iOS Crashlytics crash log shows _hidden even after upload the bitcode dSYM to fabric

Question

I've been investigating the crash in our app for quite a while, and I still can't figure out why Crashlytics cannot symbolicate some of the crashes (3 to be specific). These are actually the current major crashes of the app and we are desperately looking for any hint possible.

Our app has bitcode enabled and opt-in uploading dSYM to Apple. I tried to read through the Crashlytics doc All about Missing dSYMs , manually download the dSYM zip from iTunesConnect, uploaded it to fabric. The "hidden" crash number keeps growing afterwards, and the problem is, we never get a missing dSYM warning in fabric and it's not showing the dSYM missing in the fabric settings page for the app build we are trying to investigate.

The stack trace is like this: Crash stack trace

Any helps and suggestions would be very much appreciated! Thanks!

Answer 1

I can't tell you why the symbolication failed. But from looking at your crash report, a few things come into my mind, maybe they can help you somehow.

The crash happens inside a closure which uses UIWebView somehow. After doing something with javascript, resources are being freed, this is then when the crash happens. You can check the last code called here:

https://github.com/WebKit/webkit/blob/f43689c3ed50cd00bf76d5731983046b988e6efa/Source/WebCore/loader/cache/CachedResource.cpp

Nothing fancy going on there.

My guess is, that input vars of the closure are freed to early. Even if you are blind, without a working symbolication, you could try to find closures initiating JavaScript calls and check for this conditions eg [unowned self] in or similar and try pass them in owned. This could obviously lead to leaking memory, but you can test this before releasing.