[Bug c++/24804] New: Produces wrong code

[abottema at mathworks dot com]

Compile the following program (minimized from a larger context) with
'g++ -O3 -fno-strict-aliasing foo.cpp' (on a Linux i386 32-bit machine
with gcc 3.4.4)

foo.cpp:
===================================================================
class DummyType
{
public:
    inline DummyType() { }
    inline ~DummyType() { }
};

class Foo
{
public:
    Foo() : X0(0), X4(0) { }

    int X0, X1, X2, X3, X4;
};

int main()
{
    {
        Foo f;
        DummyType();
    }

    Foo f2;
    while (1) {
        if (f2.X4 != 0) {
           f2.X4 = 0;
        } else {
           break;
        }
    }

  return 0;
}
=================================================================

It will hang if you execute it.

It does not hang if you do _one_ of the following things:

- Compile with -O1 (instead of -O3)
- Remove compiler flag -fno-strict-aliasing
- Replace all occurrences of 'f2.X4' with 'f2.X3'
- Remove the statement 'DummyType();'
- Remove the statement 'Foo f;'


-- 
           Summary: Produces wrong code
           Product: gcc
           Version: 3.4.4
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: abottema at mathworks dot com
 GCC build triplet: ix86-linux
  GCC host triplet: ix86-linux
GCC target triplet: ix86-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24804