From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-372609-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 1450 invoked by alias); 2 Nov 2011 09:37:07 -0000
Received: (qmail 1437 invoked by uid 22791); 2 Nov 2011 09:37:06 -0000
X-SWARE-Spam-Status: No, hits=-2.8 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00,TW_TM
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; Wed, 02 Nov 2011 09:36:53 +0000
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/50957] [C++0x][constexpr] complex<T> ctor drops sign of zero (sometimes)
Date: Wed, 02 Nov 2011 09:37:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields: Status Keywords Last reconfirmed Component CC Ever Confirmed Summary Known to fail
Message-ID: <bug-50957-4-mIym08VwB5@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-50957-4@http.gcc.gnu.org/bugzilla/>
References: <bug-50957-4@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: 2011-11/txt/msg00105.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50957

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |wrong-code
   Last reconfirmed|                            |2011-11-02
          Component|libstdc++                   |c++
                 CC|                            |jason at gcc dot gnu.org
     Ever Confirmed|0                           |1
            Summary|complex<T> ctor drops sign  |[C++0x][constexpr]
                   |of zero (sometimes)         |complex<T> ctor drops sign
                   |                            |of zero (sometimes)
      Known to fail|                            |4.6.2

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-11-02 09:36:44 UTC ---
Confirmed.  Looks like a frontend issue (probably related to constexpr?).
In .initial we have

{
  struct mock_complex z1 = {._M_real=-0.0, ._M_imag=1.0e+0};
  struct complex z2 = {._M_value=__complex__ (0.0, 1.0e+0)};

  <<cleanup_point   struct mock_complex z1 = {._M_real=-0.0,
._M_imag=1.0e+0};>>;

thus z2 is already initialized from a bogus value.  Without -std=c++0x we have

  struct complex z2;
  <<cleanup_point <<< Unknown tree: expr_stmt
  std::complex<double>::complex (&z2, -0.0, 1.0e+0) >>>>>;

which is correct.