TITLE: Casting of member function pointers

PROBLEM: pete@borland.com (Pete Becker)

	Now watch what happens when the callback tries to call this function
with two pointers to ints instead of two pointers to doubles. As ever, using
a cast to throw away information can result in throwing away too much
information. Here's a better way:

	typedef int (CallBackBase::*COMethod)(int*,int*);
	template <class T> 
	Callback CreateCallback( T& t, int (T::*func)(int*,int*))
	{
	return Callback(&t,(COMethod)f);
	}

The template function guarantees that we don't get the parameter types wrong,
which makes the cast of the pointer-to-member-function into COMethod safe.


RESPONSE: jamshid@emx.cc.utexas.edu (Jamshid Afshar)

No, that is still not safe.  [deleted] this is still not safe because all
member function pointers are not guaranteed to have the same size or
representation.  For example, some compilers (like Borland C++ 3.1 :-) are
able to make the size of a member function pointer smaller if the class
does not contain any virtual functions or bases.