[Vm-dev] Special objects array - sometimes everybody cannot be special

[Igor Stasenko]

I thought hard how to avoid using spl object in VM code to check
that an object, which contains a weak ref which just died,
needs a special handling (add it to list, which is in it's first ivar).

So, if there is such scheme, which i don't see, then we could avoid
adding a new special object to support new finalization scheme.

On 25 May 2010 08:19, Igor Stasenko <siguctua at gmail.com> wrote:
> On 25 May 2010 06:56, David T. Lewis <lewis at mail.msen.com> wrote:
>>
>> We have some contention for slots in the special objects array. The Alien
>> package lays claim to slots 50 - 54, and Igor's improved finalization
>> would like to use slot 50. The Alien claim predates the Finalizer claim
>> (albeit only through an *Extentions in Alien-VMMaker-Support), and there
>> may already be people running VMs that rely on these special object
>> assignments. On the other hand, finalization is part of the core system,
>> so it would have been nice to put ClassWeakFinalizer at slot 50, and the
>> optional Alien assignments at 51 - 55.
>>
>> Would anyone object to the following allocation of slots in the special
>> objects array? This would leave Alien mostly unaffected, but would require
>> Igor's finalization improvements to put WeakFinalizer at position 55 in
>> the special objects array, and it would require that the Alien override
>> be pulled into the VMMaker package such that all VMs would have the Alien
>> assignments in the special objects array (albeit unused in many cases).
>> And recreateSpecialObjectsArray would need updates to match of course.
>>
>>        SelectorAttemptToAssign := 50.
>>        "PrimErrTableIndex := 51. in Interpreter class>>initializePrimitiveErrorCodes"
>>        ClassAlien := 52.
>>        InvokeCallbackSelector := 53.
>>        ClassUnsafeAlien := 54.
>>        ClassWeakFinalizer := 55
>>
>> I seem to recall some discussion of a more flexible special objects
>> registry, although I can't find it right now. Pointers welcome.
>>
>
> Ouch.. David, it seems like i used the different version of
> #recreateSpecialObjectsArray
> than yours.
>
> The tail of spl objects in Alien-Core package, found at  SqS/Alien
> looks like following:
>
>        newArray at: 50 put: #run:with:in:.
>        newArray at: 51 put: nil.
>        newArray at: 52 put: nil.
>        newArray at: 53 put: (self at: #Alien ifAbsent: []).
>        newArray at: 54 put: #invokeCallback:stack:registers:jmpbuf:.
>        newArray at: 55 put: (self at: #UnsafeAlien ifAbsent: []).
>
> So, i thought its not a problem to reserve the 51 slot for weak
> finalization, because it unused anyways.
>
> Also, maybe we could fill an unused/obsolete slot instead of allocating new one?
>  There are some:
>
>        newArray at: 23 put: nil.
>        newArray at: 41 put: nil.
>
>> Dave
>>
>>
>
>
>
> --
> Best regards,
> Igor Stasenko AKA sig.
>



-- 
Best regards,
Igor Stasenko AKA sig.