On Sat, Jan 16, 2010 at 12:33 PM, Nicolas Cellier < nicolas.cellier.aka.nice@gmail.com> wrote:
I wrote this test pre-closure. The problem with closures is that they are optimized to retain a pointer to the values of outer temporary variable they use when activated.
Not exactly.
Thus the BlockClosures forAnyTwoEqualObjects ofDifferentIdentity registeringAnActionAtFinalizationForEachObject all refer to 'hello' pointed by o1 and its copy pointed by o2. In other words, o1 and o2 are not the single pointers to the String 'hello' and its copy.
They are. See below.
thenForcingFinalizationOfObjects only clean o1 and o2, but omit to clean the closures that still point to 'hello'... Thus, 'hello' is not finalized. One possibility is to also clean the closures pointing to 'hello'. But now the code is tricky... It's aim was to be simple damned :)
There are single pointers to o1 and o2 from all the code in the test. o1 and o2 are stored in an indirect temp vector array created at the start of the method. The compiler puts them there because there is an assignment to each after they are closed over: o1 := o2 := nil. Smalltalk garbageCollect]. All the blocks that reference o1 or o2 actually reference the indirect temp vector, so there is only one reference to o1 and o2 from all code in the method, though a single indirect temp vector. So as soon as o1 := o2 := nil. is executed the only references to o1 & o2 from code have been deleted.
Nicolas
here is a corrected version :
testFinalizationOfEquals "self debug: #testFinalizationOfEquals"
| finalizationProbe o1 o2 forAnyTwoEqualObjects ofDifferentIdentity registeringAnActionAtFinalizationForEachObject thenForcingFinalizationOfObjects implyBothRegisteredActionsAreExecuted |
finalizationProbe := Set new. o1 := 'hello' copy. o2 := 'hello' copy. forAnyTwoEqualObjects := [o1 = o2]. ofDifferentIdentity := [o1 ~~ o2]. registeringAnActionAtFinalizationForEachObject := [ o1 toFinalizeSend: #add: to: finalizationProbe with: 'first object finalized'. o2 toFinalizeSend: #add: to: finalizationProbe with: 'second object finalized']. thenForcingFinalizationOfObjects := [ forAnyTwoEqualObjects := ofDifferentIdentity := registeringAnActionAtFinalizationForEachObject := nil. o1 := o2 := nil. Smalltalk garbageCollect]. implyBothRegisteredActionsAreExecuted := [finalizationProbe size = 2].
self assert: forAnyTwoEqualObjects; assert: ofDifferentIdentity; should: [ registeringAnActionAtFinalizationForEachObject value. thenForcingFinalizationOfObjects value. implyBothRegisteredActionsAreExecuted value].
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