The problem with that (in C++) would be that A a; A* p = new A; assert(sizeof(*p) == sizeof(a)); This wouldn't be true and cause all sorts of trouble (a

The problem with that (in C++) would be that A a; A* p = new A; assert(sizeof(*p) == sizeof(a)); This wouldn't be true and cause all sorts of trouble (arrays, etc.) if a had no pointer to a vtable, but *p did. Moreover, you can take the address of a stack/member object, so how would you distinguish the two types? You'd literally need to modify the type system, and that would cause trouble with templates, etc.