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Subject: |
AM_PROG_CC_C_O is disabled by gnulib std-gnu11.m4 |
Date: |
Wed, 2 May 2018 15:56:01 -0700 |
User-agent: |
Mutt/1.9.4 (2018-02-28) |
Hi,
In GNU Octave, we are embracing a lot of C++11, and so we are using the
gnulib std-gnu11.m4 drop-in to ensure that the compiler conforms to the
latest standards. I think several other GNU projects also use this file.
The std-gnu11.m4 file defines AC_PROG_CC and AC_PROG_CXX replacements,
which I think are backported from Autoconf git.
In a trivial project, for example
AC_INIT([test], [0])
AM_INIT_AUTOMAKE([1.14 foreign])
AC_PROG_CC
AC_CONFIG_FILES([Makefile])
AC_OUTPUT
the AM_PROG_CC_C_O feature test is automatically called, as expected and
described in the Automake 1.14 NEWS.
With std-gnu11.m4 added to this project, however, the AM_PROG_CC_C_O
macro is no longer called, either automatically or manually. The
intention of Automake to ensure that this test is always done is
defeated simply by including this file.
If a call to the real macro
_AM_PROG_CC_C_O
is added after AC_PROG_CC, then the feature test is restored.
I know enough m4 to get by, but I suspect this has to do with the order
of inclusion, and that Automake redefines AC_PROG_CC to call its own
_AM_PROG_CC_C_O, which is later clobbered by the inclusion of
std-gnu11.m4.
Is there anything Automake can do to ensure that AM_PROG_CC_C_O is
called even if AC_PROG_CC is redefined locally?
Even if you judge this not to be an Automake bug, I wanted to bring this
to your attention, since the std-gnu11.m4 file is the recommended way to
rely on modern language standards support at the moment.
Thanks,
--
mike
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Subject: |
Re: bug#31347: AM_PROG_CC_C_O is disabled by gnulib std-gnu11.m4 |
Date: |
Fri, 10 Dec 2021 02:38:19 -0500 |
On 03 May 2018 10:11, Jamal Natour wrote:
> As a user of C++11 and C++14, I use the ax_cxx_compile_stdcxx variants,
> these have seemed to work on the various combinations of
> platforms/compilers I've used.
>
> https://github.com/jamal-fuma/fuma_m4/blob/master/ax_cxx_compile_stdcxx.m4
> https://github.com/jamal-fuma/fuma_m4/blob/master/ax_cxx_compile_stdcxx_14.m4
>
> Perhaps these will offer a workaround until such time as you can solve
> the issue.
yeah, i'm kind of inclined to say use macros from the autoconf archive instead:
https://www.gnu.org/software/autoconf-archive/
that said, the latest autoconf release defaults to C11 if it can find it, so
maybe the issue in general is moot ?
you might have found a real bug, but i'm not sure how much effort we want to
put into having internal autoconf macros redefined.
-mike
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