configure: new option --enable-gcc-warnings

I have been using this change for many months in my private copy
of Emacs, and have used it to find several bugs.  It's mature
enough to publish now.
* Makefile.in (GNULIB_MODULES): Add warnings, manywarnings.
* configure.in: Support --enable-gcc-warnings, in the style of
other GNU packages such as coreutils.
(C_WARNINGS_SWITCH): Remove, replacing with...
(WARN_CFLAGS, GNULIB_WARN_CFLAGS): New variable.
(PKG_CHECK_MODULES, C_SWITCH_X_SITE): Use -isystem rather than -I,
when including system files with GCC.
* etc/NEWS: Mention --enable-gcc-warnings.
* lib/Makefile.am (AM_CFLAGS): New macro.
* m4/manywarnings.m4, m4/warnings.m4: New files, from gnulib.
* lib-src/Makefile.in (C_WARNINGS_SWITCH): Remove.
(WARN_CFLAGS, WERROR_CFLAGS): New macros.
(BASE_CFLAGS): Use new macros rather than old.
* lwlib/Makefile.in (C_WARNINGS_SWITCH): Remove.
(WARN_CFLAGS, WERROR_CFLAGS): New macros.
(ALL_CFLAGS): Use new macros rather than old.
* oldXMenu/Makefile.in (C_WARNINGS_SWITCH): Remove.
(WARN_CFLAGS, WERROR_CFLAGS): New macros.
(ALL_CFLAGS): Use new macros rather than old.
* src/Makefile.in (C_WARNINGS_SWITCH): Remove.
(WARN_CFLAGS, WERROR_CFLAGS): New macros.
(ALL_CFLAGS): Use new macros rather than old.
* src/process.c: Ignore -Wstrict-overflow to work around GCC bug 52904.
* src/regex.c: Ignore -Wstrict-overflow.  If !emacs, also ignore
-Wunused-but-set-variable, -Wunused-function, -Wunused-macros,
-Wunused-result, -Wunused-variable.  This should go away once
the Emacs and Gnulib regex code is merged.
(xmalloc, xrealloc): Now static.

4 files changed, 38 insertions, 4 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index dbff8e35492..df3336b52e1 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,18 @@
 2012-04-09  Paul Eggert  <eggert@cs.ucla.edu>
 
+	configure: new option --enable-gcc-warnings
+	* Makefile.in (C_WARNINGS_SWITCH): Remove.
+	(WARN_CFLAGS, WERROR_CFLAGS): New macros.
+	(ALL_CFLAGS): Use new macros rather than old.
+	* process.c: Ignore -Wstrict-overflow to work around GCC bug 52904.
+	* regex.c: Ignore -Wstrict-overflow.  If !emacs, also ignore
+	-Wunused-but-set-variable, -Wunused-function, -Wunused-macros,
+	-Wunused-result, -Wunused-variable.  This should go away once
+	the Emacs and Gnulib regex code is merged.
+	(xmalloc, xrealloc): Now static.
+
+2012-04-09  Paul Eggert  <eggert@cs.ucla.edu>
+
 	composite.c: use 'double' consistently
 	* composite.c (get_composition_id): Use 'double' consistently
 	instead of converting 'float' to 'double' and vice versa; this is
diff --git a/src/Makefile.in b/src/Makefile.in
index 8c3704f830e..19f586396cb 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -68,7 +68,8 @@ OTHER_FILES = @OTHER_FILES@
 PROFILING_CFLAGS = @PROFILING_CFLAGS@
 
 ## Flags to pass to the compiler to enable build warnings
-C_WARNINGS_SWITCH = @C_WARNINGS_SWITCH@
+WARN_CFLAGS = @WARN_CFLAGS@
+WERROR_CFLAGS = @WERROR_CFLAGS@
 
 ## Machine-specific CFLAGS.
 C_SWITCH_MACHINE=@C_SWITCH_MACHINE@
@@ -314,7 +315,7 @@ ALL_CFLAGS=-Demacs -DHAVE_CONFIG_H $(MYCPPFLAGS) -I. -I$(srcdir) \
   $(SETTINGS_CFLAGS) $(FREETYPE_CFLAGS) $(FONTCONFIG_CFLAGS) \
   $(LIBOTF_CFLAGS) $(M17N_FLT_CFLAGS) $(DEPFLAGS) $(PROFILING_CFLAGS) \
   $(LIBGNUTLS_CFLAGS) \
-  $(C_WARNINGS_SWITCH) $(CFLAGS)
+  $(WARN_CFLAGS) $(WERROR_CFLAGS) $(CFLAGS)
 ALL_OBJC_CFLAGS=$(ALL_CFLAGS) $(GNU_OBJC_CFLAGS)
 
 .SUFFIXES: .m
diff --git a/src/process.c b/src/process.c
index f2f33a9eafc..f14de474ee0 100644
--- a/src/process.c
+++ b/src/process.c
@@ -120,6 +120,13 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "nsterm.h"
 #endif
 
+/* Work around GCC 4.7.0 bug with strict overflow checking; see
+   <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52904>.
+   These lines can be removed once the GCC bug is fixed.  */
+#if (__GNUC__ == 4 && 3 <= __GNUC_MINOR__) || 4 < __GNUC__
+# pragma GCC diagnostic ignored "-Wstrict-overflow"
+#endif
+
 Lisp_Object Qeuid, Qegid, Qcomm, Qstate, Qppid, Qpgrp, Qsess, Qttname, Qtpgid;
 Lisp_Object Qminflt, Qmajflt, Qcminflt, Qcmajflt, Qutime, Qstime, Qcstime;
 Lisp_Object Qcutime, Qpri, Qnice, Qthcount, Qstart, Qvsize, Qrss, Qargs;
diff --git a/src/regex.c b/src/regex.c
index 0f9150193ec..d16a5148054 100644
--- a/src/regex.c
+++ b/src/regex.c
@@ -33,6 +33,19 @@
   #pragma alloca
 #endif
 
+/* Ignore some GCC warnings for now.  This section should go away
+   once the Emacs and Gnulib regex code is merged.  */
+#if (__GNUC__ == 4 && 3 <= __GNUC_MINOR__) || 4 < __GNUC__
+# pragma GCC diagnostic ignored "-Wstrict-overflow"
+# ifndef emacs
+#  pragma GCC diagnostic ignored "-Wunused-but-set-variable"
+#  pragma GCC diagnostic ignored "-Wunused-function"
+#  pragma GCC diagnostic ignored "-Wunused-macros"
+#  pragma GCC diagnostic ignored "-Wunused-result"
+#  pragma GCC diagnostic ignored "-Wunused-variable"
+# endif
+#endif
+
 #ifdef HAVE_CONFIG_H
 # include <config.h>
 #endif
@@ -198,7 +211,7 @@
 
 /* When used in Emacs's lib-src, we need xmalloc and xrealloc. */
 
-void *
+static void *
 xmalloc (size_t size)
 {
   register void *val;
@@ -211,7 +224,7 @@ xmalloc (size_t size)
   return val;
 }
 
-void *
+static void *
 xrealloc (void *block, size_t size)
 {
   register void *val;