From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 3C4C1385840C; Mon, 17 Jan 2022 21:52:53 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 3C4C1385840C
From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/104069] -Werror=use-after-free false positive
 on elfutils-0.186
Date: Mon, 17 Jan 2022 21:52:53 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: diagnostic
X-Bugzilla-Severity: normal
X-Bugzilla-Who: msebor at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: msebor at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-104069-4-Snpqceyg5g@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-104069-4@http.gcc.gnu.org/bugzilla/>
References: <bug-104069-4@http.gcc.gnu.org/bugzilla/>
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 <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Mon, 17 Jan 2022 21:52:53 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104069

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
Actually, this is already supposed to be handled but the code is not effect=
ive
due to a typo.  This fixes it:

diff --git a/gcc/gimple-ssa-warn-access.cc b/gcc/gimple-ssa-warn-access.cc
index f639807a78a..f9508a1d211 100644
--- a/gcc/gimple-ssa-warn-access.cc
+++ b/gcc/gimple-ssa-warn-access.cc
@@ -4082,7 +4082,9 @@ pointers_related_p (gimple *stmt, tree p, tree q,
pointer_query &qry)
   access_ref pref, qref;
   if (!qry.get_ref (p, stmt, &pref, 0)
       || !qry.get_ref (q, stmt, &qref, 0))
-    return true;
+    /* GET_REF() only rarely fails.  When it does, it's likely because
+       it involves a self-referential PHI.  Return a conservative result. =
 */
+    return false;

   return pref.ref =3D=3D qref.ref;
 }=