From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 20114 invoked by alias); 16 Oct 2014 17:10:56 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org Received: (qmail 20042 invoked by uid 48); 16 Oct 2014 17:10:52 -0000 From: "jakub at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug sanitizer/63564] -fsanitize=address obscures access to free memory Date: Thu, 16 Oct 2014 17:10:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: sanitizer X-Bugzilla-Version: 5.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: jakub at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED 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: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2014-10/txt/msg01297.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63564 --- Comment #1 from Jakub Jelinek --- You would need glibc compiled with -fsanitize=address (unless the write is done in assembly) to detect that. And, the reason that glibc malloc reports the problem is that it performs some cheap checks, in particular if you happen to overwrite glibc malloc's internal data structures, it will sometimes be able to cheaply detect that and report. asan malloc doesn't have anything like that. Expecting that -fsanitize=address will reveal all issues in your code is unrealistic.