[Vm-dev] Problem with Proxies, objects and MethoDict

[Mariano Martinez Peck]

On Wed, Sep 29, 2010 at 2:25 PM, Mariano Martinez Peck <
marianopeck at gmail.com> wrote:

>
> Anyway, I tried it with
>>
>> | o p |
>> o := MyClass new.
>>
>> o foo: 123.
>> p := ClassProxy new.
>> p become: MyClass.
>> MyClass flushCache.
>> ClassProxy flushCache.
>> o == nil.
>> Transcript show: o class name; cr.
>> o foo.
>>
>> but same results.
>>
>> Now, something interesting is that "Transcript show: o class name; cr."
>> prints "MyClass". Is this correct?
>>
>>
> Grrrrr no, sorry, that's not true...can you believe there was a "
> Transcript cr; show: self name. "  in the fileout code ? heheheh
>
> Now I changed the proxy to extends Class (to see if it works) and at least
> it doesn't crash.
>
> "Transcript show: o class name; cr. " prints "a subclass of Object"  and
> after the evaluation of the code, I get the error:
>
> MessageNotUnderstood: a subclass of Object>>foo
>
> mmmmm
>
> I will continue investigating....
>


Something interesting is that after evaluating that code, and recieving the
error, MyClass which was:

Object subclass: #MyClass
    instanceVariableNames: 'foo'
    classVariableNames: ''
    poolDictionaries: ''
    category: 'Proxies'

now it is:

Object subclass: 'a subclass of Object'
    instanceVariableNames: ''
    classVariableNames: ''
    poolDictionaries: ''
    category: 'nil'


weird....

thanks!

mariano


>
>>
>>
>>> 2. you became from a class with N inst vars to one with N+M inst vars and
>>> the methods of the new class accessed inst vars > N which are off the end of
>>> your instance, causing the VM to read invalid oops and boom.
>>>
>>>
>> My case is even more complicated. I want to become from a CLASS to an
>> INSTANCE. I mean, I want to become the class MyClass with AN INSTANCE of
>> PROXY CLASS. Then the proxy class uses te DNU to bring the other back.
>>
>> Now I was thinking that maybe the proxy class should not extend from
>> ProtoObject but from Behavior or similar?  But I want smaller objects...I
>> don't want to spend instances in "uperclass methodDict format'"  since the
>> only thing I have to do is with DNU bring back other object.
>>
>> Finally, I have a question. I tried to look at the #become but I didn't
>> get it... When I do a become from a class to an object for example, if there
>> were (normal) pointers (slots in other objects) to that class, then they are
>> updated and point to the other object. However, what happens with the
>> instances of that class?  is the class pointer in their object header
>> consider like a normal pointer? are those piointers updated also by the
>> #become?    Maybe they are not and this is why  "Transcript show: o class
>> name; cr."   prints "MyClass"   ?
>>
>> Sorry for the newbie question...I am learning all this...
>>
>> Cheers
>>
>> Mariano
>>
>>
>>
>>> So a) always flush the method lookup cache and b) /never/ cause the VM to
>>> read past an object by changing the class underneath an object such that the
>>> class accesses more inst vars than the instance has.
>>>
>>>
>>>> how can I solve it ?
>>>>
>>>> Thanks in advance
>>>>
>>>> Mariano
>>>>
>>>>
>>>
>>>
>>
>
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