Anyone having issues returning a native var (e.g. ...

# kotlin-native

[Hauke Radtki]

Anyone having issues returning a native var (e.g. ULongVar) from a suspending function? Im getting a typecast exception from NativePointed to the return type (ULongVar in this instance). Reproducer inside ⬇️

[Hauke Radtki]

@Test
    fun suspendReturnNativeVar() {
        suspend fun NativePlacement.returnStruct(): ULongVar {
            val buffer = allocArray<UByteVar>(sizeOf<ULongVar>())

            // Any suspending data fetch function
            delay(1)

            val reinterpret = buffer.reinterpret<ULongVar>()
            reinterpret[0] = 0xAAAAu

            return reinterpret.pointed
        }

        runBlocking {
            memScoped {
                val v = returnStruct()

                assertEquals(0xAAAAu, v.value)
            }
        }
    }

[Hauke Radtki]

Im getting a kotlin.ClassCastException: kotlinx.cinterop.NativePointed cannot be cast to kotlinx.cinterop.ULongVarOf when the coroutine returns to the calling context (when coroutine dispatches the assignment of val v)

[Hauke Radtki]

Removing the suspend keyword (and the delay) makes this work

[Hauke Radtki]

Tested on 1.4.35 and 1.5.0 with multithreaded coroutines (though no threading involved here)