> So, it is as always a balance between function and performance. Is
> enforcable
> runtime privacy worth a couple of cycles added to a two or three hundred
> cycle send routine? What do people think?
> 
As a separate VM, yes.  I don't think this needs to be enforced at runtime
in the standard VM; it uses extra cycles.  But I'd like to see Squeak
capable of building a separate VM out of the same, or similar, code in
Interpreter and ObjectMemory that *is* capable of this checking.  My guess
is that the personal-use Squeakers would use the faster VM, and that awkward
buggers like me who need multi-user security would use the slower one.  In
my case, *much* slower, as there are access-control lists on all object
accesses as well [plus an optimisation for the common case].

Tim, I hadn't realised you'd cleaned up the headers so much; I'll download
one of your VMs and images forthwith and restart my half-built
implementation of this.  Having even one spare bit in the CompiledMethod
header will be just *so* handy...

		- Peter