From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 425213850419; Mon, 8 Mar 2021 18:23:35 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 425213850419 From: "msebor at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug sanitizer/99418] sanitizer checks for accessing multidimentional VLA-array Date: Mon, 08 Mar 2021 18:23:35 +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: 10.2.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: msebor at gcc dot gnu.org X-Bugzilla-Status: WAITING 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: cc 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: Mon, 08 Mar 2021 18:23:35 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99418 Martin Sebor changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |msebor at gcc dot gnu.org --- Comment #5 from Martin Sebor --- The initialization of a reference binds it to the value of the initializer expression. In both examples the [value of the] initializer expression is undefined because it doesn't refer to an element of the array. One way to = see that is in a constexpr context which rejects undefined constructs with an e= rror (only with Clang; GCC doesn't reject invalid initialization of references there, see also pr70151): $ cat t.C && clang -S t.C constexpr int a[2] =3D { 1, 2 }; constexpr const int &r =3D a[2]; t.C:2:26: warning: array index 2 is past the end of the array (which contai= ns 2 elements) [-Warray-bounds] constexpr const int &r =3D a[2]; ^ ~ t.C:1:1: note: array 'a' declared here constexpr int a[2] =3D { 1, 2 }; ^ t.C:2:22: error: constexpr variable 'r' must be initialized by a constant expression constexpr const int &r =3D a[2]; ^ ~~~~ t.C:2:22: note: dereferenced pointer past the end of subobject of 'a' is no= t a constant expression t.C:1:15: note: declared here constexpr int a[2] =3D { 1, 2 }; ^ 1 warning and 1 error generated.=