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From: "dcb314 at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/112550] Difference in output from -O0 to -01 ?
Date: Wed, 15 Nov 2023 16:59:54 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112550

--- Comment #2 from David Binderman <dcb314 at hotmail dot com> ---
(In reply to Sam James from comment #1)
> Not sure if I'm misunderstanding you, but it's not trivial to go from -O0
> and -O1 and it's "normal" to have a difference in output in either the ca=
se
> of: a) UB, or b) a compiler bug (miscompilation).

The source code I provided is produced by csmith and then preprocessed.

I tried the upstream unpreprocessed source code on clang -O0 and gcc -O0
and they agreed on the output, so it looked to me like csmith was working o=
k.

Only when I changed over from gcc -O0 to gcc -O1 did I see a difference.=