- * sizeof(O) :: size of an object O
- * align(O) :: alignment of the object O
- * offset(C) :: offset of the component C within O
- * dsize(O) :: data size of the object O (without tail padding)
- * nvsize(O) :: the /non-virtual/ size of the object O (i.e.,
- without virtual bases)
- * nvalign(O) :: the non-virtual alignment of the object O
+ + Implement `indirect' slots and messages, which can be added (once a
+ class has declared support) /without/ breaking the class's ABI.
+ Indirect messages can be added to an indirect `vtmsgs' structure via
+ a pointer in the main vtable. Indirect slots must be added to a
+ region of the `ilayout' located via an offset stored in the vtable.