[native-mt] ClassCastException when executing iOS tests with coroutines

[marekniedbach-silvair]

Hello,
I'm very sorry about the lack of details, but I have failing the unit tests in one of the internal class related to the kotlin coroutines.

When testing the production code that heavy rely on the coroutines (many launch and delay inside), the unit test is sometimes failing. It is not fully reproducible, as it happens only when executing ./gradlew clean check command. When I run the check command (without the clean) again then everything is passing without an issue. What's more weird, not the same test is failing after clean.

The top of the callstack with the exception looks like below:

kotlin.ClassCastException: kotlinx.coroutines.internal.Removed cannot be cast to kotlinx.coroutines.internal.LockFreeLinkedListNode
	at kotlin.Throwable#<init>(/Users/teamcity3/buildAgent/work/c3a91df21e46e2c8/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Throwable.kt:24)
	at kotlin.Exception#<init>(/Users/teamcity3/buildAgent/work/c3a91df21e46e2c8/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Exceptions.kt:23)
	at kotlin.RuntimeException#<init>(/Users/teamcity3/buildAgent/work/c3a91df21e46e2c8/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Exceptions.kt:34)
	at kotlin.ClassCastException#<init>(/Users/teamcity3/buildAgent/work/c3a91df21e46e2c8/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/Exceptions.kt:106)
	at <global>.ThrowClassCastException(/Users/teamcity3/buildAgent/work/c3a91df21e46e2c8/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/native/internal/RuntimeUtils.kt:31)
	at kotlinx.coroutines.internal#unwrap__at__kotlin.Any(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/concurrent/src/internal/LockFreeLinkedList.kt:668)
	at kotlinx.coroutines.JobSupport.notifyCancelling#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/JobSupport.kt:332)
	at kotlinx.coroutines.JobSupport.tryMakeCancelling#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/JobSupport.kt:810)
	at kotlinx.coroutines.JobSupport.makeCancelling#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/JobSupport.kt:766)
	at kotlinx.coroutines.JobSupport#cancelImpl(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/JobSupport.kt:682)
	at kotlinx.coroutines.JobSupport#cancelCoroutine(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/JobSupport.kt:669)
	at kotlinx.coroutines.TimeoutCoroutine.run#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/Timeout.kt:159)
	at kotlinx.coroutines.test.TestDispatcher#processEvent(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestDispatcher.kt:28)
	at kotlinx.coroutines.test.TestCoroutineScheduler.tryRunNextTask#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestCoroutineScheduler.kt:95)
	at kotlinx.coroutines.test.TestCoroutineScheduler#advanceUntilIdle(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestCoroutineScheduler.kt:110)
	at kotlinx.coroutines.test.$runTestCoroutineCOROUTINE$202#invokeSuspend(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestBuilders.kt:212)
	at kotlinx.coroutines.test#runTestCoroutine(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestBuilders.kt:198)
	at kotlinx.coroutines.test.$runTest$<anonymous>_3COROUTINE$203.invokeSuspend#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestBuilders.kt:167)
	at kotlinx.coroutines.test.$runTest$<anonymous>_3COROUTINE$203.invoke#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestBuilders.kt:166)
	at kotlinx.coroutines.test.$createTestResult$lambda-0COROUTINE$208.invokeSuspend#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/native/src/TestBuilders.kt:13)
	at kotlin.coroutines.native.internal.BaseContinuationImpl#resumeWith(/Users/teamcity3/buildAgent/work/c3a91df21e46e2c8/kotlin/kotlin-native/runtime/src/main/kotlin/kotlin/coroutines/ContinuationImpl.kt:30)
	at kotlinx.coroutines.DispatchedTask#run(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/internal/DispatchedTask.kt:106)
	at kotlinx.coroutines.EventLoopImplBase#processNextEvent(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/common/src/EventLoop.common.kt:281)
	at kotlinx.coroutines#runEventLoop(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:87)
	at kotlinx.coroutines.BlockingCoroutine.joinBlocking#internal(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:74)
	at kotlinx.coroutines#runBlocking(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:55)
	at kotlinx.coroutines#runBlocking$default(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-core/native/src/Builders.kt:35)
	at kotlinx.coroutines.test#createTestResult(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/native/src/TestBuilders.kt:12)
	at kotlinx.coroutines.test#runTest__at__kotlinx.coroutines.test.TestScope(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestBuilders.kt:166)
	at kotlinx.coroutines.test#runTest(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestBuilders.kt:154)
	at kotlinx.coroutines.test#runTest$default(/opt/buildAgent/work/44ec6e850d5c63f0/kotlinx-coroutines-test/common/src/TestBuilders.kt:147)

I can't provide the example project as it is hard to understand for me what is happening, and the whole project is a bit complicated.

I have the issue above even If I don't use the kotlinx-coroutines-test library at all - I have a custom implementation of time control with the use of internal api too - so it looks like the issue is more in the coroutines library than the coroutines-test.

Versions:
kotlin-gradle-plugin:1.6.20
kotlinx-coroutines-core:1.6.0-native-mt

[qwwdfsad]

I would suggest migrating to new MM and regular coroutine builds as native-mt is being decommissioned: #462 (comment)

We still ready to fix critical bugs during 1.6.x lifetime, but unfortunately it doesn't seem to be it.

[marekniedbach-silvair]

I've migrated our project to new MM and it works without the mentioned issue 👍