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Subject: [Bug libstdc++/105730] [12 Regression] Issue with commit - Allow
 std::condition_variable waits to be cancelled
Date: Wed, 18 Jan 2023 15:14:56 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105730

--- Comment #15 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:937b0f05910bd814459ba9af0972041514274cd7

commit r12-9051-g937b0f05910bd814459ba9af0972041514274cd7
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Dec 22 09:56:47 2022 +0000

    libstdc++: Avoid recursion in __nothrow_wait_cv::wait [PR105730]

    The commit r12-5877-g9e18a25331fa25 removed the incorrect
    noexcept-specifier from std::condition_variable::wait and gave the new
    symbol version @@GLIBCXX_3.4.30. It also redefined the original symbol
    std::condition_variable::wait(unique_lock<mutex>&)@GLIBCXX_3.4.11 as an
    alias for a new symbol, __gnu_cxx::__nothrow_wait_cv::wait, which still
    has the incorrect noexcept guarantee. That __nothrow_wait_cv::wait is
    just a wrapper around the real condition_variable::wait which adds
    noexcept and so terminates on a __forced_unwind exception.

    This doesn't work on uclibc, possibly due to a dynamic linker bug. When
    __nothrow_wait_cv::wait calls the condition_variable::wait function it
    binds to the alias symbol, which means it just calls itself recursively
    until the stack overflows.

    This change avoids the possibility of a recursive call by changing the
    __nothrow_wait_cv::wait function so that instead of calling
    condition_variable::wait it re-implements it. This requires accessing
    the private _M_cond member of condition_variable, so we need to use the
    trick of instantiating a template with the member-pointer of the private
    member.

    libstdc++-v3/ChangeLog:

            PR libstdc++/105730
            * src/c++11/compatibility-condvar.cc (__nothrow_wait_cv::wait):
            Access private data member of base class and call its wait
            member.

    (cherry picked from commit ee4af2ed0b7322884ec4ff537564683c3749b813)=