[Bug libstdc++/102270] std::tuple<>::swap missing constexpr specifier

[hewillk at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102270

--- Comment #4 from 康桓瑋 <hewillk at gmail dot com> ---
(In reply to CVS Commits from comment #3)
> The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>:
> 
> https://gcc.gnu.org/g:734b2c2eedca50d966e22540fc136158c3633393
> 
> commit r12-3592-g734b2c2eedca50d966e22540fc136158c3633393
> Author: Jonathan Wakely <jwak...@redhat.com>
> Date:   Wed Sep 15 21:53:35 2021 +0100
> 
>     libstdc++: Add missing 'constexpr' to std::tuple [PR102270]
>     
>     Signed-off-by: Jonathan Wakely <jwak...@redhat.com>
>     
>     libstdc++-v3/ChangeLog:
>     
>             PR libstdc++/102270
>             * include/std/tuple (_Head_base, _Tuple_impl): Add
>             _GLIBCXX20_CONSTEXPR to allocator-extended constructors.
>             (tuple<>::swap(tuple&)): Add _GLIBCXX20_CONSTEXPR.
>             * testsuite/20_util/tuple/cons/102270.C: New test.

tuple#L332:

template<typename _Alloc>
  _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
            const _Head& __head, const _Tail&... __tail)
  : _Inherited(__tag, __a, __tail...),
  _Base(__use_alloc<_Head, _Alloc, _Head>(__a), __head)
  { }