Friday, November 7, 2014 [Tweets] [Favorites]

Tracking Down a WebKit Crasher

Daniel Jalkut:

I love it when customers take the time to write something about the circumstances surrounding a crash. Often even a little clue can be enough to lead to the unique series of steps that will ultimately reproduce the problem.

[…]

This is where the open-sourced nature of WebKit is both a blessing and a curse. If this issue had been revealed to exist somewhere deep within AppKit, or any of Apple’s other closed-source frameworks, I most certainly would have thrown up my arms, filed a bug, and hoped for the best. But Apple’s WebKit framework is something I can download, build, and debug. Sure, it takes nearly all day to build, and there is a steep learning curve to debugging it, but why did I become a software developer if I’m not up for a challenge?

[…]

To make a long, long, long, long, story very short: I used Instruments and its “pairing” functionality, which lets you hide balanced pairs of retain/release calls so that you are left with a more manageable subset of calls to examine and scrutinize. After scratching my head over this for hours and not making much headway, I finally came upon a specific call stack that had a very suspicious heritage. I confirmed through Instruments and then by direct examination of WebKit source code, that the WebView instance in question was in fact retaining and then autoreleasing itself as part of its dealloc method.

1 Comment

[…] right way to do things and leads to a higher quality product. It’s incredibly satisfying to track down root causes. But you have to exercise some discretion because this is a hole with no bottom. At a […]

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