Vbase offsets

[Jim Dehnert]

> From: Mark Mitchell <mark at codesourcery.com>
> 
> OK.  But, given:
> 
>   struct S {
>     virtual void f();
>   };
>   struct T : virtual public S {};
>   struct U : public T {};
>   
> Are there two vbase offsets for `S' in the vtable for `U'?  Here `T'
> is the primary base for `U', so the vtable for `U' already has an `S'
> entry.  I assume we don't want to add an extra one.  Maybe that
> example would be helpful, too?  What if `T' is inherited virtually?
> Then, `T' is still the primary base of `U', so I don't think we need
> an extra offset here either?  If I'm right, that's probably worth
> mentioning too.  So, I think the rule is:
> 
>   If there is no primary base class, then there is a vbase offset for
>   every direct or indirect virtual base.  Otherwise, a vbase offset is
>   present in the derived class for every virtual base that does not
>   already have a vbase offset in the primary base class vtable.  In
>   either case, the vbase offsets are allocated in reverse inheritance
>   graph order.

No, we shouldn't replicate vcall or vbase offsets from primary bases.
I've updated it, though not with exactly your language, and added
your example.  Take a look.

Jim

-	    Jim Dehnert		dehnert at sgi.com
				(650)933-4272