From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id E6883385801A; Sat, 27 Mar 2021 19:19:36 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E6883385801A From: "pinskia at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug c/99797] accessing uninitialized automatic variables Date: Sat, 27 Mar 2021 19:19:36 +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: 11.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: pinskia at gcc dot gnu.org X-Bugzilla-Status: RESOLVED X-Bugzilla-Resolution: WONTFIX 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: resolution bug_status 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: Sat, 27 Mar 2021 19:19:37 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99797 Andrew Pinski changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |WONTFIX Status|UNCONFIRMED |RESOLVED --- Comment #1 from Andrew Pinski --- >Ideally, I think GCC should reject code when it is clearly UB (address not= taken). It can't because it is only undefined at runtime which means if it is never invoked the undefined behavior will never been seen. GCC does warn with -Wall which should be good enough for this case: apinski@xeond:~$ ~/upstream-gcc/bin/gcc -Wall t77.c -O2 -S t77.c: In function =E2=80=98foo=E2=80=99: t77.c:9:8: warning: =E2=80=98c=E2=80=99 is used uninitialized [-Wuninitiali= zed] 9 | if (!c) | ^ >Still when taking the address of 'c' the code is not UB NO it is still undefined.=