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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/105689] Bogus `-Wstringop-overflow=` after accessing field, then containing struct (wrong "region size")
Date: Mon, 23 May 2022 20:27:05 +0000	[thread overview]
Message-ID: <bug-105689-4-mfgx232Nhb@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-105689-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105689

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
It is because of CSE.  The warning sees this IL:

  _1 = &me_3(D)->sub.field1;
  access_1 (_1);
  access_2 (_1);

and so it warns for the second call because the size of me->sub.field1 passed
to it is smaller than struct subobject.  The attribute access on access_2() is
what tells it to use the size of struct subobject.

The CSE substitution causes false positives in other contexts besides calls to
functions with attribute access.  IIRC, one of the ideas for dealing with this
we discussed was to have CSE use the largest subobject instead whatever it
comes across first.

  parent reply	other threads:[~2022-05-23 20:27 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-22 11:30 [Bug c/105689] New: " sagebar at web dot de
2022-05-23  7:30 ` [Bug c/105689] " rguenth at gcc dot gnu.org
2022-05-23 20:27 ` msebor at gcc dot gnu.org [this message]
2023-05-17 20:56 ` [Bug tree-optimization/105689] " pinskia at gcc dot gnu.org
2023-05-17 21:00 ` pinskia at gcc dot gnu.org

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