A new version of System was added to project The Inbox:
http://source.squeak.org/inbox/System-cwp.662.mcz

==================== Summary ====================

Name: System-cwp.662
Author: cwp
Time: 12 January 2014, 10:23:54.166 am
UUID: 38c55d98-af64-4c5e-abbf-df86ad07fc7b
Ancestors: System-cwp.661

Remove the marker object from allObjectsDo:, and return to iterating until 0 is encountered. Also, fetch the next object before evaluating the block, to allow the block to use #become: safely.

=============== Diff against System-cwp.661 ===============

Item was changed:
  ----- Method: SystemNavigation>>allObjectsDo: (in category 'query') -----
  allObjectsDo: aBlock 
  	"Evaluate the argument, aBlock, for each object in the system 
+ 	excluding SmallIntegers. New objects created by aBlock will 
+ 	be included in the enumeration, and it is up to the caller to avoid
+ 	creating new objects faster than they are enumerated. It's
+ 	important that the next object is fetched before the block is 
+ 	evaluated, because the block may use #become: to change the
+ 	identity of object."
+ 
+ 	| object nextObject |
- 	excluding SmallIntegers. With closures, this needs to use an end
- 	marker (lastObject) since activation of the block will create new 
- 	contexts and cause an infinite loop."
- 	| object lastObject |
  	object := self someObject.
+ 	[nextObject := object nextObject.
+ 	aBlock value: object.
+ 	object := nextObject.
+ 	0 == nextObject]
+ 		whileFalse.
+ !
- 	lastObject := Object new.
- 	[lastObject == object or: [0 == object]]
- 		whileFalse: [aBlock value: object.
- 			object := object nextObject]!