[Bug optimization/12484] New: virtual function yields bogus value when returning float constant (-O3 -fPIC)

[jonathan at cdnorthamerica dot com]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12484

           Summary: virtual function yields bogus value when returning float
                    constant (-O3 -fPIC)
           Product: gcc
           Version: 3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jonathan at cdnorthamerica dot com
                CC: gcc-bugs at gcc dot gnu dot org

here's the code to reproduce the error...

//----
#include <iostream>

class Foo
{
public:
  Foo() : _value(1) {}
  virtual ~Foo() {}

  virtual float getValue() const { return float(1); }
  virtual float getMemberValue() const { return _value; }

private:
  float const _value;
};


void
useFoo(Foo const &f)
{

  std::cout << std::endl
	    << "Foo const &f; " 
	    << std::endl;

  std::cout << " f.getValue() = " 
	    << f.getValue()
	    << std::endl;

  std::cout << " f.getMemberValue() = " 
	    << f.getMemberValue()
	    << std::endl;
}



int
main()
{
  Foo foo;

  std::cout << std::endl
	    << "Foo foo; " 
	    << std::endl;

  std::cout << " foo.getValue() = " 
	    << foo.getValue()
	    << std::endl;

  std::cout << " foo.getMemberValue() = " 
	    << foo.getMemberValue()
	    << std::endl;

  useFoo(foo);

}
//---

note:

1) problem occurs with -O3 and -fPI; dropping to -O2 and/or omitting -fPIC
eliminates problem

2) bogus results occur only when returning constant (e.g. return float(1); );
returning member data is o.k. (e.g. return _value)

3) bogus results occur only when given const reference to object having virtual
member; seems to work o.k. given the object itself

4) g++ 3.3.1 gives same behavior