From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 3A53B385B83D; Wed, 10 Aug 2022 14:46:44 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 3A53B385B83D From: "rguenth at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/106578] spurious -Wuse-after-free=2 after conditional free() Date: Wed, 10 Aug 2022 14:46:44 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: middle-end X-Bugzilla-Version: 12.1.1 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: rguenth at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: cf_reconfirmed_on bug_status everconfirmed 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 X-BeenThere: gcc-bugs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-bugs mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 10 Aug 2022 14:46:44 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106578 Richard Biener changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2022-08-10 Status|UNCONFIRMED |NEW Ever confirmed|0 |1 --- Comment #2 from Richard Biener --- The pattern matching of the if (result =3D=3D NULL) doesn't work reliably w= ithout optimization because it goes through memory: : tmp_5 =3D buf; _1 =3D realloc (tmp_5, 10); buf =3D _1; buf.0_2 =3D buf; if (buf.0_2 =3D=3D 0B) goto ; [INV] else goto ; [INV] : free (tmp_5); : _9 =3D 0; : : return _9; using 'tmp' instead makes it properly fire. Could be fixed with extra compile-time cycles doing virtual VN like we do for early uninit analysis (note this is the late waccess pass).=