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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libstdc++/99277] C++2a synchronisation is inefficient in GCC 11
 and can't be fixed later
Date: Fri, 26 Feb 2021 12:52:37 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99277

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[11 Regression] C++2a       |C++2a synchronisation is
                   |synchronisation is          |inefficient in GCC 11 and
                   |inefficient in GCC 11 and   |can't be fixed later
                   |can't be fixed later        |

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I already replied on the mailing list. These are inline specifically so we
don't tie ourselves to symbols exported from the DSO before the features are
stable.

They aren't going to be considered stable for GCC 11 so your suggestion is =
to
disable everything, get no usage experience to help improve it, then at some
point re-enable it when it's no more mature than it is now. I don't see how
that helps anything.

We've done things this way for years. When C++20 support is no longer
experimental is when the ABI will be fixed.=