class Obj {...};

class MyFoo : public Foo, virtual public Obj {...};
class MyBar : public Bar, virtual public Obj {...};

class MyBaz : public Baz, virtual public Obj {...};


##</code><code>##

void *ptr = (void*) static_cast<Obj*>(foo);

##</code><code>##

Foo* foo = dynamic_cast<MyFoo*>((Obj*) ptr);