Ambiguous conversion with gcc 3.3/3.4

[Olivier FOURDAN <olivier.fourdan@xxxxxxxxxxxxxx>]

Hi all,

We have the following error occuring with both gcc 3.3 and 3.4 while the 
exact same code compiled w/out any warning with gcc 2.95. I understand 
that gcc 3.4 is *"much* closer to full conformance to the ISO/ANSI C++ 
standard", but I'm not sure I fully get the point of the error, and how 
to get rid of the ambiguity (in a simple manner ;) ).

./testgcc.cc: In member function `void Y::f()':
./testgcc.cc:65: error: ISO C++ says that these are ambiguous, even 
though the worst conversion for the first is better than the worst 
conversion for the second:
./testgcc.cc:40: note: candidate 1: bool operator==(const T*, const 
_NULL_PTPL_RUNTIME_&) [with T = Y]
./testgcc.cc:65: note: candidate 2: operator==(Y*, Y*) <built-in>

Thanks in advance for your help,

Cheers,
Olivier.

The sample "testgcc.cc" code follows:

//----8<--------8<--------8<---- CUT HERE ----8<--------8<--------8<----//
class _NULL_PTPL_RUNTIME_
{
public :
   template<typename T> operator T*() const  ;
   template<typename T> bool operator ==(const  T *right) const ;
   template<typename T> bool operator !=(const  T *right) const ;
  
   _NULL_PTPL_RUNTIME_() {};
   ~_NULL_PTPL_RUNTIME_() ;
  
static const _NULL_PTPL_RUNTIME_ _null_ ;
  
private :
   void operator &() const  ;
   _NULL_PTPL_RUNTIME_(_NULL_PTPL_RUNTIME_ &copyOf) ;
} ;

template<typename T>
_NULL_PTPL_RUNTIME_::operator T*() const
{
   return (0);
} ;

template<typename T> bool 
_NULL_PTPL_RUNTIME_::operator ==(const  T *right) const 
{
   return (right==(T*)0);
} ;

template<typename T> bool 
_NULL_PTPL_RUNTIME_::operator !=(const  T *right) const 
{
   return (right!=(T*)0);
} ;

#undef NULL
#define NULL _NULL_PTPL_RUNTIME_::_null_

template<typename T> bool operator ==(const T *left ,const  
_NULL_PTPL_RUNTIME_ &right) 
{
   return (right.operator ==(left));
};

template<typename T> bool operator !=(const T *left ,const  
_NULL_PTPL_RUNTIME_ &right) 
{
   return (right.operator !=(left));
};   


class X
{
   public:X() ;
};

class Y:X
{
   public:Y();
   void f();
} ;

void
Y::f()
{
   Y *y = NULL;
   if (y == NULL)
   {
       /* void for now */
   }
} ;