are found at the end of -@code{template}, the result will be longer than the template. The -created directory will have access permissions as if by @kbd{chmod -=rwx,go=}, meaning that the current umask of the @code{m4} process is -taken into account, and at most only the current user can read, write, -and search the directory. - -The expansion is void and an error issued if a temporary directory could -not be created. - -When the @option{--safer} option (@pxref{Operation modes, Invoking m4}) -is in effect, @code{mkdtemp} results in an error, since otherwise an -input file could perform a mild denial-of-service attack by filling up a -disk with multiple directories. - -The macro @code{mkdtemp} is recognized only with parameters. -This macro was added in M4 2.0. -@end deffn - -If you try this next example, you will most likely get different output -for the directory names, since the replacement characters are randomly -chosen: - -@comment ignore -@example -$ @kbd{m4} -define(`tmp', `oops') -@result{} -mkdtemp(`/tmp/fooXXXXXX') -@result{}/tmp/foo2h89Vo -mkdtemp(`dir) -@result{}dirrg079A -@end example - -@comment options: --safer -@comment status: 1 -@example -$ @kbd{m4 --safer} -mkdtemp(`/tmp/fooXXXXXX') -@error{}m4:stdin:1: mkdtemp: disabled by --safer -@result{} -@end example - -Multiple calls with the same template will generate multiple -directories. - -@example -$ @kbd{m4} -syscmd(`echo foo??????')dnl -@result{}foo?????? -define(`dir1', mkdtemp(`fooXXXXXX'))dnl -ifelse(esyscmd(`echo foo??????'), `foo??????', `no dir', `created') -@result{}created -define(`dir2', mkdtemp(`fooXXXXXX'))dnl -ifelse(dir1, dir2, `same', `different directories') -@result{}different directories -syscmd(`rmdir 'dir1 dir2) -@result{} -sysval -@result{}0 -@end example +@end ignore @node Miscellaneous @chapter Miscellaneous builtin macros @@ -8514,7 +6892,6 @@ any of the previous chapters. * Errprint:: Printing error messages * Location:: Printing current location * M4exit:: Exiting from @code{m4} -* Syncoutput:: Turning on and off sync lines @end menu @node Errprint @@ -8526,7 +6903,7 @@ any of the previous chapters. @cindex standard error, output to You can print error messages using @code{errprint}: -@deffn {Builtin (m4)} errprint (@var{message}, @dots{}) +@deffn Builtin errprint (@var{message}, @dots{}) Prints @var{message} and the rest of the arguments to standard error, separated by spaces. Standard error is used, regardless of the @option{--debugfile} option (@pxref{Debugging options, , Invoking m4}). @@ -8549,11 +6926,11 @@ errprint(`1')errprint(`2',`3 A trailing newline is @emph{not} printed automatically, so it should be supplied as part of the argument, as in the example. Unfortunately, the exact output of @code{errprint} is not very portable to other @code{m4} -implementations: @acronym{POSIX} requires that all arguments be printed, +implementations: POSIX requires that all arguments be printed, but some implementations of @code{m4} only print the first. -Furthermore, some @acronym{BSD} implementations always append a newline +Furthermore, some BSD implementations always append a newline for each @code{errprint} call, regardless of whether the last argument -already had one, and @acronym{POSIX} is silent on whether this is +already had one, and POSIX is silent on whether this is acceptable. @node Location @@ -8564,9 +6941,9 @@ acceptable. To make it possible to specify the location of an error, three utility builtins exist: -@deffn {Builtin (gnu)} __file__ -@deffnx {Builtin (gnu)} __line__ -@deffnx {Builtin (gnu)} __program__ +@deffn Builtin __file__ +@deffnx Builtin __line__ +@deffnx Builtin __program__ Expand to the quoted name of the current input file, the current input line number in that file, and the quoted name of the current invocation of @code{m4}. @@ -8581,10 +6958,9 @@ errprint(__program__:__file__:__line__: `input error Line numbers start at 1 for each file. If the file was found due to the @option{-I} option or @env{M4PATH} environment variable, that is -reflected in the file name. Synclines, via @code{syncoutput} -(@pxref{Syncoutput}) or the command line option @option{--synclines} -(or @option{-s}, @pxref{Preprocessor features, , Invoking m4}), and the -@samp{f} and @samp{l} flags of @code{debugmode} (@pxref{Debugmode}), +reflected in the file name. The syncline option (@option{-s}, +@pxref{Preprocessor features, , Invoking m4}), and the +@samp{f} and @samp{l} flags of @code{debugmode} (@pxref{Debug Levels}), also use this notion of current file and line. Redefining the three location macros has no effect on syncline, debug, warning, or error message output. @@ -8609,7 +6985,7 @@ include(`incl.m4') The location of macros invoked during the rescanning of macro expansion text corresponds to the location in the file where the expansion was triggered, regardless of how many newline characters the expansion text -contains. As of @acronym{GNU} M4 1.4.8, the location of text wrapped +contains. As of GNU M4 1.4.8, the location of text wrapped with @code{m4wrap} (@pxref{M4wrap}) is the point at which the @code{m4wrap} was invoked. Previous versions, however, behaved as though wrapped text came from line 0 of the file ``''. @@ -8640,9 +7016,9 @@ m4wrap(`__line__ ') @result{} ^D +@result{}12 @result{}6 @result{}6 -@result{}12 @end example The @code{@w{__program__}} macro behaves like @samp{$0} in shell @@ -8654,7 +7030,7 @@ same formatting that @code{m4} produces internally. It can also be used within @code{syscmd} (@pxref{Syscmd}) to pick the same version of @code{m4} that is currently running, rather than whatever version of @code{m4} happens to be first in @env{PATH}. It was first introduced in -@acronym{GNU} M4 1.4.6. +GNU M4 1.4.6. @node M4exit @section Exiting from @code{m4} @@ -8664,7 +7040,7 @@ within @code{syscmd} (@pxref{Syscmd}) to pick the same version of If you need to exit from @code{m4} before the entire input has been read, you can use @code{m4exit}: -@deffn {Builtin (m4)} m4exit (@ovar{code}) +@deffn Builtin m4exit (@dvar{code, 0}) Causes @code{m4} to exit, with exit status @var{code}. If @var{code} is left out, the exit status is zero. If @var{code} cannot be parsed, or is outside the range of 0 to 255, the exit status is one. No further @@ -8715,101 +7091,6 @@ next unread character. If it is a pipe or other non-seekable file, then there are no guarantees how much data @code{m4} might have read into buffers, and thus discarded. -@node Syncoutput -@section Turning on and off sync lines - -@cindex toggling synchronization lines -@cindex synchronization lines -@cindex location, input -@cindex input location -It is possible to adjust whether synclines are printed to output: - -@deffn {Builtin (gnu)} syncoutput (@var{truth}) -If @var{truth} matches the extended regular expression -@samp{^[1yY]|^([oO][nN])}, it causes @code{m4} to emit sync lines of the -form: @samp{#line <number> ["<file>"]}. - -If @var{truth} is empty, or matches the extended regular expression -@samp{^[0nN]|^([oO][fF])}, it causes @code{m4} to turn sync lines off. - -All other arguments are ignored and issue a warning. - -The macro @code{syncoutput} is recognized only with parameters. -This macro was added in M4 2.0. -@end deffn - -@example -define(`twoline', `1 -2') -@result{} -changecom(`/*', `*/') -@result{} -define(`comment', `/*1 -2*/') -@result{} -twoline -@result{}1 -@result{}2 -dnl no line -syncoutput(`on') -@result{}#line 8 "stdin" -@result{} -twoline -@result{}1 -@result{}#line 9 -@result{}2 -dnl no line -hello -@result{}#line 11 -@result{}hello -comment -@result{}/*1 -@result{}2*/ -one comment `two -three' -@result{}#line 13 -@result{}one /*1 -@result{}2*/ two -@result{}three -goodbye -@result{}#line 15 -@result{}goodbye -syncoutput(`off') -@result{} -twoline -@result{}1 -@result{}2 -syncoutput(`blah') -@error{}m4:stdin:18: warning: syncoutput: unknown directive `blah' -@result{} -@end example - -Notice that a syncline is output any time a single source line expands -to multiple output lines, or any time multiple source lines expand to a -single output line. When there is a one-for-one correspondence, no -additional synclines are needed. - -Synchronization lines can be used to track where input comes from; an -optional file designation is printed when the syncline algorithm -detects that consecutive output lines come from different files. You -can also use the @option{--synclines} command-line option (or -@option{-s}, @pxref{Preprocessor features, , Invoking m4}) to start -with synchronization on. This example reuses the file @file{incl.m4} -mentioned earlier (@pxref{Include}): - -@comment examples -@comment options: -s -@example -$ @kbd{m4 --synclines -I examples} -include(`incl.m4') -@result{}#line 1 "examples/incl.m4" -@result{}Include file start -@result{}foo -@result{}Include file end -@result{}#line 1 "stdin" -@result{} -@end example - @node Frozen files @chapter Fast loading of frozen state @@ -8820,13 +7101,12 @@ which files are listed on each @code{m4} invocation prior to the user's input file, or else each input file uses @code{include}. Reading the common base of a big application, over and over again, may -be time consuming. @acronym{GNU} @code{m4} offers some machinery to +be time consuming. GNU @code{m4} offers some machinery to speed up the start of an application using lengthy common bases. @menu * Using frozen files:: Using frozen files -* Frozen file format 1:: Frozen file format 1 -* Frozen file format 2:: Frozen file format 2 +* Frozen file format:: Frozen file format @end menu @node Using frozen files @@ -8837,7 +7117,7 @@ speed up the start of an application using lengthy common bases. @cindex initialization, frozen state @cindex dumping into frozen file @cindex reloading a frozen file -@cindex @acronym{GNU} extensions +@cindex GNU extensions Suppose a user has a library of @code{m4} initializations in @file{base.m4}, which is then used with multiple input files: @@ -8870,7 +7150,7 @@ $ @kbd{m4 -R base.m4f input3.m4} with the varying input. The first call, containing the @option{-F} option, only reads and executes file @file{base.m4}, defining various application macros and computing other initializations. -Once the input file @file{base.m4} has been completely processed, @acronym{GNU} +Once the input file @file{base.m4} has been completely processed, GNU @code{m4} produces in @file{base.m4f} a @dfn{frozen} file, that is, a file which contains a kind of snapshot of the @code{m4} internal state. @@ -8905,14 +7185,54 @@ $ @kbd{m4 -R file2.m4f -F file3.m4f file3.m4} $ @kbd{m4 -R file3.m4f file4.m4} @end example -Some care is necessary because the frozen file does not save all state -information. Stacks of macro definitions via @code{pushdef} are -accurately stored, along with all renamed or undefined builtins, as are -the current syntax rules such as from @code{changequote}. However, the -value of @code{sysval} and text saved in @code{m4wrap} are not currently -preserved. Also, changing command line options between runs may cause -unexpected behavior. A future release of @acronym{GNU} M4 may improve -on the quality of frozen files. +Some care is necessary because not every effort has been made for +this to work in all cases. In particular, the trace attribute of +macros is not handled, nor the current setting of @code{changeword}. +Currently, @code{m4wrap} and @code{sysval} also have problems. +Also, interactions for some options of @code{m4}, being used in one call +and not in the next, have not been fully analyzed yet. On the other +end, you may be confident that stacks of @code{pushdef} definitions +are handled correctly, as well as undefined or renamed builtins, and +changed strings for quotes or comments. And future releases of +GNU M4 will improve on the utility of frozen files. + +@ignore +@c This example is not worth putting in the manual, but caused core +@c dumps in all versions prior to 1.4.11. + +@comment options: -F /dev/null +@example +traceon(`undefined')dnl +@end example + +@c Make sure freezing is successful. + +@example +ifdef(`__unix__', , + `errprint(` skipping: syscmd does not have unix semantics +')m4exit(`77')')dnl +changequote(`[', `]')dnl +syscmd([echo 'changequote([,])pushdef([divnum],[hi])dnl' \ + | ']__program__[' -F in.m4f \ + && echo 'divnum popdef([divnum])divnum' \ + | ']__program__[' -R in.m4f \ + && rm in.m4f])status sysval +@result{}hi 0 +@result{}status 0 +@end example + +@c Detect inability to freeze. +@c Some systems harden /, and fail with EACCES rather than ENOENT. + +@comment options: -F /none/such +@comment xerr: ignore +@comment status: 1 +@example +$ @kbd{m4 -F /none/such} +^D +@error{}m4: cannot open `/none/such': No such file or directory +@end example +@end ignore When an @code{m4} run is to be frozen, the automatic undiversion which takes place at end of execution is inhibited. Instead, all @@ -8928,66 +7248,56 @@ contains directives that an older @code{m4} cannot parse, attempting to load the frozen file with option @option{-R} will cause @code{m4} to exit with status 63 to indicate version mismatch. -@node Frozen file format 1 -@section Frozen file format 1 +@node Frozen file format +@section Frozen file format -@cindex frozen file format 1 -@cindex file format, frozen file version 1 +@cindex frozen file format +@cindex file format, frozen file Frozen files are sharable across architectures. It is safe to write a frozen file on one machine and read it on another, given that the -second machine uses the same or newer version of @acronym{GNU} @code{m4}. +second machine uses the same or newer version of GNU @code{m4}. It is conventional, but not required, to give a frozen file the suffix of @code{.m4f}. -Older versions of @acronym{GNU} @code{m4} create frozen files with -syntax version 1. These files can be read by the current version, but -are no longer produced. Version 1 files are mostly text files, although -any macros or diversions that contained nonprintable characters or long -lines cause the resulting frozen file to do likewise, since there are no -escape sequences. The file can be edited to change the state that -@code{m4} will start with. It is composed of several directives, each -starting with a single letter and ending with a newline (@key{NL}). -Wherever a directive is expected, the character @samp{#} can be used -instead to introduce a comment line; empty lines are also ignored if -they are not part of an embedded string. - -In the following descriptions, each @var{len} refers to the length of a -corresponding subsequent @var{str}. Numbers are always expressed in -decimal, and an omitted number defaults to 0. The valid directives in -version 1 are: +These are simple (editable) text files, made up of directives, +each starting with a capital letter and ending with a newline +(@key{NL}). Wherever a directive is expected, the character +@samp{#} introduces a comment line; empty lines are also ignored if they +are not part of an embedded string. +In the following descriptions, each @var{len} refers to the length of +the corresponding strings @var{str} in the next line of input. Numbers +are always expressed in decimal. There are no escape characters. The +directives are: @table @code -@item V @var{number} @key{NL} -Confirms the format of the file. Version 1 is recognized when -@var{number} is 1. This directive must be the first non-comment in the -file, and may not appear more than once. - @item C @var{len1} , @var{len2} @key{NL} @var{str1} @var{str2} @key{NL} Uses @var{str1} and @var{str2} as the begin-comment and end-comment strings. If omitted, then @samp{#} and @key{NL} are the comment delimiters. @item D @var{number}, @var{len} @key{NL} @var{str} @key{NL} -Selects diversion @var{number}, making it current, then copy @var{str} -in the current diversion. @var{number} may be a negative number for a -diversion that discards text. To merely specify an active selection, -use this command with an empty @var{str}. With 0 as the diversion -@var{number}, @var{str} will be issued on standard output at reload -time. @acronym{GNU} @code{m4} will not produce the @samp{D} directive -with non-zero length for diversion 0, but this can be done with manual -edits. This directive may appear more than once for the same diversion, -in which case the diversion is the concatenation of the various uses. -If omitted, then diversion 0 is current. +Selects diversion @var{number}, making it current, then copy +@var{str} in the current diversion. @var{number} may be a negative +number for a non-existing diversion. To merely specify an active +selection, use this command with an empty @var{str}. With 0 as the +diversion @var{number}, @var{str} will be issued on standard output +at reload time. GNU @code{m4} will not produce the @samp{D} +directive with non-zero length for diversion 0, but this can be done +with manual edits. This directive may +appear more than once for the same diversion, in which case the +diversion is the concatenation of the various uses. If omitted, then +diversion 0 is current. @item F @var{len1} , @var{len2} @key{NL} @var{str1} @var{str2} @key{NL} -Defines, through @code{pushdef}, a definition for @var{str1} expanding -to the function whose builtin name is @var{str2}. If the builtin does -not exist (for example, if the frozen file was produced by a copy of -@code{m4} compiled with the now-abandoned @code{changeword} support), -the reload is silent, but any subsequent use of the definition of -@var{str1} will result in a warning. This directive may appear more -than once for the same name, and its order, along with @samp{T}, is -important. If omitted, you will have no access to any builtins. +Defines, through @code{pushdef}, a definition for @var{str1} +expanding to the function whose builtin name is @var{str2}. If the +builtin does not exist (for example, if the frozen file was produced by +a copy of @code{m4} compiled with changeword support, but the version +of @code{m4} reloading was compiled without it), the reload is silent, +but any subsequent use of the definition of @var{str1} will result in +a warning. This directive may appear more than once for the same name, +and its order, along with @samp{T}, is important. If omitted, you will +have no access to any builtins. @item Q @var{len1} , @var{len2} @key{NL} @var{str1} @var{str2} @key{NL} Uses @var{str1} and @var{str2} as the begin-quote and end-quote @@ -8999,115 +7309,12 @@ Defines, though @code{pushdef}, a definition for @var{str1} expanding to the text given by @var{str2}. This directive may appear more than once for the same name, and its order, along with @samp{F}, is important. -@end table - -When loading format 1, the syntax categories @samp{@{} and @samp{@}} are -disabled (reverting braces to be treated like plain characters). This -is because frozen files created with M4 1.4.x did not understand -@samp{$@{@dots{}@}} extended argument notation, and a frozen macro that -contained this character sequence should not behave differently just -because a newer version of M4 reloaded the file. - -@node Frozen file format 2 -@section Frozen file format 2 - -@cindex frozen file format 2 -@cindex file format, frozen file version 2 -The syntax of version 1 has some drawbacks; if any macro or diversion -contained non-printable characters or long lines, the resulting frozen -file would not qualify as a text file, making it harder to edit with -some vendor tools. The concatenation of multiple strings on a single -line, such as for the @samp{T} directive, makes distinguishing the two -strings a bit more difficult. Finally, the format lacks support for -several items of @code{m4} state, such that a reloaded file did not -always behave the same as the original file. - -These shortcomings have been addressed in version 2 of the frozen file -syntax. New directives have been added, and existing directives have -additional, and sometimes optional, parameters. All @var{str} instances -in the grammar are now followed by @key{NL}, which makes the split -between consecutive strings easier to recognize. Strings may now -contain escape sequences modeled after C, such as @samp{\n} for newline -or @samp{\0} for @sc{nul}, so that the frozen file can be pure -@sc{ascii} (although when hand-editing a frozen file, it is still -acceptable to use the original byte rather than an escape sequence for -all bytes except @samp{\}). Also in the context of a @var{str}, the -escape sequence @samp{\@key{NL}} is discarded, allowing a user to split -lines that are too long for some platform tools. -@table @code @item V @var{number} @key{NL} Confirms the format of the file. @code{m4} @value{VERSION} only creates -frozen files where @var{number} is 2. This directive must be the first -non-comment in the file, and may not appear more than once. - -@item C @var{len1} , @var{len2} @key{NL} @var{str1} @key{NL} @var{str2} @key{NL} -Uses @var{str1} and @var{str2} as the begin-comment and -end-comment strings. If omitted, then @samp{#} and @key{NL} are the -comment delimiters. - -@item d @var{len} @key{NL} @var{str} @key{NL} -Sets the debug flags, using @var{str} as the argument to -@code{debugmode}. If omitted, then the debug flags start in their -default disabled state. - -@item D @var{number} , @var{len} @key{NL} @var{str} @key{NL} -Selects diversion @var{number}, making it current, then copy @var{str} -in the current diversion. @var{number} may be a negative number for a -diversion that discards text. To merely specify an active selection, -use this command with an empty @var{string}. With 0 as the diversion -@var{number}, @var{str} will be issued on standard output at reload -time. @acronym{GNU} @code{m4} will not produce the @samp{D} directive -with non-zero length for diversion 0, but this can be done with manual -edits. This directive may appear more than once for the same diversion, -in which case the diversion is the concatenation of the various uses. -If omitted, then diversion 0 is current. - -@comment FIXME - the first usage, with only one string, is not supported -@comment in the current code -@c @item F @var{len1} @key{NL} @var{str1} @key{NL} -@item F @var{len1} , @var{len2} @key{NL} @var{str1} @key{NL} @var{str2} @key{NL} -@itemx F @var{len1} , @var{len2} , @var{len3} @key{NL} @var{str1} @key{NL} @var{str2} @key{NL} @var{str3} @key{NL} -Defines, through @code{pushdef}, a definition for @var{str1} expanding -to the function whose builtin name is given by @var{str2} (defaulting to -@var{str1} if not present). With two arguments, the builtin name is -searched for among the intrinsic builtin functions only; with three -arguments, the builtin name is searched for amongst the builtin -functions defined by the module named by @var{str3}. - -@item M @var{len} @key{NL} @var{str} @key{NL} -Names a module which will be searched for according to the module search -path and loaded. Modules loaded from a frozen file don't add their -builtin entries to the symbol table. Modules must be loaded prior to -specifying module-specific builtins via the three-argument @code{F} or -@code{T}. - -@item Q @var{len1} , @var{len2} @key{NL} @var{str1} @key{NL} @var{str2} @key{NL} -Uses @var{str1} and @var{str2} as the begin-quote and end-quote strings. -If omitted, then @samp{`} and @samp{'} are the quote delimiters. - -@item R @var{len} @key{NL} @var{str} @key{NL} -Sets the default regexp syntax, where @var{str} encodes one of the -regular expression syntaxes supported by @acronym{GNU} M4. -@xref{Changeresyntax}, for more details. - -@item S @var{syntax-code} @var{len} @key{NL} @var{str} @key{NL} -Defines, through @code{changesyntax}, a syntax category for each of the -characters in @var{str}. The @var{syntax-code} must be one of the -characters described in @ref{Changesyntax}. - -@item t @var{len} @key{NL} @var{str} @key{NL} -Enables tracing for any macro named @var{str}, similar to using the -@code{traceon} builtin. This option may occur more than once for -multiple macros; if omitted, no macro starts out as traced. - -@item T @var{len1} , @var{len2} @key{NL} @var{str1} @key{NL} @var{str2} @key{NL} -@itemx T @var{len1} , @var{len2} , @var{len3} @key{NL} @var{str1} @key{NL} @var{str2} @key{NL} @var{str3} @key{NL} -Defines, though @code{pushdef}, a definition for @var{str1} expanding to -the text given by @var{str2}. This directive may appear more than once -for the same name, and its order, along with @samp{F}, is important. If -present, the optional third argument associates the macro with a module -named by @var{str3}. +and understands frozen files where @var{number} is 1. This directive +must be the first non-comment in the file, and may not appear more than +once. @end table @node Compatibility @@ -9116,59 +7323,79 @@ named by @var{str3}. @cindex compatibility This chapter describes the many of the differences between this implementation of @code{m4}, and of other implementations found under -UNIX, such as System V Release 3, Solaris, and @acronym{BSD} flavors. +UNIX, such as System V Release 3, Solaris, and BSD flavors. In particular, it lists the known differences and extensions to -@acronym{POSIX}. However, the list is not necessarily comprehensive. +POSIX. However, the list is not necessarily comprehensive. -At the time of this writing, @acronym{POSIX} 2001 (also known as IEEE +At the time of this writing, POSIX 2001 (also known as IEEE Std 1003.1-2001) is the latest standard, although a new version of -@acronym{POSIX} is under development and includes several proposals for +POSIX is under development and includes several proposals for modifying what @code{m4} is required to do. The requirements for -@code{m4} are shared between @acronym{SUSv3} and @acronym{POSIX}, and +@code{m4} are shared between SUSv3 and POSIX, and can be viewed at @uref{http://www.opengroup.org/onlinepubs/@/000095399/@/utilities/@/m4.html}. @menu -* Extensions:: Extensions in @acronym{GNU} M4 -* Incompatibilities:: Other incompatibilities -* Experiments:: Experimental features in @acronym{GNU} M4 +* Extensions:: Extensions in GNU M4 +* Incompatibilities:: Facilities in System V m4 not in GNU M4 +* Other Incompatibilities:: Other incompatibilities @end menu @node Extensions -@section Extensions in @acronym{GNU} M4 +@section Extensions in GNU M4 -@cindex @acronym{GNU} extensions -@cindex @acronym{POSIX} -@cindex @env{POSIXLY_CORRECT} +@cindex GNU extensions +@cindex POSIX This version of @code{m4} contains a few facilities that do not exist in System V @code{m4}. These extra facilities are all suppressed by -using the @option{-G} command line option, unless overridden by other -command line options. -Most of these extensions are compatible with -@uref{http://www.unix.org/single_unix_specification/, -@acronym{POSIX}}; the few exceptions are suppressed if the -@env{POSIXLY_CORRECT} environment variable is set. +using the @option{-G} command line option (@pxref{Limits control, , +Invoking m4}), unless overridden by other command line options. @itemize @bullet @item In the @code{$@var{n}} notation for macro arguments, @var{n} can contain several digits, while the System V @code{m4} only accepts one digit. -This allows macros in @acronym{GNU} @code{m4} to take any number of +This allows macros in GNU @code{m4} to take any number of arguments, and not only nine (@pxref{Arguments}). -@acronym{POSIX} does not allow this extension, so it is disabled if -@env{POSIXLY_CORRECT} is set. -@c FIXME - update this bullet when ${11} is implemented. + +This means that @code{define(`foo', `$11')} is ambiguous between +implementations. To portably choose between grabbing the first +parameter and appending 1 to the expansion, or grabbing the eleventh +parameter, you can do the following: + +@example +define(`a1', `A1') +@result{} +dnl First argument, concatenated with 1 +define(`_1', `$1')define(`first1', `_1($@@)1') +@result{} +dnl Eleventh argument, portable +define(`_9', `$9')define(`eleventh', `_9(shift(shift($@@)))') +@result{} +dnl Eleventh argument, GNU style +define(`Eleventh', `$11') +@result{} +first1(`a', `b', `c', `d', `e', `f', `g', `h', `i', `j', `k') +@result{}A1 +eleventh(`a', `b', `c', `d', `e', `f', `g', `h', `i', `j', `k') +@result{}k +Eleventh(`a', `b', `c', `d', `e', `f', `g', `h', `i', `j', `k') +@result{}k +@end example + +@noindent +Also see the @code{argn} macro (@pxref{Shift}). @item The @code{divert} (@pxref{Divert}) macro can manage more than 9 -diversions. @acronym{GNU} @code{m4} treats all positive numbers as valid +diversions. GNU @code{m4} treats all positive numbers as valid diversions, rather than discarding diversions greater than 9. @item Files included with @code{include} and @code{sinclude} are sought in a user specified search path, if they are not found in the working directory. The search path is specified by the @option{-I} option and the -@samp{M4PATH} environment variable (@pxref{Search Path}). +@env{M4PATH} environment variable (@pxref{Search Path}). @item Arguments to @code{undivert} can be non-numeric, in which case the named @@ -9179,16 +7406,10 @@ Formatted output is supported through the @code{format} builtin, which is modeled after the C library function @code{printf} (@pxref{Format}). @item -Searches and text substitution through regular expressions are supported -by the @code{regexp} (@pxref{Regexp}) and @code{patsubst} -(@pxref{Patsubst}) builtins. - -The syntax of regular expressions in M4 has never been clearly -formalized. While Open@acronym{BSD} M4 uses extended regular -expressions for @code{regexp} and @code{patsubst}, @acronym{GNU} M4 -defaults to basic regular expressions, but provides -@code{changeresyntax} (@pxref{Changeresyntax}) to change the flavor of -regular expression syntax in use. +Searches and text substitution through basic regular expressions are +supported by the @code{regexp} (@pxref{Regexp}) and @code{patsubst} +(@pxref{Patsubst}) builtins. Some BSD implementations use +extended regular expressions instead. @item The output of shell commands can be read into @code{m4} with @@ -9207,80 +7428,98 @@ line number are accessible through the builtins @code{@w{__program__}}, @code{@w{__file__}}, and @code{@w{__line__}} (@pxref{Location}). @item -The generation of sync lines can be controlled through @code{syncoutput} -(@pxref{Syncoutput}). - -@item The format of the output from @code{dumpdef} and macro tracing can be -controlled with @code{debugmode} (@pxref{Debugmode}). +controlled with @code{debugmode} (@pxref{Debug Levels}). @item The destination of trace and debug output can be controlled with -@code{debugfile} (@pxref{Debugfile}). +@code{debugfile} (@pxref{Debug Output}). @item The @code{maketemp} (@pxref{Mkstemp}) macro behaves like @code{mkstemp}, creating a new file with a unique name on every invocation, rather than following the insecure behavior of replacing the trailing @samp{X} -characters with the @code{m4} process id. @acronym{POSIX} does not -allow this extension, so @code{maketemp} is insecure if -@env{POSIXLY_CORRECT} is set, but you should be using @code{mkstemp} in -the first place. +characters with the @code{m4} process id. @item -@acronym{POSIX} only requires support for the command line options +POSIX only requires support for the command line options @option{-s}, @option{-D}, and @option{-U}, so all other options accepted -by @acronym{GNU} M4 are extensions. @xref{Invoking m4}, for a +by GNU M4 are extensions. @xref{Invoking m4}, for a description of these options. -@item -The debugging and tracing facilities in @acronym{GNU} @code{m4} are much +The debugging and tracing facilities in GNU @code{m4} are much more extensive than in most other versions of @code{m4}. +@end itemize + +@node Incompatibilities +@section Facilities in System V @code{m4} not in GNU @code{m4} + +The version of @code{m4} from System V contains a few facilities that +have not been implemented in GNU @code{m4} yet. Additionally, +POSIX requires some behaviors that GNU @code{m4} has not +implemented yet. Relying on these behaviors is non-portable, as a +future release of GNU @code{m4} may change. + +@itemize @bullet +@item +POSIX requires support for multiple arguments to @code{defn}, +without any clarification on how @code{defn} behaves when one of the +multiple arguments names a builtin. System V @code{m4} and some other +implementations allow mixing builtins and text macros into a single +macro. GNU @code{m4} only supports joining multiple text +arguments, although a future implementation may lift this restriction to +behave more like System V@. The only portable way to join text macros +with builtins is via helper macros and implicit concatenation of macro +results. + +@item +POSIX requires an application to exit with non-zero status if +it wrote an error message to stderr. This has not yet been consistently +implemented for the various builtins that are required to issue an error +(such as @code{eval} (@pxref{Eval}) when an argument cannot be parsed). @item Some traditional implementations only allow reading standard input -once, but @acronym{GNU} @code{m4} correctly handles multiple instances +once, but GNU @code{m4} correctly handles multiple instances of @samp{-} on the command line. @item -@acronym{POSIX} requires @code{m4wrap} (@pxref{M4wrap}) to act in FIFO -(first-in, first-out) order, and most other implementations obey this. -However, versions of @acronym{GNU} @code{m4} earlier than 1.6 used -LIFO order. Furthermore, @acronym{POSIX} states that only the first +POSIX requires @code{m4wrap} (@pxref{M4wrap}) to act in FIFO +(first-in, first-out) order, but GNU @code{m4} currently uses +LIFO order. Furthermore, POSIX states that only the first argument to @code{m4wrap} is saved for later evaluation, but -@acronym{GNU} @code{m4} saves and processes all arguments, with output +GNU @code{m4} saves and processes all arguments, with output separated by spaces. @item -@acronym{POSIX} states that builtins that require arguments, but are +POSIX states that builtins that require arguments, but are called without arguments, have undefined behavior. Traditional implementations simply behave as though empty strings had been passed. For example, @code{a`'define`'b} would expand to @code{ab}. But -@acronym{GNU} @code{m4} ignores certain builtins if they have missing +GNU @code{m4} ignores certain builtins if they have missing arguments, giving @code{adefineb} for the above example. -@end itemize -@node Incompatibilities -@section Other incompatibilities - -There are a few other incompatibilities between this implementation of -@code{m4}, and what @acronym{POSIX} requires, or what the System V -version implemented. - -@itemize @bullet @item Traditional implementations handle @code{define(`f',`1')} (@pxref{Define}) by undefining the entire stack of previous definitions, and if doing -@code{undefine(`f')} first. @acronym{GNU} @code{m4} replaces just the top +@code{undefine(`f')} first. GNU @code{m4} replaces just the top definition on the stack, as if doing @code{popdef(`f')} followed by -@code{pushdef(`f',`1')}. @acronym{POSIX} allows either behavior. +@code{pushdef(`f',`1')}. POSIX allows either behavior. @item -At one point, @acronym{POSIX} required @code{changequote(@var{arg})} +POSIX 2001 requires @code{syscmd} (@pxref{Syscmd}) to evaluate +command output for macro expansion, but this was a mistake that is +anticipated to be corrected in the next version of POSIX. +GNU @code{m4} follows traditional behavior in @code{syscmd} +where output is not rescanned, and provides the extension @code{esyscmd} +that does scan the output. + +@item +At one point, POSIX required @code{changequote(@var{arg})} (@pxref{Changequote}) to use newline as the close quote, but this was a -bug, and the next version of @acronym{POSIX} is anticipated to state +bug, and the next version of POSIX is anticipated to state that using empty strings or just one argument is unspecified. -Meanwhile, the @acronym{GNU} @code{m4} behavior of treating an empty +Meanwhile, the GNU @code{m4} behavior of treating an empty end-quote delimiter as @samp{'} is not portable, as Solaris treats it as repeating the start-quote delimiter, and BSD treats it as leaving the previous end-quote delimiter unchanged. For predictable results, never @@ -9288,68 +7527,128 @@ call changequote with just one argument, or with empty strings for arguments. @item -At one point, @acronym{POSIX} required @code{changecom(@var{arg},)} +At one point, POSIX required @code{changecom(@var{arg},)} (@pxref{Changecom}) to make it impossible to end a comment, but this is -a bug, and the next version of @acronym{POSIX} is anticipated to state -that using empty strings is unspecified. Meanwhile, the @acronym{GNU} +a bug, and the next version of POSIX is anticipated to state +that using empty strings is unspecified. Meanwhile, the GNU @code{m4} behavior of treating an empty end-comment delimiter as newline is not portable, as BSD treats it as leaving the previous end-comment delimiter unchanged. It is also impossible in BSD implementations to -disable comments, even though that is required by @acronym{POSIX}. For +disable comments, even though that is required by POSIX. For predictable results, never call changecom with empty strings for arguments. @item +Most implementations of @code{m4} give macros a higher precedence than +comments when parsing, meaning that if the start delimiter given to +@code{changecom} (@pxref{Changecom}) starts with a macro name, comments +are effectively disabled. POSIX does not specify what the +precedence is, so this version of GNU @code{m4} parser +recognizes comments, then macros, then quoted strings. + +@item Traditional implementations allow argument collection, but not string and comment processing, to span file boundaries. Thus, if @file{a.m4} contains @samp{len(}, and @file{b.m4} contains @samp{abc)}, @kbd{m4 a.m4 b.m4} outputs @samp{3} with traditional @code{m4}, but gives an error message that the end of file was encountered inside a -macro with @acronym{GNU} @code{m4}. On the other hand, traditional +macro with GNU @code{m4}. On the other hand, traditional implementations do end of file processing for files included with -@code{include} or @code{sinclude} (@pxref{Include}), while @acronym{GNU} +@code{include} or @code{sinclude} (@pxref{Include}), while GNU @code{m4} seamlessly integrates the content of those files. Thus @code{include(`a.m4')include(`b.m4')} will output @samp{3} instead of giving an error. @item -@acronym{POSIX} requires @code{eval} (@pxref{Eval}) to treat all +Traditional @code{m4} treats @code{traceon} (@pxref{Trace}) without +arguments as a global variable, independent of named macro tracing. +Also, once a macro is undefined, named tracing of that macro is lost. +On the other hand, when GNU @code{m4} encounters +@code{traceon} without +arguments, it turns tracing on for all existing definitions at the time, +but does not trace future definitions; @code{traceoff} without arguments +turns tracing off for all definitions regardless of whether they were +also traced by name; and tracing by name, such as with @option{-tfoo} at +the command line or @code{traceon(`foo')} in the input, is an attribute +that is preserved even if the macro is currently undefined. + +Additionally, while POSIX requires trace output, it makes no +demands on the formatting of that output. Parsing trace output is not +guaranteed to be reliable, even between different releases of +GNU M4; however, the intent is that any future changes in +trace output will only occur under the direction of additional +@code{debugmode} flags (@pxref{Debug Levels}). + +@item +POSIX requires @code{eval} (@pxref{Eval}) to treat all operators with the same precedence as C@. However, earlier versions of -@acronym{GNU} @code{m4} followed the traditional behavior of other +GNU @code{m4} followed the traditional behavior of other @code{m4} implementations, where bitwise and logical negation (@samp{~} and @samp{!}) have lower precedence than equality operators; and where equality operators (@samp{==} and @samp{!=}) had the same precedence as relational operators (such as @samp{<}). Use explicit parentheses to -ensure proper precedence. As extensions to @acronym{POSIX}, -@acronym{GNU} @code{m4} gives well-defined semantics to operations that +ensure proper precedence. As extensions to POSIX, +GNU @code{m4} gives well-defined semantics to operations that C leaves undefined, such as when overflow occurs, when shifting negative -numbers, or when performing division by zero. @acronym{POSIX} also +numbers, or when performing division by zero. POSIX also requires @samp{=} to cause an error, but many traditional implementations allowed it as an alias for @samp{==}. @item -@acronym{POSIX} 2001 requires @code{translit} (@pxref{Translit}) to +POSIX 2001 requires @code{translit} (@pxref{Translit}) to treat each character of the second and third arguments literally. -However, it is anticipated that the next version of @acronym{POSIX} will -allow the @acronym{GNU} @code{m4} behavior of treating @samp{-} as a +However, it is anticipated that the next version of POSIX will +allow the GNU @code{m4} behavior of treating @samp{-} as a range operator. @item -@acronym{POSIX} requires @code{m4} to honor the locale environment +POSIX requires @code{m4} to honor the locale environment variables of @env{LANG}, @env{LC_ALL}, @env{LC_CTYPE}, @env{LC_MESSAGES}, and @env{NLSPATH}, but this has not yet been -implemented in @acronym{GNU} @code{m4}. +implemented in GNU @code{m4}. + +@item +POSIX states that only unquoted leading newlines and blanks +(that is, space and tab) are ignored when collecting macro arguments. +However, this appears to be a bug in POSIX, since most +traditional implementations also ignore all whitespace (formfeed, +carriage return, and vertical tab). GNU @code{m4} follows +tradition and ignores all leading unquoted whitespace. @item -@acronym{GNU} @code{m4} implements sync lines differently from System V -@code{m4}, when text is being diverted. @acronym{GNU} @code{m4} outputs +@cindex @env{POSIXLY_CORRECT} +A strictly-compliant POSIX client is not allowed to use +command-line arguments not specified by POSIX. However, since +this version of M4 ignores @env{POSIXLY_CORRECT} and enables the option +@code{--gnu} by default (@pxref{Limits control, , Invoking m4}), a +client desiring to be strictly compliant has no way to disable +GNU extensions that conflict with POSIX when +directly invoking the compiled @code{m4}. A future version of +@code{GNU} M4 will honor the environment variable @env{POSIXLY_CORRECT}, +implicitly enabling @option{--traditional} if it is set, in order to +allow a strictly-compliant client. In the meantime, a client needing +strict POSIX compliance can use the workaround of invoking a +shell script wrapper, where the wrapper then adds @option{--traditional} +to the arguments passed to the compiled @code{m4}. +@end itemize + +@node Other Incompatibilities +@section Other incompatibilities + +There are a few other incompatibilities between this implementation of +@code{m4}, and the System V version. + +@itemize @bullet +@item +GNU @code{m4} implements sync lines differently from System V +@code{m4}, when text is being diverted. GNU @code{m4} outputs the sync lines when the text is being diverted, and System V @code{m4} when the diverted text is being brought back. The problem is which lines and file names should be attached to text that is being, or has been, diverted. System V @code{m4} regards all the diverted text as being generated by the source line containing the -@code{undivert} call, whereas @acronym{GNU} @code{m4} regards the +@code{undivert} call, whereas GNU @code{m4} regards the diverted text as being generated at the time it is diverted. The sync line option is used mostly when using @code{m4} as @@ -9371,7 +7670,6 @@ divert`'0 @result{}2 @end example -@comment FIXME - this needs to be fixed before 2.0. The current @code{m4} implementation has a limitation that the syncline output at the start of each diversion occurs no matter what, even if the previous diversion did not end with a newline. This goes contrary to @@ -9381,10 +7679,9 @@ meantime, when using @option{-s}, it is wisest to make sure all diversions end with newline. @item -@acronym{GNU} @code{m4} makes no attempt at prohibiting self-referential +GNU @code{m4} makes no attempt at prohibiting self-referential definitions like: -@comment ignore @example define(`x', `x') @result{} @@ -9407,48 +7704,11 @@ ifelse(defn(`@var{holder}'), `@var{value}', @dots{}) @noindent In cases like this one, an interdiction for a macro to hold its own name would be a useless limitation. Of course, this leaves more rope for the -@acronym{GNU} @code{m4} user to hang himself! Rescanning hangs may be +GNU @code{m4} user to hang himself! Rescanning hangs may be avoided through careful programming, a little like for endless loops in traditional programming languages. - -@item -@acronym{POSIX} states that only unquoted leading newlines and blanks -(that is, space and tab) are ignored when collecting macro arguments. -However, this appears to be a bug in @acronym{POSIX}, since most -traditional implementations also ignore all whitespace (formfeed, -carriage return, and vertical tab). @acronym{GNU} @code{m4} follows -tradition and ignores all leading unquoted whitespace. @end itemize -@node Experiments -@section Experimental features in @acronym{GNU} M4 - -Certain features of GNU @code{m4} are experimental. - -Some are only available if activated by an option given to -@file{m4-@value{VERSION}/@/configure} at GNU @code{m4} installation -time. The functionality -might change or even go away in the future. @emph{Do not rely on it}. -Please direct your comments about it the same way you would do for bugs. - -@section Changesyntax - -An experimental feature, which improves the flexibility of @code{m4}, -allows for changing the way the input is parsed (@pxref{Changesyntax}). -No compile time option is needed for @code{changesyntax}. The -implementation is careful to not slow down @code{m4} parsing, unlike the -withdrawn experiment of @code{changeword} that appeared earlier in M4 -1.4.x. - -@section Multiple precision arithmetic - -Another experimental feature, which would improve @code{m4} usefulness, -allows for multiple precision rational arithmetic similar to -@code{eval}. You must have the @acronym{GNU} multi-precision (gmp) -library installed, and should use @kbd{./configure --with-gmp} if you -want this feature compiled in. The current implementation is unproven -and might go away. Do not count on it yet. - @node Answers @chapter Correct version of some examples @@ -9499,7 +7759,7 @@ per iteration (excluding those in @var{text}), by not dereferencing the @comment examples @example -$ @kbd{m4 -I examples} +$ @kbd{m4 -d -I examples} undivert(`forloop2.m4')dnl @result{}divert(`-1') @result{}# forloop(var, from, to, stmt) - improved version: @@ -9522,7 +7782,7 @@ forloop(`', `1', `2', ` odd iterator name') forloop(`i', `5 + 5', `0xc', ` 0x`'eval(i, `16')') @result{} 0xa 0xb 0xc forloop(`i', `a', `b', `non-numeric bounds') -@error{}m4:stdin:6: warning: eval: bad input: `(a) <= (b)' +@error{}m4:stdin:6: bad expression in eval (bad input): (a) <= (b) @result{} @end example @@ -9622,7 +7882,7 @@ popdef(`a')a Of course, it is possible to make even more improvements, such as adding an optional step argument, or allowing iteration through -descending sequences. @acronym{GNU} Autoconf provides some of these +descending sequences. GNU Autoconf provides some of these additional bells and whistles in its @code{m4_for} macro. @node Improved foreach @@ -9713,17 +7973,18 @@ helper method immediately, the @samp{defn(`@var{iterator}')} no longer contains unexpanded macros. The astute m4 programmer might notice that the solution above still uses -more macro invocations than strictly necessary. Note that @samp{$2}, -which contains an arbitrarily long quoted list, is expanded and -rescanned three times per iteration of @code{_foreachq}. Furthermore, -every iteration of the algorithm effectively unboxes then reboxes the -list, which costs a couple of macro invocations. It is possible to -rewrite the algorithm by swapping the order of the arguments to -@code{_foreachq} in order to operate on an unboxed list in the first -place, and by using the fixed-length @samp{$#} instead of an arbitrary -length list as the key to end recursion. The result is an overhead of -six macro invocations per loop (excluding any macros in @var{text}), -instead of eight. This alternative approach is available as +more memory and macro invocations, and thus more time, than strictly +necessary. Note that @samp{$2}, which contains an arbitrarily long +quoted list, is expanded and rescanned three times per iteration of +@code{_foreachq}. Furthermore, every iteration of the algorithm +effectively unboxes then reboxes the list, which costs a couple of macro +invocations. It is possible to rewrite the algorithm for a bit more +speed by swapping the order of the arguments to @code{_foreachq} in +order to operate on an unboxed list in the first place, and by using the +fixed-length @samp{$#} instead of an arbitrary length list as the key to +end recursion. The result is an overhead of six macro invocations per +loop (excluding any macros in @var{text}), instead of eight. This +alternative approach is available as @file{m4-@value{VERSION}/@/examples/@/foreach3.m4}: @comment examples @@ -9771,17 +8032,16 @@ foreachq(`x', ``1', `2', `3', `4'', `x @error{}m4trace: -2- shift(`3', `4') @end example -Prior to M4 1.6, every instance of @samp{$@@} was rescanned as it was -encountered. Thus, the @file{foreachq3.m4} alternative used much less -memory than @file{foreachq2.m4}, and executed as much as 10% faster, -since each iteration encountered fewer @samp{$@@}. However, the -implementation of rescanning every byte in @samp{$@@} was quadratic in +In the current version of M4, every instance of @samp{$@@} is rescanned +as it is encountered. Thus, the @file{foreachq3.m4} alternative uses +much less memory than @file{foreachq2.m4}, and executes as much as 10% +faster, since each iteration encounters fewer @samp{$@@}. However, the +implementation of rescanning every byte in @samp{$@@} is quadratic in the number of bytes scanned (for example, making the broken version in -@file{foreachq.m4} cubic, rather than quadratic, in behavior). Once the -underlying M4 implementation was improved in 1.6 to reuse results of -previous scans, both styles of @code{foreachq} become linear in the -number of bytes scanned, but the @file{foreachq3.m4} version remains -noticeably faster because of fewer macro invocations. Notice how the +@file{foreachq.m4} cubic, rather than quadratic, in behavior). A future +release of M4 will improve the underlying implementation by reusing +results of previous scans, so that both styles of @code{foreachq} can +become linear in the number of bytes scanned. Notice how the implementation injects an empty argument prior to expanding @samp{$2} within @code{foreachq}; the helper macro @code{_foreachq} then ignores the third argument altogether, and ends recursion when there are three @@ -9798,7 +8058,7 @@ each iteration parses a constant amount of arguments. So, it is possible to design a variant that uses @code{forloop} to do the iteration, then uses @samp{$@@} only once at the end, giving a linear result even with older M4 implementations. This implementation relies -on the @acronym{GNU} extension that @samp{$10} expands to the tenth +on the GNU extension that @samp{$10} expands to the tenth argument rather than the first argument concatenated with @samp{0}. The trick is to define an intermediate macro that repeats the text @code{m4_define(`$1', `$@var{n}')$2`'}, with @samp{n} set to successive @@ -9806,17 +8066,13 @@ integers corresponding to each argument. The helper macro @code{_foreachq_} is needed in order to generate the literal sequences such as @samp{$1} into the intermediate macro, rather than expanding them as the arguments of @code{_foreachq}. With this approach, no -@code{shift} calls are even needed! However, when linear recursion is -available in new enough M4, the time and memory cost of using -@code{forloop} to build an intermediate macro outweigh the costs of any -of the previous implementations (there are seven macros of overhead per -iteration instead of six in @file{foreachq3.m4}, and the entire -intermediate macro must be built in memory before any iteration is -expanded). Additionally, this approach will need adjustment when a -future version of M4 follows @acronym{POSIX} by no longer treating -@samp{$10} as the tenth argument; the anticipation is that -@samp{$@{10@}} can be used instead, although that alternative syntax is -not yet supported. +@code{shift} calls are even needed! Even though there are seven macros +of overhead per iteration instead of six in @file{foreachq3.m4}, the +linear scaling is apparent at relatively small list sizes. However, +this approach will need adjustment when a future version of M4 follows +POSIX by no longer treating @samp{$10} as the tenth argument; +the anticipation is that @samp{$@{10@}} can be used instead, although +that alternative syntax is not yet supported. @comment examples @example @@ -9892,39 +8148,6 @@ performs in linear time on M4 1.4.x; the easiest method is probably writing a version of @code{foreach} that unboxes its list, then invokes @code{_foreachq} as previously defined in @file{foreachq4.m4}. -@cindex filtering defined symbols -@cindex subset of defined symbols -@cindex defined symbols, filtering -With a robust @code{foreachq} implementation, it is possible to create a -filter on a list of defined symbols. This next example will find all -symbols that contain @samp{if} or @samp{def}, via two different -approaches. In the first approach, @code{dquote_elt} is used to -overquote each list element, then @code{dquote} forms the list; that -way, the iterator @code{macro} can be expanded in place because its -contents are already quoted. This approach also uses a self-modifying -macro @code{sep} to provide the correct number of commas. In the second -approach, the iterator @code{macro} contains live text, so it must be -used with @code{defn} to avoid unintentional expansion. The correct -number of commas is achieved by using @code{shift} to ignore the first -one, although a leading space still remains. - -@comment examples -@example -$ @kbd{m4 -I examples} -include(`quote.m4')include(`foreachq2.m4') -@result{} -pushdef(`sep', `define(`sep', ``, '')') -@result{} -foreachq(`macro', dquote(dquote_elt(m4symbols)), - `regexp(macro, `.*if.*', `sep`\&'')') -@result{}ifdef, ifelse, shift -popdef(`sep') -@result{} -shift(foreachq(`macro', dquote(m4symbols), - `regexp(defn(`macro'), `def', `,` ''dquote(defn(`macro')))')) -@result{} define, defn, dumpdef, ifdef, popdef, pushdef, undefine -@end example - In summary, recursion over list elements is trickier than it appeared at first glance, but provides a powerful idiom within @code{m4} processing. As a final demonstration, both list styles are now able to handle @@ -9943,7 +8166,7 @@ detrimental effects. @comment examples @example -$ @kbd{m4 -d -I examples} +$ @kbd{m4 -I examples} include(`foreach2.m4') @result{} include(`foreachq2.m4') @@ -10014,10 +8237,65 @@ foreachq(`x', ```active'', ``active''', `<x> @result{}<active> @end example +@ignore +@comment Not worth putting in the manual, but make sure that foreach +@comment implementations behave, and that final implementation is +@comment linear. + +@comment boxed recursion + +@comment examples +@comment options: -Dlimit=10 -Dverbose +@example +$ @kbd {m4 -I examples -Dlimit=10 -Dverbose} +include(`loop.m4')dnl +@result{} 1 2 3 4 5 6 7 8 9 10 +@end example + +@comment unboxed recursion + +@comment examples +@comment options: -Dlimit=10 -Dverbose -Dalt +@example +$ @kbd {m4 -I examples -Dlimit=10 -Dverbose -Dalt} +include(`loop.m4')dnl +@result{} 1 2 3 4 5 6 7 8 9 10 +@end example + +@comment foreach via forloop recursion + +@comment examples +@comment options: -Dlimit=10 -Dverbose -Dalt=4 +@example +$ @kbd {m4 -I examples -Dlimit=10 -Dverbose -Dalt=4} +include(`loop.m4')dnl +@result{} 1 2 3 4 5 6 7 8 9 10 +@end example + +@comment examples +@comment options: -Dlimit=2500 -Dalt=4 +@example +$ @kbd {m4 -I examples -Dlimit=2500 -Dalt=4} +include(`loop.m4')dnl +@end example + +@comment examples +@comment options: -Dlimit=10000 -Dalt=4 +@example +$ @kbd {m4 -I examples -Dlimit=10000 -Dalt=4} +define(`foo', `divert`'len(popdef(`_foreachq')_foreachq($@@))')dnl +define(`debug', `pushdef(`_foreachq', defn(`foo'))') +@result{} +include(`loop.m4')dnl +@result{}48894 +@end example + +@end ignore + @node Improved copy @section Solution for @code{copy} -The macro @code{copy} presented above works with M4 1.6 and newer, but +The macro @code{copy} presented above is unable to handle builtin tokens with M4 1.4.x, because it tries to pass the builtin token through the macro @code{curry}, where it is silently flattened to an empty string (@pxref{Composition}). Rather @@ -10107,6 +8385,23 @@ undivert(`stack_sep.m4')dnl @result{}divert`'dnl @end example +@ignore +@comment Not worth putting in the manual, but make sure that +@comment stack_foreach_sep has linear performance. + +@comment examples +@example +$ @kbd {m4 -I examples} +include(`forloop3.m4')include(`stack_sep.m4')dnl +forloop(`i', `1', `10000', `pushdef(`s', i)') +@result{} +define(`colon', `:')define(`dash', `-') +@result{} +len(stack_foreach_sep(`s', `dash', `', `colon')) +@result{}58893 +@end example +@end ignore + @node Improved m4wrap @section Solution for @code{m4wrap} @@ -10129,8 +8424,8 @@ builtin(`m4wrap', ``'define(`bar', ``$0:'-$1-$*-$#-')bar(`a', `b') ') @result{} ^D -@result{}m4wrap0:---0- @result{}bar:-a-a,b-2- +@result{}m4wrap0:---0- @end example Additionally, the computation of @code{_m4wrap_level} and creation of @@ -10142,7 +8437,7 @@ stripping a level of quotes with @code{_arg1} to expand the text. That way, each level of wrapping reuses the single placeholder, which starts each nesting level in an undefined state. -Finally, it is worth emulating the @acronym{GNU} M4 extension of saving +Finally, it is worth emulating the GNU M4 extension of saving all arguments to @code{m4wrap}, separated by a space, rather than saving just the first argument. This is done with the @code{join} macro documented previously (@pxref{Shift}). The improved LIFO example is @@ -10285,7 +8580,7 @@ string. In turn, that means the replacement text has unbalanced quotes, necessitating another round of @code{changequote}. In the fixed version below, (also shipped as -@file{m4-@value{VERSION}/@/examples/@/capitalize.m4}), @code{capitalize} +@file{m4-@value{VERSION}/@/examples/@/capitalize2.m4}), @code{capitalize} uses the alternate quotes of @samp{<<[} and @samp{]>>} (the longer strings are chosen so as to be less likely to appear in the text being converted). The helpers @code{_to_alt} and @code{_from_alt} merely @@ -10335,7 +8630,7 @@ undivert(`capitalize2.m4')dnl @section Solution for @code{fatal_error} The @code{fatal_error} macro (@pxref{M4exit}) is not robust to versions -of @acronym{GNU} M4 earlier than 1.4.8, where invoking +of GNU M4 earlier than 1.4.8, where invoking @code{@w{__file__}} (@pxref{Location}) inside @code{m4wrap} would result in an empty string, and @code{@w{__line__}} resulted in @samp{0} even though all files start at line 1. Furthermore, versions earlier than @@ -10355,7 +8650,7 @@ m4wrap(`divnum(`demo of internal message') fatal_error(`inside wrapped text')') @result{} ^D -@error{}m4:stdin:6: warning: divnum: extra arguments ignored: 1 > 0 +@error{}m4:stdin:6: Warning: excess arguments to builtin `divnum' ignored @result{}0 @error{}m4:stdin:6: fatal error: inside wrapped text @end example @@ -10426,6 +8721,7 @@ macro is introduced the first time. @bye @c Local Variables: +@c coding: iso-8859-1 @c fill-column: 72 @c ispell-local-dictionary: "american" @c indent-tabs-mode: nil diff --git a/doc/stamp-vti b/doc/stamp-vti new file mode 100644 index 00000000..75abce44 --- /dev/null +++ b/doc/stamp-vti @@ -0,0 +1,4 @@ +@set UPDATED 28 February 2011 +@set UPDATED-MONTH February 2011 +@set EDITION 1.4.16 +@set VERSION 1.4.16 diff --git a/doc/version.texi b/doc/version.texi new file mode 100644 index 00000000..75abce44 --- /dev/null +++ b/doc/version.texi @@ -0,0 +1,4 @@ +@set UPDATED 28 February 2011 +@set UPDATED-MONTH February 2011 +@set EDITION 1.4.16 +@set VERSION 1.4.16 |