As C23 is now mostly supported by GCC, it's time for
AC_PROG_CC to prefer C23 if available.
* lib/autoconf/c.m4 (_AC_C_C23_TEST_GLOBALS, _AC_C_C23_TEST_MAIN):
(_AC_C_C23_TEST_PROGRAM, _AC_C_C23_OPTIONS): New macros.
(_AC_PROG_CC_STDC_EDITION): Try C23 first.
Problems reported by Antonin Décimo in: https://lists.gnu.org/r/autoconf/2024-04/msg00001.html
* lib/autoconf/c.m4 (_AC_C_C89_TEST_GLOBALS):
Do not test the value of __STDC__.
(_AC_C_C99_TEST_MAIN): Do not test for VLAs.
(_AC_C_C11_OPTIONS): Also test -std:c11.
Problem reported by Zack Weinberg
<https://savannah.gnu.org/support/?110983>.
* lib/autoconf/specific.m4 (_AC_SYS_YEAR2038_PROBE)
(_AC_SYS_LARGEFILE_PROBE):
In chatter, say it’s a CPPFLAGS option, not a CC option.
(_AC_SYS_LARGEFILE_OPTIONS): Omit -n32, as we no longer
need to worry about IRIX.
(_AC_SYS_LARGEFILE_PROBE): Fiddle with CPPFLAGS, not CC,
and don’t worry about -n32.
Simplified version of a suggestion by Reuben Thomas in: https://lists.gnu.org/r/bug-autoconf/2024-04/msg00021.html
* bin/autom4te.in (warn_forbidden): Change message wording.
* tests/tools.at (autom4te and whitespace in file names)
(forbidden tokens, exceptions): Adjust tests to match new behavior.