[PATCH v2] libstdc++: Add module initialization functions to the library [PR124268]

[Jonathan Wakely]

On Tue, 17 Mar 2026 at 10:13, Gerald Pfeifer <gerald@pfeifer.com> wrote:
>
> On Mon, 16 Mar 2026, Jonathan Wakely wrote:
> > This ensures that the module init functions are present in libstdc++.so
> > and libstdc++.a, so that users of the std and std.compat modules don't
> > need to manually link to std.o and/or std.compat.o in addition to
> > compiling the CMIs.
> :
> > libstdc++-v3/ChangeLog:
> >
> >       PR libstdc++/124268
> >       * config/abi/pre/gnu.ver: Export symbols.
> >       * src/Makefile.am: Add libmodulesconvenience.la to libstdc++
> >       link.
> >       * src/Makefile.in: Regenerate.
> >       * src/c++23/Makefile.am: Create libmodulesconvenience.la
> >       and populate it with std.o and std.compat.o interface units.
> >       Add clean-local target.
> >       * src/c++23/Makefile.in: Regenerate.
>
> It looks like this broke bootstrap on FreeBSD 13/amd64:
>
> libtool: link: ( cd ".libs" && rm -f "libc++23convenience.la" && ln -s "../libc++23convenience.la" "libc++23convenience.la" )
> std.cc:3799:14: error: exporting 'int feclearexcept(int)' that does not have external linkage
>  3799 |   using std::feclearexcept;
>       |              ^~~~~~~~~~~~~
> In file included from /scratch/tmp/gerald/OBJ-0317-0208/x86_64-unknown-freebsd13.5/libstdc++-v3/include/fenv.h:41,
>                  from /scratch/tmp/gerald/OBJ-0317-0208/x86_64-unknown-freebsd13.5/libstdc++-v3/include/cfenv:43,
>                  from /scratch/tmp/gerald/OBJ-0317-0208/x86_64-unknown-freebsd13.5/libstdc++-v3/include/x86_64-unknown-freebsd13.5/bits/stdc++.h:123,
>                  from std.cc:26:
> /usr/include/fenv.h:265:1: note: 'int feclearexcept(int)' declared here with internal linkage
>   265 | feclearexcept(int __excepts)
>       | ^~~~~~~~~~~~~
> std.cc:3801:14: error: exporting 'int fegetexceptflag(fexcept_t*, int)' that does not have external linkage
>  3801 |   using std::fegetexceptflag;
>       |              ^~~~~~~~~~~~~~~
> /usr/include/fenv.h:283:1: note: 'int fegetexceptflag(fexcept_t*, int)' declared here with internal linkage
>   283 | fegetexceptflag(fexcept_t *__flagp, int __excepts)
>       | ^~~~~~~~~~~~~~~
>   :
> gmake[2]: *** [Makefile:17779: all-stage1-target-libstdc++-v3] Error 2
> gmake[2]: Leaving directory '/scratch/tmp/gerald/OBJ-0317-0208'
> gmake[1]: *** [Makefile:26906: stage1-bubble] Error 2
> gmake[1]: Leaving directory '/scratch/tmp/gerald/OBJ-0317-0208'
> gmake: *** [Makefile:27243: bootstrap] Error 2
>
>
> Looking at /usr/include/fenv.h I see
>
>   #ifndef __fenv_static
>   #define __fenv_static   static
>   #endif
>
>   :
>
>   __fenv_static inline int
>   feclearexcept(int __excepts)
>   {
>   :
>   }
>
> I also found the same on a FreeBSD 15 system, so it's not just that older
> release which is going to be EOL in two months.

I'm pretty sure this is not conforming to the C standard:
https://cigix.me/c23#7.1.2.p8

This is going to be a problem for anybody trying to use the 'std'
module on FreeBSD, it seems like I'm just the first person to ever try
it :-)

We might need to use fixincludes here.