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From: "christian.prochaska@genode-labs.com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/104288] [11/12 Regression] EVRP null pointer
 check removal for strcmp (and maybe others) is not flow senative
Date: Sun, 09 Apr 2023 07:07:32 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 11.2.1
X-Bugzilla-Keywords: wrong-code
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X-Bugzilla-Who: christian.prochaska@genode-labs.com
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X-Bugzilla-Resolution: FIXED
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104288

--- Comment #16 from Christian Prochaska <christian.prochaska@genode-labs.c=
om> ---
(In reply to Andrew Pinski from comment #14)
>=20
> There was a deferencing of myself before:
> Nova::Utcb &utcb =3D *(Nova::Utcb *)myself->utcb();

I see. The 'Thread::utcb()' function handles the null pointer case internal=
ly
with a 'this =3D=3D 0' check and a local '-fno-delete-null-pointer-checks'
attribute:

https://github.com/genodelabs/genode/blob/a84af9a9606450471b8038a35f9b55057=
efa0850/repos/base-nova/src/lib/base/stack.cc#L110

So, the elimination of the 'myself' null pointer check is basically a resul=
t of
undefined behavior with the 'Thread::utcb()' function?=