Does virtual inheritance and virtual function use the same vtable?

There is one little related question. But the topic is entirely different.

Now, one co开发者_如何学JAVAncept is about the function resolution and another is about class resolution ? I am wondering that how is it possible if they are using the same vtable (at least in gcc-4.5) ? Is this a compiler dependent terminology ?

I know that it might appear as basic silly question, but I had never thought of it.

A good reference for this sort of thing is the Itanium ABI - see eg http://mentorembedded.github.com/cxx-abi/abi.html#vtable. Despite the name it's a widely used ABI for C++ and it describes a good, working implementation (although obviously other implementations are possible).

You can solve both problems (virtual function calls and virtual inheritance) if you know the dynamic type of an object given just a pointer to it. Every (polymorphic) object in C++ has precisely one dynamic type, which is determined at the moment when it's constructed. E.g. when you write new Foo, that object has the dynamic type Foo even if you store just a void*.

A vtable is a mechanism to store information about the dynamic type of an object in such a way that it can be retrieved via a base pointer. You can store quite some things in a vtable: function pointers, cast offsets, std::type_info objects even.