Re: [PATCH][_GLIBCXX_INLINE_VERSION] Fix <format> friend declarations

[Jonathan Wakely <jwakely@redhat.com>]

On Wed, 23 Aug 2023 at 18:35, François Dumont via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> Hi
>
> The few tests that are failing in versioned namespace mode are due to
> those friend declarations.
>
> This is a fix proposal even if I considered 2 other options:
>
> 1. Make __format::_Arg_store a struct and so do not bother with friend
> declarations.
>
> 2. Consider it as a compiler bug and do nothing. In this case I think we
> might still need this patch to avoid a non-working format library in
> versioned namespace mode in gcc 14 if compiler bug is not fixed.

It definitely is a compiler bug, this is PR c++/59256.

Please add a comment to the new macro definition, so we remember to
remove it when it's not needed:


#if _GLIBCXX_INLINE_VERSION
// Needed because of PR c++/59526
# define _GLIBCXX_STD_V std::__8
#else
# define _GLIBCXX_STD_V std
#endif


OK with that change, thanks.




>
> I can also define _GLIBCXX_STD_V at <format> level to limit impact.
>
>      libstdc++: [_GLIBCXX_INLINE_VERSION] Fix <format> friend declarations
>
>      GCC do not consider the inline namespace in friend declarations. We
> need
>      to explicit this namespace.
>
>      libstdc++-v3/ChangeLog:
>
>              * include/bits/c++config (_GLIBCXX_STD_V): New macro giving
> current
>              std namespace with optionally the version namespace.
>              * include/std/format (std::__format::_Arg_store): Use
> latter on friend
>              declarations.
>
> Tested under versioned mode.
>
> Ok to commit ?
>
> François