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* [Bug c++/25355]  New: reinterpret_cast<> yields different (and incorrect) results when using -O2
@ 2005-12-11 17:54 jason dot elbaum at gmail dot com
  2005-12-11 17:58 ` [Bug c++/25355] " pinskia at gcc dot gnu dot org
  0 siblings, 1 reply; 2+ messages in thread
From: jason dot elbaum at gmail dot com @ 2005-12-11 17:54 UTC (permalink / raw)
  To: gcc-bugs

The test case:

#include <iostream>

using namespace std;

int main()
{
    unsigned int test = 1067320345;

    cout << reinterpret_cast<float &>(test) << endl;

    cout << "reinterpret_cast<float &>(test): " <<
      reinterpret_cast<float &>(test) << endl;
}


When compiled using -g or -O1, the correct output is produced:

1.2345
reinterpret_cast<float &>(test): 1.2345


When compiled using -O2, the first reinterpret_cast<> produces incorrect
results. The actual value produced depends on the OS:

-NaN
reinterpret_cast<float &>(test): 1.2345


I tested this on Solaris 8 and on Linux Redhat WS3, with identical results. My
conclusion is that we're looking at an optimizer bug.


-- 
           Summary: reinterpret_cast<> yields different (and incorrect)
                    results when using -O2
           Product: gcc
           Version: 4.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jason dot elbaum at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25355


^ permalink raw reply	[flat|nested] 2+ messages in thread
* [Bug c++/25355] reinterpret_cast<> yields different (and incorrect) results when using -O2
  2005-12-11 17:54 [Bug c++/25355] New: reinterpret_cast<> yields different (and incorrect) results when using -O2 jason dot elbaum at gmail dot com
@ 2005-12-11 17:58 ` pinskia at gcc dot gnu dot org
  0 siblings, 0 replies; 2+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-12-11 17:58 UTC (permalink / raw)
  To: gcc-bugs



------- Comment #1 from pinskia at gcc dot gnu dot org  2005-12-11 17:58 -------
You are violating C/C++ aliasing rules.


*** This bug has been marked as a duplicate of 21920 ***


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25355


^ permalink raw reply	[flat|nested] 2+ messages in thread
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2005-12-11 17:54 [Bug c++/25355] New: reinterpret_cast<> yields different (and incorrect) results when using -O2 jason dot elbaum at gmail dot com
2005-12-11 17:58 ` [Bug c++/25355] " pinskia at gcc dot gnu dot org

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