[Webkit-unassigned] [Bug 145433] New: JavaScriptCore Garbage Collector Issue

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=145433

            Bug ID: 145433
           Summary: JavaScriptCore Garbage Collector Issue
    Classification: Unclassified
           Product: WebKit
           Version: 420+
          Hardware: iOS
                OS: iOS 8.2
            Status: NEW
          Severity: Major
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: maxh at fs.cs.hm.edu

Hello,

Geoffrey Garen advised me to report my following problem here, as it seems to be a bug in JavaScriptCore.

I implemented a JavaScript library for a Swift iOS app connecting via JavaScriptCore. Although I don’t really know if this mail list is the correct place to ask, I thought I’d give it a shot.
I really liked how easy it was to get Swift to work with JavaScript and vice versa. But I stumbled upon a problem when I was testing the performance of my app. I wrote a XCTest in Xcode which performs multiple calls of the JavaScript library (with loops) but it always stops or freezes after the 292nd call.
I guess that the JavaScriptCore context (or virtual machine) is not deinitialized after the method call was successful. I even tried a manual deinitialize (or is deallocate the better word?) but it still freezes. I looked up the allocations and threads in Instruments and it shows multiple VM: JS garbage collector allocations which are still active in the app.
I wrote a question on StackOverflow with some code examples and the Instruments log:
http://stackoverflow.com/questions/30443993/javascriptcore-on-ios-vm-garbage-collector-not-automatically-emtpying
but I haven’t received a single answer yet. I guess JavaScriptCore on iOS is still something that is not being used very much.
I was able to reproduce the issue in another project which I added as a zip file to this report. Just open the project and test or profile it. The loop in the test class will freeze the app after the 292nd call.

I would be very happy if someone could take a look into my problem and share thoughts on it. This is part of my bachelor thesis so it would really help a lot.

Thank you very much in advance and best regards,
Max Hentschel

p.s.: I am using iOS 8.3 but it wasn't selectable from the dropdown. And I cannot tell the version of JavaScriptCore as I wasn't able to find out which version iOS 8.3 uses (no note on Apple's Developer page as well).

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