I want to make a list of string pointers within a NativePlacement, but `createValues()` is creating ...

# kotlin-native

[Adam S]

I want to make a list of string pointers within a NativePlacement, but createValues() is creating an CValues with size 24 instead of 3.

Is there a way to create CValues with a specific size?

import kotlinx.cinterop.*

fun main() {
  nativeHeap.cValuesOf(listOf("1", "2", "3"))
}

typealias StringPointer = CPointerVarOf<CPointer<ByteVar>>

fun NativePlacement.cValuesOf(strings: List<String>): CValues<StringPointer> {
  println("strings.size ${strings.size}")
  val array = createValues<StringPointer>(strings.size) { i ->
    val str = strings[i].cstr
    val arr = allocArray<ByteVar>(str.size)
    str.place(arr)
  }
  println("strings array.size ${array.size}")
  return array
}

prints:

strings.size 3
strings array.size 24

[Oleg Yukhnevich]

If you will follow the long chain of functions, you will see, that when creating it via createValues,
array.size returns amount of bytes in CValues - in this case you create CValues where there are 3 pointers (each of 8 bytes)
What do you need this for?

[Oleg Yukhnevich]

Also, BTW, you are not using receiver of createValues at all, so probably in the end it will be anyway empty ^_^

[Adam S]

I need to pass a list of strings into this C function:

int ListView(const char **text, int count);

[Adam S]

the generated Kotlin binding is

public expect fun GuiListViewEx(text: CValuesRef<CPointerVar<ByteVar>>?, count: Int): Int { /* compiled code */ }

[Adam S]

you are not using receiver of

Ahh yes, good spot. I assumed it would be a builder like List(5) { i -> ...}

[Oleg Yukhnevich]

most likely this is what you are looking for: https://github.com/whyoleg/ffi-kotlin/blob/2c78adb60984f38f10db0cccd5a3e01d4f8f575[…]ng/cx/compiler/src/nativeMain/kotlin/clang/CXTranslationUnit.kt
simply allocArray(strings.size) { value = strings[it].cstr.ptr }
most likely last ptr need to be replaced with .getPointer(this) because you need NativePlacement but .ptr declared in MemScope

[Adam S]

allocArray() returns CArrayPointer<>, but I need CValues<>

[Adam S]

oh, no? I've confused myself

[Oleg Yukhnevich]

You need CValuesRef - CPointer extends it

[Adam S]

yup, that's got it working! Thanks Oleg