vtables.cpp

#include <stdio.h>

extern "C" {
  void printi(int i) {
    printf("%d\n", i);
  }

  typedef void (*A_p)(struct A*);
  struct A {
    static void _new(struct A* self) {
      static char* vtable[] = {
        (char*)A::_p,
      };
      self->p=(A_p*)&vtable[0];
    }
    A_p* p;
    static void _p(struct A* self) {
      printi(1);
    };
  };

  typedef void (*B_p)(struct B*);
  struct B {
    static void _new(struct B* self) {
      static char* vtable[] = {
        (char*)B::_p2,
      };
    	self->p2=(B_p*)&vtable[0];
    }
    B_p* p2;
    static void _p2(struct B* self) {
      printi(2);
    }
  };


  struct C {
  	struct A a;
  	struct B b;
    static void _p2(struct B* self) {
      printi(33);
    }

    static void _new(struct C* self) {
      static char* vtable[] = {
        (char*)A::_p,
        (char*)_p2,
      };
      A::_new(&self->a);
      B::_new(&self->b);
      self->a.p = (A_p*)&vtable[0];
      self->b.p2 = (B_p*)&vtable[1];
    }

  };

  int main() {
    struct C c;
    C::_new(&c);
    (*c.a.p)(&c.a);
    (*c.b.p2)(&c.b);
    return 0;
  }
}