From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id E278E3858423; Thu, 9 Feb 2023 20:12:26 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E278E3858423 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1675973546; bh=VqSx29eto6fLFokGkfAjkSmZZJyf2DHTvx77oFfKFzo=; h=From:To:Subject:Date:In-Reply-To:References:From; b=bxZSazYQw6daApy/Zo0RYOkKO9KeSpfc0tOjEuEFn4GeCbxL2m3iQntS2Ig06+fH3 Olfd4UIWZHdjQPjCRn05O6bOMIt/ph+6RkGoeuj996UUXcgK+n70adCJi36bMOx75v MEmcCQhs70FzJp8PVTVjohGxfTQqHaJXAA4pVTm0= From: "jakub at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug c/108718] [10/11/12/13 Regression] csmith: possible bad code with -O2 Date: Thu, 09 Feb 2023 20:12:26 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c X-Bugzilla-Version: 13.0 X-Bugzilla-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: jakub at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 10.5 X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 List-Id: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108718 --- Comment #5 from Jakub Jelinek --- (In reply to David Binderman from comment #4) > (In reply to Andrew Pinski from comment #3) > > This also changes with -fno-strict-aliasing ... >=20 > So does that mean that csmith is producing C code with UB and so > this bug isn't valid ? Not necessarily. If something misbehaves with -O2 and behaves as expected = with -O2 -fno-strict-aliasing, then it is usually a good sign that there is or m= ight be an aliasing violation, but it isn't a proof that there is one. Only detailed analysis of the code or e.g. the latter only focused on what exact= ly changes with the bisection point can reveal if it is or isn't valid.=