c++ - Macros to disallow class copy and assignment. Google -vs- Qt

Question

To disallow copying or assigning a class it's common practice to make the copy constructor and assignment operator private. Both Google and Qt have macros to make this easy and visible. These macros are:

Google:

#define DISALLOW_COPY_AND_ASSIGN(TypeName) 
  TypeName(const TypeName&);   
  void operator=(const TypeName&) 

Qt:

#define Q_DISABLE_COPY(Class) 
  Class(const Class &);      
  Class &operator=(const Class &);

Questions: Why are the signatures of the two assignment operators different? It seems like the Qt version is correct. What is the practical difference between the two?

Answer 1

It doesn't matter. The return type is not part of a function's signature, as it does not participate in overload resolution. So when you attempt to perform an assignment, both declarations will match, regardless of whether you use the return type.

And since the entire point in these macros is that the functions will never get called, it doesn't matter that one returns void.