[PATCH] libstdc++: Fix UB in atomic_ref/wait_notify.cc [PR101761]

[Jonathan Wakely]

On Thu, 16 Sep 2021, 23:24 Thomas Rodgers, <rodgert@appliantology.com>
wrote:

> From: Thomas Rodgers <rodgert@twrodgers.com>
>
> Remove UB in atomic_ref/wait_notify test.
>
> Signed-off-by: Thomas Rodgers <trodgers@redhat.com>
>
> libstdc++-v3/ChangeLog:
>
>         PR libstdc++/101761
>         * testsuite/29_atomics/atomic_ref/wait_notify.cc (test): Use
>         va and vb as arguments to wait/notify, remove unused bb local.
>
> Tested x86_64-pc-linux-gnu, committed to master.
> Ok to backport to releases/gcc-11?
>


Yes, ok for 11, thanks.



> ---
>  .../testsuite/29_atomics/atomic_ref/wait_notify.cc         | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/libstdc++-v3/testsuite/29_atomics/atomic_ref/wait_notify.cc
> b/libstdc++-v3/testsuite/29_atomics/atomic_ref/wait_notify.cc
> index b75e27617f7..b41d1ac0bb7 100644
> --- a/libstdc++-v3/testsuite/29_atomics/atomic_ref/wait_notify.cc
> +++ b/libstdc++-v3/testsuite/29_atomics/atomic_ref/wait_notify.cc
> @@ -33,15 +33,14 @@ template<typename S>
>      if constexpr (std::atomic_ref<S>::is_always_lock_free)
>      {
>        S aa{ va };
> -      S bb{ vb };
>        std::atomic_ref<S> a{ aa };
> -      a.wait(bb);
> +      a.wait(vb);
>        std::thread t([&]
>          {
> -         a.store(bb);
> +         a.store(vb);
>           a.notify_one();
>          });
> -      a.wait(aa);
> +      a.wait(va);
>        t.join();
>      }
>    }
> --
> 2.31.1
>
>