Fix unlikely but possible race in `WeakValueDictionary`
It may happen that value in `valueArray` could have been already
collected by the GC but #clearDeadSlots have not yet been called.
When this happened, `#at:ifAbsentPut:` returned tombstone rather
than updating the dictionary with value from block.
This commit fixes this by checking whether `valueArray` contain
the tombstone and if so, clearing up the dead slots and restarting
the operation. HTH.
--- a/WeakValueDictionary.st Wed Feb 03 11:52:30 2021 +0000
+++ b/WeakValueDictionary.st Thu Mar 25 20:30:03 2021 +0000
@@ -1,5 +1,6 @@
"
COPYRIGHT (c) 1992 by Claus Gittinger
+ COPYRIGHT (c) 2021 LabWare
All Rights Reserved
This software is furnished under a license and may be used
@@ -25,6 +26,7 @@
copyright
"
COPYRIGHT (c) 1992 by Claus Gittinger
+ COPYRIGHT (c) 2021 LabWare
All Rights Reserved
This software is furnished under a license and may be used
@@ -300,6 +302,38 @@
"Modified: / 13.12.2001 / 14:18:56 / martin"
!
+findKeyOrNilOrDeletedEntry:key
+ | index value |
+
+ (OperatingSystem blockInterrupts) ifFalse:[
+ "/
+ "/ may never be entered with interrupts enabled
+ "/
+ OperatingSystem unblockInterrupts.
+ self error:'unblocked call of findKeyOrNil'.
+ ].
+
+ "/ It may happen that value could have been already
+ "/ collected by the GC but #clearDeadSlots have not yet
+ "/ been called. In that case, valueArray would contain
+ "/ a tombstone (a SmallInteger).
+ "/
+ "/ So, we check whether the value contains tombstone
+ "/ and if so, clear all dead slots and restart.
+ [
+ index := super findKeyOrNilOrDeletedEntry:key.
+ value := valueArray at: index.
+ value class == SmallInteger
+ ] whileTrue: [
+ self clearDeadSlots
+ ].
+ OperatingSystem unblockInterrupts.
+
+ ^ index
+
+ "Created: / 25-03-2021 / 20:03:12 / Jan Vrany <jan.vrany@labware.com>"
+!
+
possiblyShrink
"check if the receiver has become too empty (after a remove)
and shrink if it makes sense.
@@ -384,5 +418,10 @@
version
^ '$Header$'
+!
+
+version_HG
+
+ ^ '$Changeset: <not expanded> $'
! !