libstdc++: Make std::variant work with Clang in C++20 mode [PR103891]
authorJonathan Wakely <jwakely@redhat.com>
Mon, 10 Jan 2022 17:28:19 +0000 (17:28 +0000)
committerJonathan Wakely <jwakely@redhat.com>
Tue, 11 Jan 2022 13:22:35 +0000 (13:22 +0000)
commit5b417b35824fb5c15e3ee958cb86436b3409ebea
tree200cfb1337a68b8be3cc6c976272aece4f0ec425
parent11d3e8f4364b05e2746689c6d0f573594f6ddb74
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.
libstdc++-v3/include/bits/c++config
libstdc++-v3/include/std/variant
libstdc++-v3/include/std/version