On Wed, Nov 20, 2013 at 6:53 AM, Riccardo Manfrin <riccardomanfrin@xxxxxxxxx> wrote: > > suppose I have three classes Foo, Bar, Zoo. > > Foo inherits from Bar, > Bar inherits from Zoo. > > Bar and Zoo are abstract classes (as defined here : > http://en.wikibooks.org/wiki/C%2B%2B_Programming/Classes/Abstract_Classes) > > The size of Foo shall account for the two pointers to Bar an Zoo vtables. For this kind of discussion it helps to show actual code. If I understand your description correctly, then your statement about the size of Foo is incorrect. #include <iostream> class Zoo { virtual void zoo() = 0; }; class Bar : public Zoo { virtual void bar() = 0; }; class Foo : public Bar { void* v; }; int main() { std::cout << sizeof(Foo) << std::endl; } On my x86_64 system this prints 16: 8 for the single vtable pointer, 8 for the void* field. In other words, although Foo inherits from two classes as you suggest, there is still only one vtable pointer. Ian
