FAQ 17.06 Can a derived class pointer be converted into a pointer to its public base class?

Such conversions are possible and don't even require a pointer cast.

A publicly derived class is a kind-of its base class. By implication, the upward conversion is perfectly safe, and is quite common. For example, a pointer to a Car is in fact already pointing at a Vehicle, since a Car is a kind-of a Vehicle.

 class Vehicle { }; class Car : public Vehicle { }; void f(Vehicle* v) throw(); void g(Car* c) throw() {   f(c);  //Perfectly safe; no cast needed }