Разве указатель не является просто адресом? Или я что-то упустил?

Я тестировал несколько типов указателей:

pointers to any variables is the same (8B on my platform) pointers to functions are the same size, as pointers to variables (8B again) pointers to functions with different parameters - still the same (8B)

НО указатели на функции-члены больше - 16B на моей платформе.

Три вещи:

Why are pointers to member functions bigger? What more information do they need? As far as I know, the standard says nothing about the size of a pointer, except that void* must be able to "contain" any pointer type. In other words, any pointer must be able to be casted to void*, right? If so, then why sizeof( void* ) is 8, while sizeof a pointer to member function is 16? Are there any other examples for pointers, that are with different size (I mean, for standard platforms, not some rare and special ones)?