Emptyness vs. virtualness

[Jason Merrill]

>>>>> "Mark" == Mark Mitchell <mark at codesourcery.com> writes:

>   struct A {};

>   struct B : public A {
>     virtual void f () {}
>   };

>   struct C : public virtual B {};

>   struct A2 : public A {};

>   struct D : public C, public A2 {
>   };

> Clearly C goes at offset 0.  Now, can A2 go at offset 0?

> We have a disagreement between two of our implementations; I'm trying
> to figure out if we actually decided this before or not.  Does anyone
> recall any traffic about this?

I don't.  My inclination would be to say that A2 cannot be at offset 0;
otherwise we would have to add a new B subobject for D.

Jason