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 AE6123950402; Fri, 29 Jan 2021 17:43:52 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org AE6123950402
From: "ppalka at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/82877] negative array index accepted in a pointer
 difference expression in constexpr context
Date: Fri, 29 Jan 2021 17:43:52 +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: 8.0
X-Bugzilla-Keywords: accepts-invalid
X-Bugzilla-Severity: normal
X-Bugzilla-Who: ppalka at gcc dot gnu.org
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: cc
Message-ID: <bug-82877-4-SwF9KBNw5e@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-82877-4@http.gcc.gnu.org/bugzilla/>
References: <bug-82877-4@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: Fri, 29 Jan 2021 17:43:52 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D82877

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ppalka at gcc dot gnu.org

--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Looks we correctly reject the testcase starting with GCC 9.1 (r9-6136):

<source>:9:21:   in 'constexpr' expansion of 'f()'
<source>:9:22: error: array subscript value '-1' is outside the bounds of a=
rray
type 'int [1]'
    9 | constexpr int i =3D f ();
      |                      ^

Starting with GCC 10.1, the diagnostic also points to the correct line:

source>:9:21:   in 'constexpr' expansion of 'f()'
<source>:6:27: error: array subscript value '-1' is outside the bounds of a=
rray
type 'int [1]'
    6 |   return &s.a[0] - &s.a[-1];   // undefined, should be rejected
      |                     ~~~~~~^=