Re: Request to revert the C version change

[Zack Weinberg <zackw@panix.com>]

On Wed, Dec 16, 2020 at 2:02 PM Zack Weinberg <zackw@panix.com> wrote:
> On Wed, Dec 16, 2020 at 1:52 PM Ross Burton <ross@burtonini.com> wrote:
> > | checking for gcc  option to enable C11 features... none needed
> > | ../bison-3.7.4/configure: line 6187: syntax error near unexpected
> > token `ac_cv_prog_cc_stdc=$ac_cv_prog_cc_c89'
> > | ../bison-3.7.4/configure: line 6187: `
> > ac_cv_prog_cc_stdc=$ac_cv_prog_cc_c89'
> >
> > gettext failed in the same manner.
> >
> > I can bisect and identify where it broke tomorrow.
>
> Thanks.  This is definitely not a failure I saw in my testing, but it
> smells like another typo in the shell code, so hopefully not hard to
> fix.

The problem appears to be that gnulib's std-gnu11.m4 replaces *most*
of the definition of AC_PROG_CC, in a way that conflicts with the
refactor.  I'm looking for a way to avoid the conflict within autoconf
proper, but a workaround is to apply this patch to std-gnu11.m4:

$ diff -u m4/std-gnu11.m4{~,}
--- m4/std-gnu11.m4~    2020-08-30 11:27:01.000000000 -0400
+++ m4/std-gnu11.m4    2020-12-20 09:43:13.001477099 -0500
@@ -27,6 +27,8 @@
 # François Pinard, Karl Berry, Richard Pixley, Ian Lance Taylor,
 # Roland McGrath, Noah Friedman, david d zuhn, and many others.

+m4_version_prereq([2.70], [], [
+

 # AC_PROG_CC([COMPILER ...])
 # --------------------------
@@ -822,3 +824,5 @@
 dnl with extended modes being tried first.
 [[-std=gnu++11 -std=c++11 -std=gnu++0x -std=c++0x
-qlanglvl=extended0x -AA]], [$1], [$2])[]dnl
 ])# _AC_PROG_CXX_CXX11
+
+])# m4_version_prereq

I recommend this patch be applied in Gnulib proper.  It may be wise to
go through all of gnulib's m4 files and see if any others need the
same treatment.  (Any m4 file that backports code from the development
series leading up to 2.70 is a candidate.)

zw