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 564AC3858D35; Thu,  6 Aug 2020 00:07:47 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 564AC3858D35
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
 s=default; t=1596672467;
 bh=JPdmh31k043bnBklh0GaddDFezIpULyZON75exigPrM=;
 h=From:To:Subject:Date:In-Reply-To:References:From;
 b=XYjlzHIip/c8cb6Ok4tQ3QwKa82rmDUD2xoeQev9+Eti2A6gAJHFhJs3cyc34ppQb
 hRvxcox3qbAoIuGwxAi0nPy+YknA0/YyupIKNpQpeJJVi8RB1ErIRxGjrg/0NZfJ0P
 hyry5id+i9ic07r3Kh1rtLyFAXFS/zqxkuI1KaDc=
From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/96468] Warn when an empty while loop could have been a do-while
Date: Thu, 06 Aug 2020 00:07:47 +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: 10.2.0
X-Bugzilla-Keywords: diagnostic
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: msebor at gcc dot gnu.org
X-Bugzilla-Status: NEW
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: component
Message-ID: <bug-96468-4-cyk66Cq4Un@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-96468-4@http.gcc.gnu.org/bugzilla/>
References: <bug-96468-4@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: Thu, 06 Aug 2020 00:07:47 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96468

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|tree-optimization           |c

--- Comment #6 from Martin Sebor <msebor at gcc dot gnu.org> ---
Oh.  So you're just looking for a simple lexical check to see if a while
statement is preceded by a block { } and a warning if it is and (presumably)
isn't the result of macro expansion.  E.g., issue a warning here:

  void f (void)
  {
    { debug ("in f ()"); }
    while (!signaled);   // warn
  }

but not here (:

  void f (void)
  {
    DEBUG   // expands to { debug (...); }
    while (!signaled);   // don't warn
  }

That should be simpler and doable in the front end (so back to C for compon=
ent)
but also seems considerably less useful to me as well as more prone to nois=
e.=20

Front end isn't really my area so I don't expect to work on this but a coup=
le
of questions occur to me: should blank lines between the closing curly or t=
he
while have any effect on the warnig?  If yes as I would expect it starts to
feel like it's in the same area as -Wmisleading-indentation.  What about ot=
her
iteration statements -- should those be considered as well?

  while (condition);   // warning? (spurious semicolon)
  { }

  for (...; condition; ...);   // ditto
  { }=