Vtable index type

[Jason Merrill]

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

 > We should specify a type for vtable indices.  It seems to me that
 > `ptrdiff_t' is the obvious candidate.

 > This is important in that it limits the number of vtable entries we
 > can use.  (For example, g++ has historically used `short' for a vtable
 > index; that limited the size of vtables.)

Where does a vtable index appear in the ABI?

Jason