On Mon, Feb 03, 2014 at 06:40:44PM +0100, Levente Uzonyi wrote:
> 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.

I think that the comment refers to this:

	http://wiki.squeak.org/squeak/3716
	http://wiki.squeak.org/squeak/2119
	http://wiki.squeak.org/squeak/750

I note that the original project estimated completion date is listed as
December 1, 1999. Who among us has never made that mistake ;-)

Dave