diff options
Diffstat (limited to 'doc/autoconf.texi')
| -rw-r--r-- | doc/autoconf.texi | 50 |
1 files changed, 35 insertions, 15 deletions
diff --git a/doc/autoconf.texi b/doc/autoconf.texi index 01af2b29..cdd056c5 100644 --- a/doc/autoconf.texi +++ b/doc/autoconf.texi @@ -4070,17 +4070,14 @@ Expand to @var{include-directives} if present and nonempty, otherwise to: @example @group #include <stddef.h> -#include <stdio.h> -#include <stdlib.h> -#include <string.h> -#ifdef HAVE_SYS_TYPES_H -# include <sys/types.h> +#ifdef HAVE_STDIO_H +# include <stdio.h> #endif -#ifdef HAVE_SYS_STAT_H -# include <sys/stat.h> +#ifdef HAVE_STDLIB_H +# include <stdlib.h> #endif -#ifdef HAVE_STRINGS_H -# include <strings.h> +#ifdef HAVE_STRING_H +# include <string.h> #endif #ifdef HAVE_INTTYPES_H # include <inttypes.h> @@ -4088,6 +4085,15 @@ Expand to @var{include-directives} if present and nonempty, otherwise to: #ifdef HAVE_STDINT_H # include <stdint.h> #endif +#ifdef HAVE_STRINGS_H +# include <strings.h> +#endif +#ifdef HAVE_SYS_TYPES_H +# include <sys/types.h> +#endif +#ifdef HAVE_SYS_STAT_H +# include <sys/stat.h> +#endif #ifdef HAVE_UNISTD_H # include <unistd.h> #endif @@ -4095,12 +4101,26 @@ Expand to @var{include-directives} if present and nonempty, otherwise to: @end example Using this macro without @var{include-directives} has the side effect of -checking for @file{sys/types.h}, @file{sys/stat.h}, @file{strings.h}, -@file{inttypes.h}, @file{stdint.h}, and @file{unistd.h}, as if by -@code{AC_CHECK_HEADERS}. For backward compatibility's sake, it also -unconditionally defines @code{HAVE_STRING_H}, @code{HAVE_STDLIB_H}, and -@code{STDC_HEADERS}. New code should not make use of these preprocessor -macros. +checking for @file{stdio.h}, @file{stdlib.h}, @file{string.h}, +@file{inttypes.h}, @file{stdint.h}, @file{strings.h}, +@file{sys/types.h}, @file{sys/stat.h}, and @file{unistd.h}, as if by +@code{AC_CHECK_HEADERS_ONCE}. For backward compatibility, the macro +@code{STDC_HEADERS} will be defined when both @file{stdlib.h} and +@file{string.h} are available. + +@strong{Portability Note:} It is safe for most programs to assume the +presence of all of the headers required by the original 1990 C standard. +@code{AC_INCLUDES_DEFAULT} checks for @file{stdio.h}, @file{stdlib.h}, +and @file{string.h}, even though they are in that list, because they +might not be available when compiling for a ``freestanding environment'' +(in which most of the features of the C library are optional). You +probably do not need to write @samp{#ifdef HAVE_STDIO_H} in your own +code. + +@file{inttypes.h} and @file{stdint.h} were added to C in the 1999 +revision of the standard, and @file{strings.h}, @file{sys/types.h}, +@file{sys/stat.h}, and @file{unistd.h} are POSIX extensions. You +@emph{should} guard uses of these headers with appropriate conditionals. @end defmac @defmac AC_CHECK_INCLUDES_DEFAULT |