Stephen,

> I'm creating a "forwarder" capability.  In Squeak, due to the direct
> mapped memory model, a become: operation, under certain circumstances
> (large image, object in old space) can take a very long time (a half
> second or more).  Therefore, for certain applications, using become is
> not appropriate.

I forgot to mention this in my last post: If #become: speed is all that's
bothering you, there might be a way around it without having to modify the
VM too deeply. It depends whether you know enough the object you're proxying
and whether you're willing to trade some space.

What you could do is to make the forwarder exactly the same size size as the
object you're proxying. If both objects are of the same size then you can
just copy all the state from one object to the other and vice versa. There
are a few tricky implications (such as when #becoming: a compact with a
non-compact class and fixing up the roots table afterwards) but it may be a
lot simpler than modifying the VM in such a deep way that you're
anticipating.

Unless, of course, you're just doing a bit of VM hacking for the fun of it
;-)

Cheers,
  - Andreas