Re: [Squeak-VMdev] Versiojn 4 changes

[Andreas R. <and...@gm...>]

Tim,

> I've this sort of thing several times before and so far as I can recall
> there are two basic approaches
>
> 1) Create a format of object that allows a memory pointer to some other
> place. I'd really hate to see this more complicated than allowing
> just not-oops in an object; mixing real oops and external pointers....
> euch. Primitives encapsulate access easily enough. Needs gc support to
> free external blocks when object dies. Ugly with a scavenger IIRC.

Yup. Wouldn't want to go that way. Much too complex for what I really need.

> 2) Allow object allocation outside ObjectSpace. Did this for Interval
> and I think Ian might be using the rump-version of this that I used to
> have for the RISC OS DisplayScreen. Main problem is with OSs- it's a
> pain to not have a uniform allocation direction. My memory is that Mac
> and RISC OS would allocate new outside-objects above ObjectSpace and
> Windows would do it below. Since one of the things you need to do is
> have a quick way to handle the young/old object decision, Windows was a
> bugger - no simply saying addr>youngStart => young object.

Doesn't matter for bits - the above is the precise reason for the
restriction towards bit objects.

> With either approach you have the obvious issue of sandbarring. This
> might not be considered a problem for big desktop machine with virtual
> memory but it could be a major pain for PDAs and embedded systems.
> Let's make sure we don't block anyone out.

Sorry, didn't get this - what do you mean with "sandbarring"?

Cheers,
  - Andreas