FAQ 38.03 What is one of the most common errors when using pointers to member functions?

Trying to pass the address of a nonstatic member function into a function that is expecting a pointer to function, and sometimes the inverse of this scenario.

Nonstatic member functions have an implicit parameter that points to the object the pointer called this inside the member function. Nonstatic member functions can be thought of as having a different calling convention from that of normal C functions, so the types of their pointers are different and incompatible pointer to nonstatic member function versus pointer to function.

C++ introduces a new type of pointer, called a pointer to nonstatic member, which can be invoked only by providing an object. Do not attempt to cast a pointer that points to a nonstatic member function into a pointer to function or vice versa; the result is undefined and probably disastrous. For example, a pointer to nonstatic member function probably doesn't contain the machine address of the appropriate function. As noted in the last example, if a regular C function pointer is needed, use either a static member function or a nonmember function.