From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-398117-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 29599 invoked by alias); 7 Aug 2012 15:28:05 -0000
Received: (qmail 29591 invoked by uid 22791); 7 Aug 2012 15:28:05 -0000
X-SWARE-Spam-Status: No, hits=-3.6 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00
X-Spam-Check-By: sourceware.org
Received: from localhost (HELO gcc.gnu.org) (127.0.0.1)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 07 Aug 2012 15:27:46 +0000
From: "csaba_22 at yahoo dot co.uk" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/54194] New: GCC 4.8 gives misleading suggestion about arithmetic in operand of '|'
Date: Tue, 07 Aug 2012 15:28:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Keywords:
X-Bugzilla-Severity: minor
X-Bugzilla-Who: csaba_22 at yahoo dot co.uk
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields:
Message-ID: <bug-54194-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2012-08/txt/msg00389.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54194

             Bug #: 54194
           Summary: GCC 4.8 gives misleading suggestion about arithmetic
                    in operand of '|'
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: csaba_22@yahoo.co.uk


Using gcc version 4.8.0 20120806 (experimental) (GCC),
Target: x86_64-unknown-linux-gnu

to compile the following code:

int main()
{
char in[4]={0}, out[6];
out[1] = in[1] & 0x0F | ((in[3] & 0x3C) << 2);
}

results in a misleading warning (misplaced caret):

$ g++-48 -c -Wall -Werror w.cc
w.cc: In function 'int main()':
w.cc:4:45: error: suggest parentheses around arithmetic in operand of '|'
[-Werror=parentheses]
 out[1] = in[1] & 0x0F | ((in[3] & 0x3C) << 2);
                                             ^

The problematic operand is the left operand of '|', but the caret appears to be
pointing at the right operand.

For example, clang version 3.2 (trunk 161319) gives
$ clang++ -c -Wall -Werror w.cc
w.cc:4:16: error: '&' within '|' [-Werror,-Wbitwise-op-parentheses]
out[1] = in[1] & 0x0F | ((in[3] & 0x3C) << 2);
         ~~~~~~^~~~~~ ~
w.cc:4:16: note: place parentheses around the '&' expression to silence this
warning
out[1] = in[1] & 0x0F | ((in[3] & 0x3C) << 2);
               ^
         (           )