[Vm-dev] [Pharo-project] Plan/discussion/communication around new object format

Igor Stasenko siguctua at gmail.com
Sat Jun 16 02:28:30 UTC 2012

On 16 June 2012 03:42, Levente Uzonyi <leves at elte.hu> wrote:
> On Thu, 14 Jun 2012, Igor Stasenko wrote:
>>> To be honest, I'm a little puzzled by the resistance to immutability.
>> and also, because i am strong proponent of reducing a number of
>> contracts between VM and language.
>> Things, like moving scheduling logic to image side, moving identity
>> hash logic to image side etc etc.
>> which makes VM less complex, by having less contracts.
>> This is a part of my holy crusade against complexity :)
> IIUC you want to push stuff from VM side to the image. And you want to add a
> properties slot for all objects in the new VM. Why don't you do that in the
> image? It's the same as adding an instance variable to Object/ProtoObject,
> isn't it? :)
In theory yes, but in practice, existing object format(s) do not allow
you to do that:
try adding instance variable to any variable class with bytes/words format.

So, one way or another you will need to change the object format to allow that.
And if VM would allow you to do things like you describing, then it
will be even better - no extra responsibility from VM, just add an
instance var.
But your smiley at the end means irony, like i proposing something
very silly, right?

So allow me also be ironic/moronic a bit..

Just take a look at nice and beautiful implementation of dependents
protocol of Object.
So, every Object in system can have additional property , named "dependents".
Sounds close to what i proposing.. But of course it would be silly to
implement it differently
comparing to current implementation. For sure, you should use huge,
weak identity dictionary,
where you store this property.

But lets move on to Morphs.. ahhh yeah.. morphs came to us from Self
where any object
could have as many properties as it wants. But since we cannot afford
that, what we do?
Yeah, we build a piles of mess, then call it MorphExtension and
everyone happy, and keep *rolling eyes* at silly idiots like me.

And the last thing.. you could ask: where is Compiled methods store
their properties, like pragmas etc?
I will answer: At very obvious and right place where you can find it,
it is just needs some elaboration:
- second to last literal in it's literals array, unless it is reserved
by method's selector,
then it is held by "AdditionalMethodState", very similar to what both Object and
MorphExtension doing.
Do doubt, if you do it any other way, you will be just an idiot!

And sure thing, all of these examples showing very beautiful and
elegant way how we should organize an object's data structure, when
you cannot predict in advance, how many properties it may need.

Best regards,
Igor Stasenko.

More information about the Vm-dev mailing list