Virtual Calls: Make the ABI match the implementations

[Jason Merrill]

>>>>> Christophe de Dinechin <ddd at cup.hp.com> writes:

 > The proposal is that thunks are implemented as weak symbols (as they are
 > generally today.) If an implementation decides to emit fall-through thunks,
 > then it emits these thunks along with the function, as strong symbols. In
 > that case, they will take precedence at link time.

Only if they are seen first.  Under the SVR4 ABI, a weak defn followed by a
strong defn produces a multiply-defined symbol error.

Many vendors break from this spec and allow the later strong defn to
override the earlier weak, but not all.  SCO, for instance, doesn't.

Perhaps the base ABI committee would consider changing this.

Jason