* doc/autoconf.texi (C and Posix Variants, System Services): Remind user to include config.h first. (Configuration Headers): Give another reason why config.h must be first, and mention that only .c files need it. Based on discussion on bugs.debian.org/158969
Signed-off-by: Eric Blake <ebl...@redhat.com> --- I'm still waiting for mirabilos to post an updated version of his patch to AC_SYS_LARGEFILE docs, but my contribution seems to be worth pushing on its own right now, once I've expanded it to cover more places as mentioned by Zack. doc/autoconf.texi | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-) diff --git a/doc/autoconf.texi b/doc/autoconf.texi index 07f238d..e510323 100644 --- a/doc/autoconf.texi +++ b/doc/autoconf.texi @@ -3268,7 +3268,12 @@ Configuration Headers The package should @samp{#include} the configuration header file before any other header files, to prevent inconsistencies in declarations (for -example, if it redefines @code{const}). +example, if it redefines @code{const}, or if it defines a macro like +@code{_FILE_OFFSET_BITS} that affects the behavior of system +headers). Note that it is okay to only include @file{config.h} from +@file{.c} files; the project's @file{.h} files can rely on +@file{config.h} already being included first by the corresponding +@file{.c} file. To provide for VPATH builds, remember to pass the C compiler a @option{-I.} option (or @option{-I..}; whichever directory contains @file{config.h}). @@ -8595,7 +8600,9 @@ System Services @code{off_t} is wider than @code{long int}, since this is common when large-file support is enabled. For example, it is not correct to print an arbitrary @code{off_t} value @code{X} with @code{printf ("%ld", -(long int) X)}. +(long int) X)}. Also, when using this macro in concert with +@code{AC_CONFIG_HEADERS}, be sure that @file{config.h} is included +before any system header. The LFS introduced the @code{fseeko} and @code{ftello} functions to replace their C counterparts @code{fseek} and @code{ftell} that do not @@ -8632,11 +8639,13 @@ C and Posix Variants @anchor{AC_USE_SYSTEM_EXTENSIONS} @defmac AC_USE_SYSTEM_EXTENSIONS @acindex{USE_SYSTEM_EXTENSIONS} -If possible, enable -extensions to C or Posix on hosts that normally disable the extensions, -typically due to standards-conformance namespace issues. This should be -called before any macros that run the C compiler. The following -preprocessor macros are defined where appropriate: +If possible, enable extensions to C or Posix on hosts that normally +disable the extensions, typically due to standards-conformance namespace +issues. This should be called before any macros that run the C +compiler. Also, when using this macro in concert with +@code{AC_CONFIG_HEADERS}, be sure that @file{config.h} is included +before any system header. The following preprocessor macros are defined +where appropriate: @table @code @item _GNU_SOURCE -- 2.9.3