[PATCH] Fix inline versioned namespace bootstrap

[Jonathan Wakely]

On Sat, 28 Aug 2021 at 13:40, François Dumont <frs.dumont@gmail.com> wrote:
>
> On 28/08/21 12:49 pm, Jonathan Wakely wrote:
> > On Sat, 28 Aug 2021 at 10:26, Jonathan Wakely <jwakely@redhat.com> wrote:
> >> On Fri, 27 Aug 2021 at 22:17, Jonathan Wakely <jwakely@redhat.com> wrote:
> >>> On Fri, 27 Aug 2021 at 21:58, François Dumont via Libstdc++
> >>> <libstdc++@gcc.gnu.org> wrote:
> >>>> Since std::allocator<void> is not specialized anymore in
> >>>> _GLIBCXX_INLINE_VERSION mode _ExtPtr_allocator<void> specialization do
> >>>> not compile
> >>>>
> >>>> because std::allocator<void> is incomplete.
> >>> That doesn't look right ... it should be complete. This suggests there
> >>> is a deeper problem, which I'll look into.
> >> This is the correct fix:
> >>
> >> --- a/libstdc++-v3/include/bits/memoryfwd.h
> >> +++ b/libstdc++-v3/include/bits/memoryfwd.h
> >> @@ -63,8 +63,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >>    template<typename>
> >>      class allocator;
> >>
> >> +#if ! _GLIBCXX_INLINE_VERSION
> >>    template<>
> >>      class allocator<void>;
> >> +#endif
> >>
> >> #if __cplusplus >= 201103L
> >>    /// Declare uses_allocator so it can be specialized in `<queue>` etc.
> >
> > Actually, the allocator<void> specialization is still needed for
> > pre-C++20 with the versioned namespace, and that means there's the
> > same trivial default ctor ABI concern for the versioned namespace. I'm
> > testing a fix now, but it might not be committed until I'm back at
> > work on Tuesday.
> >
> Ok, there's no rush.

I've pushed the fix now.

>
> Note that I noticed that because I am working on PR 83077 to allow sso
> string in versioned namespace.
>
> My plan is to make the sso string the only std::string implementation in
> versioned namespace.

Great, thanks.

>
> Now that I saw your RFC about dropping C++98 support for versioned
> namespace I think my approach fall into this. But I also think that this
> RFC will be approved so it should be fine unless you have another concern.
>
> François
>