Function Pointers in C++

Just discovered some interesting facts about function pointers in C++. Here I am giving a short summary.

Different compilers may treat function pointer operations in different ways. For the output operation cout <<, MSVC10 can print the actual address for general function pointers, but g++ will print a bool value 1. However, if casted to void * type, both MSVC and g++ can display the actual address.

For class member functions, MSVC works the same way as g++, and both would output a bool value without casting. One more point is that C++ standard does not allow class member pointers be casted to void * type. Therefore, we have no way to get the real address unless we use the printf function.

Here are a sample program and its outputs by MSVC and g++.

Output by MSVC:

Output by g++:

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Some more thinking about this 2 days after the original posting. I just found another special case in which both MSVC and g++ work exactly the same way for function pointers. Also, this may explain why g++ prefers to output a bool value for general function pointers in the statement cout << fp.

The special case is related to stream manipulator! Actually, stream manipulators are function pointers with the prototype ostream & manipulator( ostream & ). Seems that C++ library has already overloaded the case cout.operator<<( ostream & func(ostream &) ) and it will actually execute func( ostream & ) and returns ostream &. For all other function names or function pointers, it will return a bool value.