When starting a new KMM application, I ran into a crash on iOS that I’m trying to make some sense of. The error message is:

Uncaught Kotlin exception: kotlin.native.concurrent.FreezingException: freezing of com.ramseysolutions.proportalspike.shared.Globals.Companion@f13308 has failed, first blocker is HttpClient[io.ktor.client.engine.ios.IosClientEngine@f13488]

The offending code was:

kotlin

val json = kotlinx.serialization.json.Json { ignoreUnknownKeys = true }
fun createHttpClient() = HttpClient() {
    install(JsonFeature) {
        serializer = KotlinxSerializer(json)
    }
}


class Globals {
    companion object {
        client = createHttpClient()
    }
}

The iOS application utilizes that client in its first view. I noticed in my debugging, that the breakpoints in my iOS project were never getting hit. So I determined the crash was happening before the class that was referencing

client

was ever created. Working that theory, I was able to stop the crash from occurring and achieve the correct results on iOS and Android by removing that

client

property from the

companion object

and by creating a global variable in the iOS project:

// Kotlin Shared

class Globals {
    client = createHttpClient()
}

// iOS
let globals = Globals()

After resolving that, I asserted that a simple global variable would fail also, and I was correct when I tested that. My questions are: what was causing the failure? Are Coroutines unavailable until a certain point in the iOS application lifecycle? And what resources or tools can I use to figure that type of thing out on my own?

Seems like this is a known issue, have a similar issue, have been looking for days and finally found this https://github.com/ktorio/ktor/issues/1550 people are reporting that reverting from ktor

1.4.0

to

1.3.2-1.4.0-rc

works just fine

httpClient

is not getting frozen anymore.

The failure I’m getting was that it failed to freeze the client when initialized as a static/global property, But I get success when it’s not. I’m newer to the Kotlin freezing thing, but it seems to be working to me… But I would like to know how you’re checking if the freezes are successful or not. What tools do you use to inspect that?

I use the good old "_*run it and see if it breaks*_" method. So far I've only worried about freezing on the iOS side when something cracks. Buuut I did noticed that the guys at Touchlab created a library to avoid the freezing, not sure how successful that was. This is their sample project and the library they use for this is

co.touchlab:stately-common:1.1.0

I got the same exception and tried to downgrade ktor as suggested, but it did not help. I found out that I had an

object

with the httpClient as a variable and that the object was not marked as

@ThreadLocal

. Annotating the object fixed my issues. I also had problems upgrading to kotlin 1.4 with the ios project using the Firebase Performance pod. Remove this resolved my issues.