C++ multiple inheritance and vtables

Question

So going back to basics, I\'m trying to wrap my head around vtables and whatnot. In the following example, if I were to, say, pass a B* to some function, how does t

Answer 1

With multiple inheritance, the object gets built in parts, each part corresponding to one of the base classes. This includes the vtable pointers. This is necessary because the code interacting with a pointer or reference won't know if it's working with the base class or the derived one, so they must be laid out identically.

One surprising result is that when you cast a pointer to one of the base classes, its address may change! The compiler generates some code behind the scenes to adjust the pointer to the proper piece of the object.

C obj;
A* ap = (A*)&obj;
B* bp = (B*)&obj;
bool same = ((void*)ap) == ((void*)bp);  // false!