[gclist] Regions and collection.

[Paul Haahr]

Charles Fiterman wrote
> Regions break type safety the same way free does. You can have a
> pointer to a freed object, wait for something you want to see the
> insides of to occupy that space and take over.

Just to be clear, Mads Tofte's region work is tied to the type system
and entirely type safe.  It has the drawback that objects whose lifetime
can't be determined statically end up living a very long time.  Think of
it as dynamic extent analysis on steroids.

I keep wondering if there's a way to usefully combine regions with
gargabe collection.  Last time I read the papers on region analysis,
they were mutually exclusive.

--p