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Zack Weinberg 2d0f19d84d
Restore compatibility with older std-gnu11.m4.
Gnulib’s std-gnu11.m4 backports C11 and C++11 detection to autoconf
2.69.  It does this by replacing the definitions of AC_PROC_CC and
AC_PROG_CXX and most of their subroutines.  In particular, it replaces
the definitions of _AC_PROG_CC_C11, _AC_PROG_CC_C99, and _AC_C_STD_TRY,
but it does *not* replace the definition of _AC_PROG_CC_C89.

Autoconf commit 131d8c69f3 changed the
calling convention of _AC_C_STD_TRY, and changed the internal
definitions of _AC_PROG_CC_C{11,99,89} to match.  If std-gnu11.m4 is
in use, our _AC_PROG_CC_C89 calls their _AC_C_STD_TRY with the new
calling convention, and this produces a syntactically invalid
configure script.  (This is is fortunate: it could easily have been a
runtime malfunction that only manifested with compilers that only
implement C89, and then we might not have noticed the problem for
years.)

Gnulib commit a3b3fc85e3e632374811b27cb2111e50fa177e36 makes
std-gnu11.m4 do nothing when used with autoconf >=2.70, but older
versions of the file will circulate for years to come, so this patch
works around the problem in autoconf.  It does this by renaming all of
the internal macros involved with C and C++ standard edition
detection, *except* _AC_PROG_CC_C89.  AC_PROG_CC now calls
_AC_PROG_CC_STDC_EDITION, which loops over all supported editions
calling _AC_PROG_CC_STDC_EDITION_TRY, which uses the data provided by
the existing _AC_C_C${edition}_TEST_PROGRAM macros and a new set of
macros called _AC_C_C${edition}_OPTIONS to perform the test for that
edition of the standard.  Similarly, AC_PROG_CXX calls
_AC_PROG_CXX_STDCXX_EDITION, which loops calling
_AC_PROG_CXX_STDCXX_EDITION_TRY, which uses data from
_AC_CXX_CXX${edition}_TEST_PROGRAM and _AC_CXX_CXX${edition}_OPTIONS.

_AC_PROG_CC_C89 is the only macro from the old set that we still
define, and its definition is reverted to what std-gnu11.m4 expects it
to be.  Nothing in Autoconf proper uses it anymore.

foreign.at grows a test to verify that the compatibility stub version
of _AC_PROG_CC_C89 does its job.  Since this is now the third test
involving an embedded copy of a third-party macro, I broke them all
out of foreign.at to separate files in test/data/.

In addition to fixing the breakage, this patch should make it easier
to extend C / C++ standard edition detection in the future, by getting
rid of the if-else chains in AC_PROG_CC/CXX and by disentangling the
lists of command-line options to test from the logic.

I also changed the manual to suggest people refer to the variables
‘ac_prog_cc_stdc’ and ‘ac_prog_cxx_stdcxx’ to learn which edition
of the C and C++ standards are selected; these are much easier to
work with than the ac_cv_prog_cc_cNN cache variables.

* lib/autoconf/c.m4 (_AC_C_STD_TRY, _AC_PROG_CC_C99, _AC_PROG_CC_C11)
  (_AC_CXX_STD_TRY, _AC_PROG_CXX_CXX98, _AC_PROG_CXX_CXX11): Remove macro.

  (_AC_C_C89_OPTIONS, _AC_C_C99_OPTIONS, _AC_C_C11_OPTIONS)
  (_AC_PROG_CC_STDC_EDITION, _AC_PROG_CC_STDC_EDITION_TRY)
  (_AC_CXX_CXX98_OPTIONS, _AC_CXX_CXX11_OPTIONS)
  (_AC_PROG_CXX_STDCXX_EDITION, _AC_PROG_CXX_STDCXX_EDITION_TRY): New macros.

  (_AC_PROG_CC_C89): Convert to compatibility stub for std-gnu11.m4.

  (AC_PROG_CC): Use _AC_PROG_CC_STDC_EDITION.
  (AC_PROG_CXX): Use _AC_PROG_CXX_STDCXX_EDITION.

* tests/data/ax_prog_cc_for_build_v18.m4
* tests/data/ax_prog_cxx_for_build_v3.m4
* tests/data/gnulib_std_gnu11_2020_08_17.m4: New files.
* tests/foreign.at (AX_PROG_CC_FOR_BUILD, AX_PROG_CXX_FOR_BUILD):
  Remove embedded copy of ax_prog_cc_for_build_v18.m4,
  ax_prog_cxx_for_build_v3.m4 respectively.
  (gnulib-std-gnu11.m4): New test.
* tests/local.mk: Distribute tests/data/*.m4.

* doc/autoconf.texi (AC_PROG_CC, AC_PROG_CXX): Document use of
  ac_prog_cc_stdc / ac_prog_cxx_stdcxx, respectively, to tell which
  edition of the C / C++ standards are selected, instead of looking
  through a series of cache variables with awkward definitions.
2020-12-23 13:42:28 -05:00
bin autom4te: correct error message when we can’t create autom4te.cache. 2020-12-23 13:12:51 -05:00
build-aux make fetch 2020-12-07 17:23:37 -05:00
doc Restore compatibility with older std-gnu11.m4. 2020-12-23 13:42:28 -05:00
lib Restore compatibility with older std-gnu11.m4. 2020-12-23 13:42:28 -05:00
m4 make fetch 2020-09-03 12:08:31 -04:00
man Generate manpages directly from source code. 2020-08-21 16:23:32 -04:00
tests Restore compatibility with older std-gnu11.m4. 2020-12-23 13:42:28 -05:00
.gitattributes maint: don't sync elisp-comp or missing from gnulib 2012-06-27 16:59:21 -06:00
.gitignore Check in install-sh as synced from automake (#110368) 2020-11-09 13:51:20 -05:00
.prev-version maint: post-release administrivia 2020-12-08 13:04:16 -05:00
.x-update-copyright maint: document use of copyright ranges 2011-01-04 16:32:25 -07:00
AUTHORS maint: make update-copyright 2020-01-01 11:45:50 -08:00
BUGS BUGS: Remove mention of old shells lacking functions. 2020-08-28 16:44:59 -04:00
cfg.mk maint: post-release administrivia 2020-12-08 13:04:16 -05:00
ChangeLog.0 Prefer HTTPS to FTP and HTTP 2017-09-16 17:48:51 -07:00
ChangeLog.1 Prefer HTTPS to FTP and HTTP 2017-09-16 17:48:51 -07:00
ChangeLog.2 Prefer HTTPS to FTP and HTTP 2017-09-16 17:48:51 -07:00
ChangeLog.3 maint: update URLs 2017-09-23 12:49:23 -07:00
configure.ac Add NetBSD /bin/sh to the -n whitelist. 2020-08-26 15:08:26 -04:00
COPYING Update links in COPYING, COPYINGv3, and COPYING.EXCEPTION. 2020-07-10 16:43:22 -04:00
COPYING.EXCEPTION Update links in COPYING, COPYINGv3, and COPYING.EXCEPTION. 2020-07-10 16:43:22 -04:00
COPYINGv3 Update links in COPYING, COPYINGv3, and COPYING.EXCEPTION. 2020-07-10 16:43:22 -04:00
GNUmakefile Partially revert e54e3f90: restore use of $(MAKE) in error message. 2020-08-04 08:46:59 -04:00
HACKING Remove obsolete instructions from HACKING. 2020-12-08 11:29:05 -05:00
maint.mk sc_error_message_uppercase: allow fully uppercased words 2020-11-30 11:45:25 -05:00
Makefile.am Generate manpages directly from source code. 2020-08-21 16:23:32 -04:00
NEWS maint: add outline for future NEWS (release branch). 2020-12-08 21:47:13 -05:00
README maint: make update-copyright 2020-01-01 11:45:50 -08:00
README-alpha maint: make update-copyright 2020-01-01 11:45:50 -08:00
README-hacking make fetch and update savannah gitweb urls to cgit. 2020-11-30 11:45:24 -05:00
THANKS maint: make update-copyright 2020-01-01 11:45:50 -08:00
TODO * TODO: Add -Werror support. 2020-08-06 12:28:40 -07:00

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