New LRUCache causing core dump

>> Clearly, we cannot release with a broke PointerFinder.  So, what's the
>> best fix folks?  My first reaction is a guard in Array>>#isLiteral?
>>
>>      isLiteral
>>           ^ self class == Array and: [ (self includes: self) not and:
>> [ self allSatisfy: [ : each | each isLiteral ] ] ]
>
> And, actually, the above doesn't work because LRUCache has the
> original Array two levels below...
>

> Hi Levente, the new structure of LRUCache seems to expose a problem
> with chasing pointers.  When I try to chase pointers to any object,
> one of the LRUCache's
>
> I'm still digging to try and see whether its a bug with chasing
> pointers or just a stack-depth limitation.  What I see so far is that
> PointerFinder wants to ask whether the 'head' var of the new LRUCache
> #isLiteral.  That is what leads to the VM crash.
>
>    (LRUCache allInstances anyOne instVarNamed: 'head') isLiteral
>
> I noticed the 'head' var is initialized as a two-element Array, with
> each element being the array itself.  So trying to ask an Array
> #isLiteral won't work in that case, e.g.,
>
>     |a| a:=Array new: 1.
>     a at: 1 put: a.
>     a isLiteral
>
> causes the same issue.
>
> Clearly, we cannot release with a broke PointerFinder.  So, what's the
> best fix folks?  My first reaction is a guard in Array>>#isLiteral?

> On Sun, 2 Feb 2014, Chris Muller wrote:
>
> >Hi Levente, the new structure of LRUCache seems to expose a problem
> >with chasing pointers.  When I try to chase pointers to any object,
> >one of the LRUCache's
> >
> >I'm still digging to try and see whether its a bug with chasing
> >pointers or just a stack-depth limitation.  What I see so far is that
> >PointerFinder wants to ask whether the 'head' var of the new LRUCache
> >#isLiteral.  That is what leads to the VM crash.
> >
> >   (LRUCache allInstances anyOne instVarNamed: 'head') isLiteral
> >
> >I noticed the 'head' var is initialized as a two-element Array, with
> >each element being the array itself.  So trying to ask an Array
> >#isLiteral won't work in that case, e.g.,
> >
> >    |a| a:=Array new: 1.
> >    a at: 1 put: a.
> >    a isLiteral
> >
> >causes the same issue.
> >
> >Clearly, we cannot release with a broke PointerFinder.  So, what's the
> >best fix folks?  My first reaction is a guard in Array>>#isLiteral?
>
> So the cause of the problem is PointerFinder >> #follow:from:. I see two
> problems there:
> 1. it sends #isLiteral to improve performance, but it can't really save
> much
> 2. it rejects all objects having a weak class (via
> #shouldFollowOutboundPointers), but those objects can have instance
> variables (e.g. WeakFinalizerItem), which are strong references.
>
> See Tools-ul.518 in the Inbox with my proposed fix.
>
>
> Levente
>
> P.S.: There was a comment in the earliest version in my image:
>
> "Remove this after switching to new CompiledMethod format --bf 2/12/2006"
>
> It's not clear what _this_ means, but your latest version (cmm 5/26/2013)
> lacks the comment, but no logic was removed.