Throw an exception inside coroutine launched with Dispatchers.Default doesn't crash the app

[romanandreyvich]

I throw an exception inside coroutine launched with Dispatchers.Default and it doesn't crash the app (just print stack trace in console). Works fine if I use Dispatchers.Main instead of Dispatchers.Default.

Here is an example project: https://drive.google.com/file/d/1NzwMU7QStgQuKBNgty1HZei1ZZvQG5Ys/view?usp=sharing

Kotlin: 1.4.20-RC
Coroutines: 1.3.9-native-mt
iOS: 14.1 (iPhone 11, simulator)

[Thomas-Vos]

I am running into this issue as well. Exceptions on Dispatchers.Default only print the stack trace but do not crash the app. It seems that an unhandled exception hook that was set using setUnhandledExceptionHook also does not get called. I use that to report exceptions to Firebase, but as it does not get called, that does not work. Because of that it is very hard to fix crashes thrown from Dispatchers.Default. I am currently trying to work around this by using CoroutineExceptionHandler, that appears to be able to catch the exception. Would really appreciate a solution for this issue.

[Daniel-Jacob]

Is this only an issue on native? Has there been any issues on jvm with this?

[slipdef]

@qwwdfsad any update on this issue?

[qwwdfsad]

We'll try to fix it in the upcoming release

[slipdef]

@qwwdfsad any update on this? It looks like a serious issue - exception in coroutine doesn't crash an app as expected in native.

[Thomas-Vos]

Note that setUnhandledExceptionHook does not catch these exceptions. That could be a problem if you would like to log these exceptions to for example Firebase Crashlytics.

I am using the following code as a workaround so exceptions on background threads are also logged to Crashlytics:

@SharedImmutable
private val defaultExceptionHandler = CoroutineExceptionHandler { context, throwable ->
    throwable // TODO: do something with the throwable, for example log it to Firebase Crashlytics
    throw throwable
}

// Somewhere else in your code
fun main() {
    val dispatcher = Dispatchers.Default + defaultExceptionHandler
    GlobalScope.launch(dispatcher) {
        throw IllegalStateException()
    }
}

It would be great if this would be fixed so the app crashes as well.

[qwwdfsad]

Fixed in 1.5.1-native-mt. For an additional explanation of the behaviour see #2804 (comment)

[Thomas-Vos]

Thanks, can confirm all is working correctly now.