Re: Simultaneous destructors

> I can offer a hand-wavy argument about why I think that state divergence
> makes protocols harder to reason about.
>
> is a protocol that allows state to permanently diverge.  When reasoning
> about this protocol, I need to keep the "branch" of the divergence in
> mind, and consider two paths (states synced, states not).  Now, I could
> take this same pattern, recursively graft it into S1 and S2, and now I
> have two more branch points.  So there are 6 stable states in the
> protocol, and my C++ code has to keep track of two levels of possibly
> different paths taken through parent/child.  Then recursively graft ...

Perhaps we could set a limit on how many such divergences a protocol
is allowed
to have.  We certainly don't need to support the sort of example
you're giving.

> It seems desirable to me that we do not require acknowledging every message:
> when the channel has data available, it sends that data along and doesn't
> cache it.

I agree with bsmedberg here.  But I can start by seeing how much of a
pain it is
to cache data if we can't modify IPDL (or do it in time: it hopefully
won't be
long).

> I understood |discard| to be a mechanism that allows you to tell the compiler
> exactly what you wrote above, that a message is no longer needed.

Your proposal for |discard| sounds fine.

Jason