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ParTrieMap iteration fails with ClassCastException #7498

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scabug opened this issue May 20, 2013 · 7 comments
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ParTrieMap iteration fails with ClassCastException #7498

scabug opened this issue May 20, 2013 · 7 comments
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@scabug
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scabug commented May 20, 2013

Performing a foreach on a ParTrieMap instance sometimes causes the following ClassCastException to be thrown:

java.lang.ClassCastException: scala.collection.LinearSeqLike$$anon$1 cannot be cast to scala.collection.parallel.IterableSplitter
        at scala.collection.parallel.IterableSplitter$$anonfun$splitWithSignalling$1.apply(RemainsIterator.scala:398)
        at scala.collection.immutable.List.foreach(List.scala:309)
        at scala.collection.parallel.IterableSplitter$class.splitWithSignalling(RemainsIterator.scala:398)
        at scala.collection.parallel.mutable.ParTrieMapSplitter.splitWithSignalling(ParTrieMap.scala:123)
        at scala.collection.parallel.ParIterableLike$Accessor$class.split(ParIterableLike.scala:905)
        at scala.collection.parallel.ParIterableLike$Foreach.split(ParIterableLike.scala:972)
        at scala.collection.parallel.AdaptiveWorkStealingForkJoinTasks$WrappedTask.split(Tasks.scala:516)
        at scala.collection.parallel.AdaptiveWorkStealingTasks$WrappedTask$class.spawnSubtasks(Tasks.scala:197)
        at scala.collection.parallel.AdaptiveWorkStealingForkJoinTasks$WrappedTask.spawnSubtasks(Tasks.scala:514)
        at scala.collection.parallel.AdaptiveWorkStealingTasks$WrappedTask$class.internal(Tasks.scala:170)
        at scala.collection.parallel.AdaptiveWorkStealingForkJoinTasks$WrappedTask.internal(Tasks.scala:514)
        at scala.collection.parallel.AdaptiveWorkStealingTasks$WrappedTask$class.compute(Tasks.scala:162)
        at scala.collection.parallel.AdaptiveWorkStealingForkJoinTasks$WrappedTask.compute(Tasks.scala:514)
        at scala.concurrent.forkjoin.RecursiveAction.exec(RecursiveAction.java:160)
        at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:262)
        at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runSubtask(ForkJoinPool.java:994)
        at scala.concurrent.forkjoin.ForkJoinPool.tryHelpStealer(ForkJoinPool.java:1702)
        at scala.concurrent.forkjoin.ForkJoinPool.awaitJoin(ForkJoinPool.java:1830)
        at scala.concurrent.forkjoin.ForkJoinTask.doJoin(ForkJoinTask.java:344)
        at scala.concurrent.forkjoin.ForkJoinTask.join(ForkJoinTask.java:648)
        at scala.collection.parallel.ForkJoinTasks$WrappedTask$class.sync(Tasks.scala:444)
        at scala.collection.parallel.AdaptiveWorkStealingForkJoinTasks$WrappedTask.sync(Tasks.scala:514)
        at scala.collection.parallel.AdaptiveWorkStealingTasks$WrappedTask$class.internal(Tasks.scala:187)
        at scala.collection.parallel.AdaptiveWorkStealingForkJoinTasks$WrappedTask.internal(Tasks.scala:514)
        at scala.collection.parallel.AdaptiveWorkStealingTasks$WrappedTask$class.compute(Tasks.scala:162)
        at scala.collection.parallel.AdaptiveWorkStealingForkJoinTasks$WrappedTask.compute(Tasks.scala:514)
        at scala.concurrent.forkjoin.RecursiveAction.exec(RecursiveAction.java:160)
        at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:262)
        at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:975)
        at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1478)
        at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:104)
@scabug
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scabug commented May 20, 2013

Imported From: https://issues.scala-lang.org/browse/SI-7498?orig=1
Reporter: William Robertson (nullptr)
Affected Versions: 2.10.1
Other Milestones: 2.11.0-M4

@scabug
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scabug commented May 22, 2013

William Robertson (nullptr) said:
I did some instrumentation of the code for ParTrieMap, and it looks like subiter can refer to a TrieMap iterator rather than a ParTrieMap iterator (see around TrieMap.scala:1018 in 2.10.1). A possible fix would be to make sure that subiter is always assigned the result of newIterator which is overloaded in ParTrieMap, although I'm not familiar enough with the codebase to know whether that's the right solution.

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scabug commented May 30, 2013

@retronym said:
Alex: could you please take a look at this one?

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scabug commented May 30, 2013

@axel22 said:
Sure. William's analysis is correct - this is due to a cast in the ParTrieMap of the return value of subdivide from TrieMap, that internally does not call newIterator when it deals with LNodes. I will fix this.

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scabug commented May 30, 2013

@axel22 said:
Should do the trick:

scala/scala#2610

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scabug commented May 30, 2013

@JamesIry said:
Pull request hasn't been merged. We'll close when it has.

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scabug commented Jun 9, 2013

@retronym said:
Reopening for the backport for 2.10.3

scala/scala#2644

@scabug scabug closed this as completed Jul 10, 2013
@scabug scabug added the blocker label Apr 7, 2017
@scabug scabug added this to the 2.10.3-RC1 milestone Apr 7, 2017
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