[Bug target/125312] [16/17 Regression] x86_64-w64-mingw32: weak_ptr::lock() / shared_from_this() multi-thread stress fails

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125312

--- Comment #16 from GCC 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:1b191d0a23f3b82f6543913f8c3c2e46942af859

commit r17-552-g1b191d0a23f3b82f6543913f8c3c2e46942af859
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri May 15 10:41:33 2026 +0100

    libstdc++: Make configure check for atomics work on Windows [PR125312]

    The changes in r16-427-g86627faec10da5 do not work for native mingw-w64
    builds because the #include with a hardcoded unix-style path doesn't
    work for a native mingw-w64 compiler. This results in configure
    detecting that native mingw builds do not support atomic builtins for
    the _Atomic_word type, causing non-inline atomics to be used for
    __gnu_cxx::__exchange_and_add and __gnu_cxx::__atomic_add, which is an
    unintented ABI change (and inconsistent with mingw cross-compilers where
    the configure test passes and so enables the inline functions using
    atomic builtins).

    This attempts to solve the problem by copying the atomic_word.h header
    to the current working directory, so it can be included without using an
    absolute path.

    libstdc++-v3/ChangeLog:

            PR libstdc++/125312
            * acinclude.m4 (GLIBCXX_ENABLE_ATOMIC_BUILTINS): Copy header
            into cwd instead of including it via an absolute path.
            * configure: Regenerate.