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[CLJ-1285] Persistent assoc/conj on a transient-created collision node Created: 28/Oct/13  Updated: 11/Nov/13  Resolved: 11/Nov/13

Status: Closed
Project: Clojure
Component/s: None
Affects Version/s: Release 1.5
Fix Version/s: Release 1.6

Type: Defect Priority: Critical
Reporter: Christophe Grand Assignee: Unassigned
Resolution: Completed Votes: 4
Labels: transient

Attachments: File persistent-assoc-after-collision.diff     File transient-generative-test.diff    
Patch: Code and Test
Approval: Ok


Bug reported by Zach Tellman https://groups.google.com/d/msg/clojure-dev/HvppNjEH5Qc/1wZ-6qE7nWgJ

Since transients were introduced the invariant array.length == count*2 doesn't hold for HashCollisionNode.
However persistent .without still relies on it.

Hence persistent dissoc on a collision node created by transients fails.

(let [a (reify Object (hashCode [_] 42))
      b (reify Object (hashCode [_] 42))]
      (= (-> #{a b} transient (disj! a) persistent! (conj a))
       (-> #{a b} transient (disj! a) persistent! (conj a))))

returns false.

Patch: persistent-assoc-after-collision.diff

Generative test patch: transient-generative-test.diff

The generative test reliably reproduces the error. It is simpler than the original test that found the bug but tests a series conj/disj/transient/persistent actions on a set. I've included it separately in case we decide not to apply.

Screened by: Alex Miller

Comment by Michał Marczyk [ 29/Oct/13 9:58 PM ]

I can confirm that the patch works for me. As per our #clojure conversation, I've done the ClojureScript port; see CLJ-648.

Comment by Reid Draper [ 29/Oct/13 11:28 PM ]

I've run Zach's original test, as well as my own simple-check test. Both are passing.

Comment by Alex Miller [ 30/Oct/13 9:33 AM ]

I don't suppose we could get a generative test (prob need to use test.generative which is already included) to test this stuff similar to the original test that found the bug?

Very much hoping to get this into 1.6.

Comment by Andy Fingerhut [ 31/Oct/13 10:52 AM ]

Alex, I suspect clojure-dev would reach a much wider audience for your request than a comment on this ticket, which only has 3 watchers, and I don't think many people besides you and I watch the stream of all ticket state changes as they go by.

Comment by Michał Marczyk [ 01/Nov/13 5:19 AM ]

Just wanted to note that this patch, apart from preventing the hash-based collections from failing Zach's test suite, also makes avl.clj collections pass (now that I've released fixes for the two bugs uncovered by the test suite in avl.clj 0.0.9). This provides some cross-validation, I think.

(The built-in sorted collections pass either way, because they don't support transient ops.)

Also, David Nolen has merged the ClojureScript port of the patch.

Comment by Alex Miller [ 01/Nov/13 7:35 AM ]

I'm going to take a crack at repro with test.generative this morning - wish me luck!

Comment by Alex Miller [ 03/Nov/13 10:40 PM ]

Added a simplified version of a test-generative test and marked screened.

Comment by Alex Miller [ 11/Nov/13 11:17 AM ]

Patch was applied to master for 1.6.

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