When is the vtable used?

Question

Is the vtable only used for virtual function lookups, or does it get used for normal member function lookups as well?

Answer 1

Technically, this is an implementation detail. The C++ standard says nothing about vtables or vptrs.

But typically, a compiler will only choose to use the vtable/vptr mechanism when a member function is being called in a polymorphic sense (i.e. via a pointer/referene to base class). If it knows at compile-time what to do, then there's no need for the indirection.

Answer 2

Only for virtual function lookups. A non-virtual member function doesn't require much special -- it's just a normal function that receives this as a hidden parameter.