[Vm-dev] Finding pointers via heap walking and contexts

[Igor Stasenko]

ahh.. idioto, of course it can't find:

because i rejecting it:

(pointers reject: [ :ptr |
        (ptr isContext and: [ ptr callChainAnySatisfy: [ :ctx | ctx ==
bottomContext ] ]) or: [ (exceptions identityIncludes: ptr) or:
[ptr==exceptions] ]]) asArray

while i wanted to reject all contexts is on top of bottomContext or the
bottomContext itself,
but not below it,
but this condition actually means: 'reject any context if it on same stack
as bottomContext'

:)




On 29 August 2013 19:40, Igor Stasenko <siguctua at gmail.com> wrote:

>
>
>
> On 29 August 2013 18:34, Eliot Miranda <eliot.miranda at gmail.com> wrote:
>
>>
>>
>>
>>
>> On Thu, Aug 29, 2013 at 8:54 AM, Igor Stasenko <siguctua at gmail.com>wrote:
>>
>>>
>>> Hello,
>>>
>>> i tried to implement a simple algorithm to find nearest common roots for
>>> some object(s)..
>>> see the attached code.
>>>
>>> The problem i discovered that the last assertion of my test fails:
>>> =====
>>> testArrayShouldBeRootOfItsElements
>>>
>>>     | obj1 obj2 array arrayToTest roots |
>>>
>>>     obj1 := 'ObjectA' copy.
>>>     obj2 := 'ObjectB' copy.
>>>
>>>     array := {  obj1. obj2 }.
>>>     arrayToTest := { obj1. obj2 }.
>>>
>>>     roots := CommonRootsFinder new findCommonRootsOf:  arrayToTest.
>>>
>>>     self assert: (roots identityIncludes: array).
>>>     self assert: (roots identityIncludes: arrayToTest) not.
>>>     self assert: (roots identityIncludes: thisContext).  "- sometimes
>>> works , sometimes not "
>>> ========
>>>
>>> but, when i restart the method in debugger and step down through it,
>>> assertion DOES NOT fails.
>>> This means that memory scan does not reveals this context as it should
>>> be.
>>>
>>> (maybe because it stops at the object which located before location of
>>> thisContext)?
>>>
>>
>> That would make sense.  For debugging, why don't you record the objects
>> visited in an OrderedCollection, and then you can look at what order the
>> pointer finder found them.
>>
>>
>
> well, if you look at algorithm:
>
>     pointers := IdentitySet new.
>     object := self someObject.
>     [ object == pointers ] whileFalse: [
>         1 to: objects size do: [ :i | ((object pointsTo: (objects at: i))
> and: [ (object pointsOnlyWeaklyTo: (objects at: i)) not]) ifTrue: [
> pointers add: object ]  ].
>         object := object nextObject ].
>
> since the 'pointers' is the last object created on heap, and the subject
> context
> must exist before entering this method, it should eventually find it..
> but as it appears it doesn't..
>
> what i thinking, that maybe i should change the stop condition to
> [ object == 0 ]
> (which primitive returns when there is no more object on heap),
> like that i can be sure that i will visit every heap-allocated object..
> But that is tricky because then loop may never stop if there is new
> object(s) created (like in #add: ) in loop body..   :(
>
>
>
>
>>> any suggestions/comments/ideas , how to make sure that assert will never
>>> fail?
>>>
>>
>> Doesn't that depend on how you've implemented CommonRootsFinder?
>>
>>
>>> --
>>> Best regards,
>>> Igor Stasenko.
>>>
>>>
>>
>>
>> --
>> best,
>> Eliot
>>
>>
>
>
> --
> Best regards,
> Igor Stasenko.
>



-- 
Best regards,
Igor Stasenko.
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