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 2E74F3857C6D; Wed,  6 Jul 2022 17:53:31 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2E74F3857C6D
From: "qinzhao at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/101836] __builtin_object_size(P->M, 1) where M is an
 array and the last member of a struct fails
Date: Wed, 06 Jul 2022 17:53:30 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: qinzhao at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: qinzhao at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-101836-4-n2BxhBXZrw@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-101836-4@http.gcc.gnu.org/bugzilla/>
References: <bug-101836-4@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: Wed, 06 Jul 2022 17:53:31 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101836

--- Comment #35 from qinzhao at gcc dot gnu.org ---
(In reply to James Y Knight from comment #33)

>=20
> I don't understand what the -Wstrict-flex-arrays warning and its multiple
> levels is proposed to actually do.
>=20
> Is it supposed to warn on the structs that change behavior in the
> corresponding -fstrict-flex-array=3DLEVEL? But that would mean
> -Wstrict-flex-arrays=3D1 would warn on any array at the end of a struct w=
hich
> has a size other than 0 or 1. That's clearly not going to be actually
> practical...so perhaps you had something else in mind?


I think that -Wstrict-flex-arrays will need to be cooperated with
-fstrict-flex-arrays=3DN, i.e, only when -fstrict-flex-arrays=3DN is presen=
ting,
-Wstrict-flex-arrays will be valid and report the warnings when see a [0], =
or
[1], or any trailing array based on N:

when -fstrict-flex-arrays
=3D0, -Wstrict-flex-arrays will NOT issue any warnings;
=3D1, -Wstrict-flex-arrays will issue warnings when an array ref's index is
larger than the upper bounds of a trailing array that is a regular trailing
array;
=3D2, -Wstrict-flex-arrays will issue warnings when an array ref's index is
larger than the upper bounds of a trailing array that is a regular trailing
array or [1];
=3D3, -Wstrict-flex-arrays will issue warnings when an array ref's index is
larger than the upper bounds of a trailing array that is a regular trailing
array or [1], or [0].

let me know if you have any comment and suggestion on this.=