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Subject: [Bug c++/102177] Implement C++17 P0418R2
Date: Thu, 21 Apr 2022 15:33:56 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102177

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:fef3d31bd35f53cbcacaec63b279d38c38b78abe

commit r11-9926-gfef3d31bd35f53cbcacaec63b279d38c38b78abe
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Sep 2 15:29:22 2021 +0100

    libstdc++: Remove "no stronger" assertion in compare exchange [PR102177]

    P0418R2 removed some preconditions from std::atomic::compare_exchange_*
    but we still enforce them via __glibcxx_assert. This removes those
    assertions.

    Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

    libstdc++-v3/ChangeLog:

            PR c++/102177
            * include/bits/atomic_base.h (__is_valid_cmpexch_failure_order):
            New function to check if a memory order is valid for the failure
            case of compare exchange operations.
            (__atomic_base<I>::compare_exchange_weak): Simplify assertions
            by using __is_valid_cmpexch_failure_order.
            (__atomic_base<I>::compare_exchange_strong): Likewise.
            (__atomic_base<P*>::compare_exchange_weak): Likewise.
            (__atomic_base<P*>::compare_exchange_strong): Likewise.
            (__atomic_impl::compare_exchange_weak): Add assertion.
            (__atomic_impl::compare_exchange_strong): Likewise.
            * include/std/atomic (atomic::compare_exchange_weak): Likewise.
            (atomic::compare_exchange_strong): Likewise.

    (cherry picked from commit dba1ab212292839572fda60df00965e094a11252)=