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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/114872] [13/14/15 Regression] Miscompilation
 with -O2 after commit r13-8037
Date: Wed, 08 May 2024 19:58:26 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114872

--- Comment #28 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Dmitrii Pasechnik from comment #26)
> We have megabytes of code calling libraries where setjmp/longjmp is used,
> in github.com/sagemath/sage/ (most of it in Cython).
>=20
> It looks like a huge hassle to put volatiles there.=20
> Looks like we would need ways to disable particular optimisations which l=
ead
> to these sorts of errors:-(

You mean turn off all optimizations then?  -O0.
Even that doesn't guarantee it will work if some such variables are declared
with register keyword.

It isn't just POSIX which says this, e.g. C99 also says:
"All accessible objects have values, and all other components of the abstra=
ct
machine
have state, as of the time the longjmp function was called, except that the
values of
objects of automatic storage duration that are local to the function contai=
ning
the
invocation of the corresponding setjmp macro that do not have
volatile-qualified type
and have been changed between the setjmp invocation and longjmp call are
indeterminate."
C89 said pretty much the same.=