[Bug c++/25355] New: reinterpret_cast<> yields different (and incorrect) results when using -O2

["jason dot elbaum at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

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