From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-368552-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 8315 invoked by alias); 23 Sep 2011 23:50:11 -0000
Received: (qmail 8307 invoked by uid 22791); 23 Sep 2011 23:50:10 -0000
X-SWARE-Spam-Status: No, hits=-2.9 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; Fri, 23 Sep 2011 23:49:56 +0000
From: "giecrilj at stegny dot 2a.pl" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/50501] New: Insertion of complex into a stream may fail without invalidating the stream
Date: Sat, 24 Sep 2011 00:35:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: libstdc++
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: giecrilj at stegny dot 2a.pl
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-50501-4@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: 2011-09/txt/msg01729.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50501

             Bug #: 50501
           Summary: Insertion of complex into a stream may fail without
                    invalidating the stream
    Classification: Unclassified
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: giecrilj@stegny.2a.pl
              Host: x86_64-suse-linux
            Target: x86_64-suse-linux
             Build: x86_64-suse-linux


I can see the following implementation in <complex>:

///  Insertion operator for complex values.
  template<typename _Tp, typename _CharT, class _Traits>
    basic_ostream<_CharT, _Traits>&
    operator<<(basic_ostream<_CharT, _Traits>& __os, const complex<_Tp>& __x)
    {
      basic_ostringstream<_CharT, _Traits> __s;
      __s.flags(__os.flags());
      __s.imbue(__os.getloc());
      __s.precision(__os.precision());
      __s << '(' << __x.real() << ',' << __x.imag() << ')'; // This can fail!
      return __os << __s.str(); // And then this may be empty!
    }

This implementation may cause the following test case to fail:

#include <cstdlib>
#include <cassert>
#include <iostream>
#include <complex>

int main () { float const a_f ((01));
    ::std:: complex < float > a_c ((a_f)); std:: stringstream a_s; 
    assert 
(!(a_s << a_c) || ((a_c = float ()) == float () && a_s >> a_c && a_c == a_f));
    return +EXIT_SUCCESS; }

I cannot reproduce the failure because I do not know how to inject a memory
allocation failure.  However, I imagine it is possible.

I suggest that the implementation be modified:

///  Insertion operator for complex values.
  template<typename _Tp, typename _CharT, class _Traits>
    basic_ostream<_CharT, _Traits>&
    operator<<(basic_ostream<_CharT, _Traits>& __os, const complex<_Tp>& __x)
    {
      basic_ostringstream<_CharT, _Traits> __s;
      __s.flags(__os.flags());
      __s.imbue(__os.getloc());
      __s.precision(__os.precision());
      __s << '(' << __x.real() << ',' << __x.imag() << ')';
      __os. setstate(__s.rdstate()) ;
      return __os << __s.str();
    }

Thank you for your consideration.