On Thu, Jul 03, 2008 at 05:44:15PM +0200, Bert Freudenberg wrote:
Am 03.07.2008 um 17:40 schrieb Randal L. Schwartz:
> "Bert" == Bert Freudenberg bert@freudenbergs.de writes:
Bert> Smalltalk does not work that way. If the class format changed, all Bert> existing instance are bulk-migrated to the new class (by creating new Bert> instances and doing a forward-become on all of them).
Well, so this *is* the newbies list... I can *ask*... :)
When does "anObsoleteFooClass" show up then? I know there are checks for it, and I think I made one once. When does that happen? I could probably investigate it myself, but maybe someone can answer this and save me a half hour of poking around.
When the new class is made, the old class is made obsolete. Pointers to the old class coming from Smalltalk, the superclass, and the subclasses are updated. Instances are migrated. After that, the obsolete class will be garbage collected, unless there are pointers to it from other places. These "other places" the class is held can vary wildly:
- Literal references from methods (when the class referenced directly as a global). "SmalltalkImage current fixObsoleteReferences" fixes these. - Various registration services, including, but not limited to: - TheWorldMenu - Flaps - FileList - SystemChangeNotifier - Random caches that are not careful enough. I fixed 3 or 4 cache bugs in Monticello that caused obsolete classes to stick around unnecessarily