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

[Mariano Martinez Peck]

On Tue, Sep 28, 2010 at 11:12 PM, Igor Stasenko <siguctua at gmail.com> wrote:

>
> Here it is.
> Just be aware, that its not intercepting all messages.
> Some messages like #== or #class is early bound by compiler/VM,
> so even if you redefine them, their behavior won't be changed.
>
>
Thanks Igor. I am trying to understand your code.
Now...how I should use MessageCatchingProxy ?

how can I adapt this code to use your proxy?

| o p |
o := MyClass new.
o foo: 123.
p := ClassProxy3 new.
p become: MyClass.
MyClass flushCache.
ClassProxy3 flushCache.
o == nil.
Transcript show: o class name; cr.
o foo.


thanks a lot

mariano



> (I forgot where to get the list of these exceptional selectors).
> Smalltalk specialSelectors seems like not the same thing.
>





>
>
> On 28 September 2010 23:48, Bert Freudenberg <bert at freudenbergs.de> wrote:
> >
> >
> > On 28.09.2010, at 22:29, Mariano Martinez Peck wrote:
> >
> > Hi folks. I am trying to do something and I found a VM crash. Suppose I
> want to swap out a class, do a become with a proxy (that with the DNU will
> load the class back). In addition, I have instances of the swapped class.
> >
> > Example of code (will crash in the last line):
> >
> > o := MyObject new.
> > o foo: 123.
> > p := ClassProxy new.
> > p become: MyObject.
> > o == nil.
> > o foo.
> >
> >
> > My Object just extends Object, has an instVar 'foo',  and implements the
> accessors.
> >
> > ClassProxy implements:
> >
> > become: aClass
> >     className := aClass name.
> >     aClass fileOut.
> >     super become: aClass
> >
> > and
> >
> > doesNotUnderstand: aMessage
> >     | reloadedClass |
> >     (FileStream fileNamed: className, '.st') fileIn.
> >     reloadedClass := Smalltalk at: className.
> >     self becomeForward: reloadedClass.
> >     ^aMessage sendTo: reloadedClass
> >
> >
> > So....does someone know why the crash?
> >
> > Looks like o's class pointer does not point to a class after the become.
> When the VM tries to lookup #foo in o's class it crashes.
> >
> > how can I solve it ?
> >
> > I'd say you cannot get rid of a class if there are still instances of it.
> You can stub out the class however. If the method dict is nil, the VM will
> send cannotInterpret: if you send a message to an instance. You should be
> able to use that instead of #doesNotUnderstand:.
> > - Bert -
> >
> >
> >
>
>
>
> --
> Best regards,
> Igor Stasenko AKA sig.
>
>
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