I'm trying to write code which maps some Kotlin va...

# kotlin-native

[r4zzz4k]

I'm trying to write code which maps some Kotlin values into cinteropped ones, and stumbled upon this one trying to process array (for primitives copying values via output.pointed.value = input, for structures I was going to copy bytes and needed size of generic CVariable).
The stuff that breaks:

import kotlinx.cinterop.*

inline fun <reified T : CVariable> sizeOf(value: T) = sizeOf<T>()

fun process(value: Any) {
	when (value) {
		is Int -> 4
		is CVariable -> sizeOf(value)
	}
}

fun main() = Unit

The error:

error: compilation failed: native variable class deserialized class CVariable must have the companion object

 * Source files: sample.kt
 * Compiler version info: Konan: 0.9.1 / Kotlin: 1.3.0
 * Output kind: PROGRAM

exception: java.lang.IllegalStateException: native variable class deserialized class CVariable must have the companion object

[svyatoslav.scherbina]

This code works exactly as it should, because CVariable class doesn’t have any particular size.

[svyatoslav.scherbina]

Btw, what prevents you from using CValue<*> for structs?

[r4zzz4k]

Oh, I completely missed the fact that Type is present, but is not a companion in these abstract classes. Of course it's logical.
Regarding CValue<T> -- I've forgot about it as I only saw it in function signatures and not entirely understood the idea behind it.

Right now I'm preparing List of `GValue: CStructVar`s, allocated within memScoped block, and in the other place getting them from list and trying to convert the list into void*. Should I use CValue<GValue> in the first place instead?

[svyatoslav.scherbina]

Should I use CValue<GValue> in the first place instead?

Yes, I suppose so. This may seem a bit inconvenient, but CValue<GValue> corresponds to the value of the structure (which doesn’t depend on any native memory and remains valid after leaving memScoped {}), while GValue is much like a pointer.
For example, CValue<IntVar> is mostly equivalent to Int.

[r4zzz4k]

I see. And in my function similar to process above I should be able to check is CValue<*> and will have .size handy. Cool, thanks, will try!