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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug other/97309] Improve documentation of -fallow-store-data-races
Date: Thu, 12 May 2022 08:58:22 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97309

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #4)
> If all accesses to a variable use atomic ops, does that mean it's immune
> from the unsafe optimizations enabled by this flag? If no, that makes -Of=
ast
> unusable in MT code. If yes, good, but why is the flag needed? If there a=
re
> non-atomic accesses to a variable, we can already assume it's not
> concurrently accessed, because any such potentially concurrent conflicting
> action would already be a data race and UB. If we already have data races
> with UB, can't we just introduce more? Is this flag saying "allow the
> compiler to make existing UB even worse"? If not, what is it saying?

Or maybe this flag is relevant for languages that don't use the C and C++
memory models, where the rules are different?=