Hi! A coroutine causes a FATAL EXCEPTION but does ...

# android

[Martin Nordholts]

Hi! A coroutine causes a FATAL EXCEPTION but does not give any stack trace or clue about what coroutine it is:

01-14 11:40:10.990  4508  4508 E AndroidRuntime: FATAL EXCEPTION: main @coroutine#4
01-14 11:40:10.990  4508  4508 E AndroidRuntime: Process: com.readly.client, PID: 4508

I am running with

System.setProperty(kotlinx.coroutines.DebugKt.DEBUG_PROPERTY_NAME, kotlinx.coroutines.DebugKt.DEBUG_PROPERTY_VALUE_ON)

but still get the above silent fail.

What is the best way to find what coroutine this is? (Without using “brute force”)

[tseisel]

That's rather strange, because on Android the default behavior is to crash the app when a top level coroutine fails.
Begin by checking all coroutines that are launched with GlobalScope , those are the most susceptible to fail silently.

[Martin Nordholts]

The app does crash 💡

Begin by checking all coroutines that are launched with GlobalScope , those are the most susceptible to fail silently.

Thanks for the tip which certainly would work, but I would like to find a way that does not use brute force, because that doesn’t scale well (e.g. to a codebase that has a ton of coroutines)

[tseisel]

What you mean is that the app crashes, but you don't have a full stacktrace describing where and why it failed ?

[Martin Nordholts]

exactly

or more precisely, the why is not that important, but the where is (at the moment)

[tseisel]

One possibility for fast debugging is to install a CoroutineExceptionHandler that will perform the necessary logging (printing a stacktrace) : https://kotlinlang.org/docs/reference/coroutines/exception-handling.html#coroutineexceptionhandler

[Martin Nordholts]

Thanks for the tip, I tried

Thread.setDefaultUncaughtExceptionHandler { t: Thread, e: Throwable ->
            Log.e("foo", "bar", e)
        }

and now I can get a stack trace 👍