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From: "w at 1wt dot eu" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c/98503] [11 regression] -Warray-bounds false positive with
 global variables at -O2 since r11-3306-g3f9a497d1b0dd9da
Date: Tue, 05 Jan 2021 11:34:45 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98503

--- Comment #9 from Willy Tarreau <w at 1wt dot eu> ---
Hi Richard,

indeed, the &curr->list =3D=3D &head is the test for end of list that preve=
nts any
bad access from happening.

I know that usually the right way to do this is by using a list element, but
sometimes it requires placing casts all over the code, or container_of() and
friends in every single call, which is way more error-prone. Writing state
machines with different input types in general doesn't result in reliable
long-term code. It turns out that in the code affected by this there were o=
nly
two call places that I could tear a little bit to use the list instead (and=
 an
alias pointer, which I hate keeping) but I'm not extremely happy with this
workaround.

I'm well aware that there can be aliasing issues while doing this, which is
also why I tested with -fno-strict-aliasing and saw the warninig remain, wh=
ich
I'd argue is definitely not appropriate in this case.

I really think that this one is border-line. Not useless at all, but should
only trigger at a higher level so that users don't have to get rid of
-Warray-bounds just because of it. The linux kernel already had to disable =
it
for other reasons and that's really sad in my opinion, which is why I'm try=
ing
hard to keep it.

Thanks,
Willy=