On Wed, Nov 26, 2008 at 07:45:14PM -0800, Andreas Raab wrote:
> Secondly, the issue I was seeing with the iVars being incorrect are one 
> of the subtleties that SE currently doesn't correctly deal with. Here is 
> an illustration:
> 
> testCleanupOfOldInstances
>    "Ensure that old instance are cleaned up properly"
>    instance := CleanupTestClass new.
>    Smalltalk garbageCollect. "for easier results make it old"
> 
>    self assert: CleanupTestClass instanceCount = 1.
> 
>    ed := SystemEditor new.
>    (ed at: #CleanupTestClass) addInstVarName: #whatever.
>    ed commit.
> 
>    self assert: CleanupTestClass instanceCount = 1.
> 
>    ed := SystemEditor new.
>    (ed at: #CleanupTestClass) removeInstVarName: #whatever.
>    ed commit.
> 
>    self assert: CleanupTestClass instanceCount = 1.
> 
> The problem is that since #become: changes class pointers you *must* 
> clean out the old instances or otherwise they'll be completely and 
> utterly broken when you finally #become: the classes itself. This can be 
> achieved by placing a strategic full GC in the right place in the 
> migration process (I'm not sure where that would be in SE but probably 
> somewhere in the migration transaction).

You are right. There is no equivalant to the garbageCollect in
ClassBuilder >> migrate:to:. The best place to put it would
probably be at the end of SystemEditor>>commit

-- 
Matthew Fulmer -- http://mtfulmer.wordpress.com/