http://dev.clojure.org/jira This file is an XML representation of an issue en-us 4.4 649 25-07-2011 http://dev.clojure.org/jira/browse/CLJ-708 Clojure <p>Multi-methods hold onto the head of their arguments when they are invoked. This means that if you invoke a multi-method with a lazy seq that cannot be held in memory all at once, you blow heap.</p> <p>I'm not sure how best to write a test case for this particular issue, since the easiest way to test it is to run the JVM with a small heap and purposely evoke an OutOfMemoryError, so the attached patch has only the code changes. (However, I have verified the fix using a small heap.)</p> <p>This will fix the issue for arities up to 6, for arities &gt;=7 there is a bug in RestFn where it also holds the head of its arguments. If it is desirable to fix that bug as well, then I can submit a patch for it.</p> CLJ-708

Multi-methods hold onto the head of their arguments

Defect Major Closed Completed Stuart Halloway Paul Stadig Sat, 8 Jan 2011 10:02:06 -0600 Fri, 11 Mar 2011 10:21:21 -0600 Fri, 11 Mar 2011 10:21:20 -0600 Release 1.2 Release 1.3 0 2 <p>Any thoughts on this?</p> <p>I agree that no automated test is necessary for this. If you had attached your small-heap script I wouldn't have to write one from scratch to test it though. <img class="emoticon" src="http://dev.clojure.org/jira/images/icons/emoticons/smile.gif" height="20" width="20" align="absmiddle" alt="" border="0"/></p> <p>Rich: two additional questions on this patch, other than just approval:</p> <ol> <li>Do we want another ticket to fix a similar issue in RestFn?</li> <li>Paul also inquired on the dev list about a 1.2.1 release for this fix. I dread the idea of going to point releases. Any suggestions on workarounds for this for people on the 1.2.x line?</li> </ol> <p>RE: a 1.2.1 release</p> <p>This and the Keyword.intern fix both seem to be fixes for bugs that don't affect functionality, that would be worthy of a 1.2.1 release...I don't know if there are others that people would like to see in there.</p> <p>They both also seem rather "trivial" to merge into 1.2. I'm willing to shepherd the release if no one else is interested in it.</p> <p>Patching both this and RestFn in a single go seems best.</p> <p>We should have a discussion about what might constitute a 1.2.1 on the dev list.</p> <p>Here is an updated patch for both multi-methods and RestFn.</p> <p>I have also pushed a project to <a href="http://github.com/pjstadig/blow-heap">http://github.com/pjstadig/blow-heap</a> that has some (gratuitous but automatically generated) tests for every arity combination.</p> <p>There is a bin directory in that project that contains a blow-heap.sh file that can be run. It will call out to leiningen to run the tests, and the project.clj file is configured to start Java with a sufficiently small heap.</p> <p>You can change the dependencies in the project.clj file to clojure 1.2.0, run the script, and see it fail. Then apply the patch to clojure, `mvn clean install`, go back to the blow-heap project and change the project.clj to use clojure 1.3.0 SNAPSHOT, `lein deps`, and rerun the tests to verify. (Whew!)</p> <p>I believe this patch should also apply cleanly to the 1.2.0 branch, since the multi-method and rest-fn classes haven't changed since then, but if that's not the case I can send another rebased patch.</p> <p>The second commit has the windows-line-ending problem. Anybody know how to fix this in an automated way?</p> <p>The same patch as Paul's, with unix line-endings</p> <p>Stuart: See attached patch run through the dos2unix tool</p> <p>tests pass, approach looks fine. I didn't read every line, let mw know if there is some automated test or analysis you think I should do</p> Approval Ok Global Rank Patch Code