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 eas

Answer 1

As several other answers have mentioned, the return type of the function doesn't participate in the function signature, so both declarations are equivalent as far as making the assignment operator unusable by clients of the class.

Personally I prefer the idiom of having a class privately inherit from an empty non-copyable base class (like boost::noncopyable, but I have my own so I can use it in projects that don't have boost available). The empty base class optimization takes care of making sure there's zero overhead, and it's simple, readable, and doesn't rely on the dreaded preprocessor macro functionality.

It also has the advantage that copy and assignment can't even be used within class implementation code - it'll fail at compile time while these macros will fail at link time (likely with a less informative error message).