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 E3551385B19B; Fri, 25 Nov 2022 09:32:37 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E3551385B19B
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1669368757;
	bh=kfP0vYP58G5KSNCzvtuLAjY5/yPTXowHbOwEiuaoQpg=;
	h=From:To:Subject:Date:From;
	b=ZFlnnTR9I++5k26ODMt75UiJKIcpHF67BKb3EeEwM+FfKq5b40Q4AE9Uyys+3SIQF
	 e1bb00jNCvnvY0q1LpEG6KCYyf4m3lnTLFxW6hc0K8FtM+kZt+qb6VMQm/xw2C84ST
	 VB2yp7L+kdCINEalQ0zFTnX6kqDlWvfNPoGtABg4=
From: "shaohua.li at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug sanitizer/107866] New: gcc trunk's UBSan  misses a
 Nll-pointer-dereference at -O3.
Date: Fri, 25 Nov 2022 09:32:37 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: sanitizer
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: shaohua.li at inf dot ethz.ch
X-Bugzilla-Status: UNCONFIRMED
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: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter cc target_milestone
Message-ID: <bug-107866-4@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
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107866

            Bug ID: 107866
           Summary: gcc trunk's UBSan  misses a Nll-pointer-dereference at
                    -O3.
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: shaohua.li at inf dot ethz.ch
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxi=
n at gcc dot gnu.org
  Target Milestone: ---

For the following code, `gcc-trunk -O3 -fsanitize=3Dundefined` misses the
NULL-pointer-dereference, while `gcc-trunk -Ox -fsanitize=3Daddress` (x=3D0=
,1, 2,
s) can detect it.

gcc-12 has the same issue.
gcc-11 can detect the bug at all optimization levels.
clang can also detect it at all optimization levels.

Compiler explorer: https://godbolt.org/z/WhrzP6zdf

% cat a.c
int *a;
void main() {
  for (;;) {
    a =3D 0;
    if (*a)
      break;
  }
}
%
% gcc-tk -O3 -fsanitize=3Dundefined -fno-sanitize-recover=3Dall a.c &&./a.o=
ut
Segmentation fault
% gcc-tk -O2 -fsanitize=3Dundefined -fno-sanitize-recover=3Dall a.c &&./a.o=
ut
a.c:5:9: runtime error: load of null pointer of type 'int'
%=