Re: [Help-smalltalk] ObjectSpaces

[Paolo Bonzini]

On 10/20/2010 11:47 PM, Gwenaël Casaccio wrote:
> Hi,
>
> I would like to present a simple concept "ObjectSpaces":
> grouping all objects inside  an objectspace, each time
> that we send a message to another OS each of the
> OSes will intercept the message.

This will need to go for performance reasons.  However, maybe it's 
enough to have some _primitives_ redirected to the father ObjectSpace 
when the child ObjectSpace causes them.

Also, an ObjectSpace should be able to create another OS from scratch 
(you have an image loader written in Smalltalk, right?) rather than only 
as a clone of itself.  This is important for sandboxing, and allows the 
child OS to have no references to objects in the parent (while the 
parent can have arbitrary access).

On the other hand, it adds complexity for the VM because the classes 
will have a different OOP for each ObjectSpace (and symbols too, but 
maybe those could be shared if we decide that it's impossible to change 
an object from read-only to read-write).  Context switches don't have to 
be extremely fast, however.

Alternatively, or in addition to this, ObjectSpaces could send events 
between themselves.  This allows to implement an actor model.

> I guess we could use them as kind
> of transactional worlds (i.e. Worlds: Controlling the Scope of Side Effects
> http://lambda-the-ultimate.org/node/3040).

Yes, that makes for very easy atomic loading.

> I've made several implementation of the OSes  the most advanced
> had multiple object tables

Multiple object tables are the way to go.

Paolo