Re: refcount checking in add_interface

[Maciej Stachowiak <mjs eazel com>]

Nat Friedman <nat@helixcode.com> writes:

> Please add this check back.
> 
> Or, if you want to go a step further, you can enforce the actual
> invariant which matters; that is, after someone QI's for an interface,
> we must always give the same answer in the future.  The invariant is:
> 
>     If QI (component, "interface") returns a valid interface, it must
>     always return a valid interface.  If QI (component, "interface")
>     returns NIL, it must always return NIL.

The only way this invariant differs from "you may not add or remove an
interface after exposing an object" is that it allows the component to
add or remove an interface that has not been QI'd for yet. Is that a
useful difference? I can't imagine why an object would want to do this
rather than assembling all its interfaces ahead of time.

What I'd like to do is give the aggregate object some specific bit
indicating whether any of its interfaces have been exposed through
CORBA, although I am not sure what a correct way to detect this is
(it's possible and perhaps even likely you'll get at least one
interface without ever doing a QI for it). If either of the objects
you are trying to merge, the operation will just fail.
 
 - Maciej