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 8476A385EC54; Mon, 16 Aug 2021 10:22:52 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 8476A385EC54
From: "tschwinge at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/101862] [C, C++] Potential '?:' diagnostic for
 always-true expressions in boolean context
Date: Mon, 16 Aug 2021 10:22:52 +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: diagnostic
X-Bugzilla-Severity: normal
X-Bugzilla-Who: tschwinge 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: 
Message-ID: <bug-101862-4-fBuk1mhzPi@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-101862-4@http.gcc.gnu.org/bugzilla/>
References: <bug-101862-4@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: Mon, 16 Aug 2021 10:22:52 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101862

--- Comment #3 from Thomas Schwinge <tschwinge at gcc dot gnu.org> ---
Thanks for your comments!


(In reply to Andrew Macleod from comment #1)
> I'm not sure exactly what you want to do.

Neither am I!  ;-) (Well, I do know "what", but not yet "how".)

> The EVRP pass recognizes [...]

> This seems to be too late to determine that a warning might be appropriat=
e..
> and I'm not sure how you would figure that out from this IL.
>=20
> We have to go way back before gimple before we see the conditional
> expression.

> The range machinery knows what you want to know, but IM not sure how you
> could use it. Its only available once we go into SSA.

Idea: preserve the original front end AST (or whatever is appropriate), for
"potential diagnostics" ("delayed diagnostics"?), and then (re-)evaluate on=
ce
we have VR information (and whatever else is necessary).


> we usually rejoice when we can fold asserts away :-)

A classic case of tuning for code generation vs. diagnostics.  ;-)=