How to access a method - Kotlin Shared DLL using CPointer

[dickensas]

Following this Documentation

https://kotlinlang.org/docs/tutorials/native/dynamic-libraries.html

This is a C code in that documentation

 libnative_ExportedSymbols* lib = libnative_symbols();
 lib->kotlin.root.example.forIntegers()

How to do the same in Kotlin

memScoped {
    val lib = alloc<libnative_ExportedSymbols>().apply {
         libnative_symbols()
    }
    println(lib.kotlin.root.example.forIntegers())
}

The lib.kotlin.root.example is perfect but after that how to proceed

I am getting this error

 Type mismatch: inferred type is COpaquePointer? /* = CPointer<out CPointed>? */ but CPointer<CFunction<() -> String>> was expected

[artdfel]

Hello, @dickensas! First of all, I got to remind you about Kotlin/Native issue tracker migration(see #4079). This particular problem seems to be more likely a question rather than a bug, so maybe it could be asked on the #kotlin-native slack channel.
About the error itself. The void * construction from C is being mapped to the special COpaquePointer type(see details here). As the documentation says, such pointer should be explicitly cast to necessary type using .reinterpret() method. In this case, it should look somehow like this:

memScoped {
    val lib = alloc<libnative_ExportedSymbols>().apply {
         libnative_symbols()
    }
    println(lib.kotlin.root.example.forIntegers.reinterpret<<CFunction<() -> String>>().invoke())
}

Also, I just want to ask about reasons of choosing such uneasy approach. Using a .klib might be more relevant here, or I'm missing something?

[dickensas]

I did definitely referred the code for libcurl and curl and understood in the past

The reason I am going for direct DLL is that I am trying create .pyd for python without a C stub

Documentation Reference - .dll -> .pyd

Regarding your code, I could not compile it in kotlin 1.3.72

Therefore I went for this code, Above main method I declared typealias

  typealias SomeFun = CFunction<() -> CPointer<ByteVar>?>
  ....
  ....
  val s = lib.kotlin.root.example.someLibraryMethod?.reinterpret<SomeFun>()    
  println(s?.invoke())

But I am getting null

This is the GitHub URL Kotlin DLL - to - Kotlin

[dickensas]

This technique is working, therefore I close this issue

memScoped {
     val lib:CPointer<libmyext_ExportedSymbols>? = libmyext_symbols()
     println(lib!!.pointed.kotlin.root.example.getHello!!.reinterpret<SomeFun>()!!()!!.toKString())
}

Output

> Task :runDebugExecutableLibpymyext
That is from Kolin DLL

BUILD SUCCESSFUL in 9s