[Bug libstdc++/103891] clang-13 fails to compile libstdc++'s std::variant<std::vector<int>>: error: attempt to use a deleted function

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103891

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:5b417b35824fb5c15e3ee958cb86436b3409ebea

commit r12-6439-g5b417b35824fb5c15e3ee958cb86436b3409ebea
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Jan 10 17:28:19 2022 +0000

    libstdc++: Make std::variant work with Clang in C++20 mode [PR103891]

    Clang has some bugs with destructors that use constraints to be
    conditionally trivial, so disable the P2231R1 constexpr changes to
    std::variant unless the compiler is GCC 12 or later.

    If/when P2493R0 gets accepted and implemented by G++ we can remove the
    __GNUC__ check and use __cpp_concepts >= 202002 instead.

    libstdc++-v3/ChangeLog:

            PR libstdc++/103891
            * include/bits/c++config
(_GLIBCXX_HAVE_COND_TRIVIAL_SPECIAL_MEMBERS):
            Define.
            * include/std/variant (__cpp_lib_variant): Only define C++20
            value when the compiler is known to support conditionally
            trivial destructors.
            * include/std/version (__cpp_lib_variant): Likewise.