kotlinlang #kotlin-native

Is there a file IO library for Kotlin Native that supports Linux and maybe macOS or Windows? I’m writing a CLI program and Kotlin Native may help with improving experience. Should I just stick to JVM for CLI?

napperley

07/11/2021, 11:31 PM

Is it possible to swap the linker (GCC Gold) that Kotlin Native (with Kotlin 1.5.0 onwards) uses for a newer version (also GCC Gold), and if so where is the linker located on a Linux host? Is gold the linker that Kotlin Native uses ( https://stackoverflow.com/questions/3476093/replacing-ld-with-gold-any-experience )? I'm wondering if the new linker used by Kotlin 1.5.0 makes linking significantly faster than Kotlin 1.4.31; are there any benchmarks available? From experience linking takes up about two thirds of the build time (painfully SLOW!) for a Kotlin Native program.

martmists

07/12/2021, 9:04 AM

Is it possible to have an AtomicReference to a list? I'm getting this error:

Uncaught Kotlin exception: kotlin.native.concurrent.InvalidMutabilityException: mutation attempt of frozen kotlin.collections.ArrayList@1aa3f68
    at kfun:kotlin.Throwable#<init>(kotlin.String?){} (0x4169a9)
    at kfun:kotlin.Exception#<init>(kotlin.String?){} (0x410c87)
    at kfun:kotlin.RuntimeException#<init>(kotlin.String?){} (0x410d97)
    at kfun:kotlin.native.concurrent.InvalidMutabilityException#<init>(kotlin.String){} (0x433557)
    at ThrowInvalidMutabilityException (0x434a76)
    at Kotlin_AtomicReference_checkIfFrozen (0x523c71)
    at kfun:kotlin.native.concurrent.AtomicReference#<init>(1:0){} (0x4328ae)
    at ...

MJegorovas

07/12/2021, 9:30 AM

Anybody could help me converting this obj-c code to kotlin (in thread):

y9san9

07/12/2021, 2:20 PM

Hello mates, while using Kotlin Multiplatform I came across a following issue in Swift. In kotlin we have awesome feature like

Nothing

type, I was trynna use it with generics in entity like

Either

sealed interface Either<out TLeft, out TRight> {
    class Failure<T>(...) : Either<T, Nothing>
    class Success<T>(...) : Result<Nothing, T>
    
}

This is cool approach in Kotlin and everything works fine:

val result: Either<Entity, Error> = result as Success<Entity>

BUT in swift I can't do stuff like this:

guard let result: Either<Entity, Error> = result as? Success<Entity> else { return }

This will break at runtime, since swift generics aren't erased, and it won't pass type check (

Nothing

Error

). Any ideas how to workaround it? cc @alex009

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napperley

07/12/2021, 11:22 PM

In a Kotlin Multiplatform project that is targeting linuxArm32Hfp if Kotlin 1.5.0 or later is used then a boatload of undefined reference errors appear (at the linking stage), eg:

/home/napperley/.konan/dependencies/arm-unknown-linux-gnueabihf-gcc-8.3.0-glibc-2.19-kernel-4.9-2/arm-unknown-linux-gnueabihf/bin/ld.bfd: /mnt/pi_image/usr/lib/arm-linux-gnueabihf/libgdk-3.so: undefined reference to `wl_display_dispatch_pending'

However if Kotlin 1.4.31 is used then none of the errors appear, and the build is successful. In the build output there are a boatload of warnings about missing libraries (at the linking stage) if Kotlin 1.5.0 or later is used, eg:

/home/napperley/.konan/dependencies/arm-unknown-linux-gnueabihf-gcc-8.3.0-glibc-2.19-kernel-4.9-2/arm-unknown-linux-gnueabihf/bin/ld.bfd: warning: libpcre.so.3, needed by /mnt/pi_image/usr/lib/arm-linux-gnueabihf/libglib-2.0.so, not found (try using -rpath or -rpath-link)

Are there some additional linking options that need to be passed to the linker to resolve the errors, and if so which ones?

napperley

07/12/2021, 11:37 PM

There is a lack of documentation on the linking process when developing a Kotlin Native program. No information is present on the linker used in Kotlin 1.5.0 onwards for example. What would happen if someone wants to use a newer linker to resolve GLIBC version issues?

Matthias Geisler

07/14/2021, 7:56 AM

Does anybody has experience with SwiftCrypto usage with Kotlin? I am asking since I am in need of crypto and to do it with objective-c interop looks super error prone.

Iaroslav Postovalov

07/15/2021, 3:13 PM

Hello! I'm experiencing a very bizarre error with Kotlin/Native with

mingwX64

. My test process fails with

-1073741515

exit code and no output. When I've opened the

test.exe

binary with Dependency Walker, it gave out that binary can't be linked with some Microsoft binaries.

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Iaroslav Postovalov

07/15/2021, 5:10 PM

OK, now my problem is that

ld

successfully links against

.lib

file, but as the result

.dll

is lost, and the executable can't find it

Iaroslav Postovalov

07/16/2021, 7:59 AM

How to disable compilation of Native target but still have it in metadata?

itnoles

07/17/2021, 2:45 PM

suspend fun fetch() : HttpResponse = suspendCoroutine {
    val semaphore = dispatch_semaphore_create(0)
    val nativeRequest = NSMutableURLRequest(uRL = NSURL.URLWithString("<https://api.spacexdata.com/v4/launches>")!!)
    nativeRequest.setHTTPMethod("GET")
    val result = AtomicReference(HttpResponse().freeze())
    val completionHandler = { nsData: NSData?, nsURLResponse: NSURLResponse?, nsError: NSError? ->
        if (nsError != null) {
            val message =
                "The response is: " + nsURLResponse?.description() + ", error is: " + nsError.description()
            println(message)
        }
        val response = nsURLResponse as NSHTTPURLResponse
        val httpResponse = HttpResponse().apply {
            statusCode = response.statusCode.toInt()
            body = nsData?.bytes?.reinterpret<ByteVar>()?.toKString()
        }.freeze()
        result.value = httpResponse
        dispatch_semaphore_signal(semaphore)
        Unit
    }.freeze()
    val task =
        NSURLSession.sharedSession.dataTaskWithRequest(nativeRequest, completionHandler)
    task.resume()
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER)
    it.resume(result.value)
}

I really want to simplified this code. Can anyone help me with it?

Big Chungus

07/17/2021, 10:43 PM

If i build target C lib for cinterops on windows with Visual Studio CMAKE, is it expected to work? Or must i build target C libs on MSYS2/CYGWIN to make them "consumable" by K/N? Currently I'm getting this error when compiling kotlin executable on windows, while it works fine on OSX and Ubuntu

Type mismatch: inferred type is bool /* = Byte */ but Boolean was expected

Big Chungus

07/18/2021, 5:07 PM

Trying to run a simple test on mingwX64 and getting this weird error

Cause: cannot assign instance of java.util.Collections$EmptyList to field java.lang.StackTraceElement.moduleVersion of type java.lang.String in instance of java.lang.StackTraceElement

The test

import kotlin.test.Test
import kotlin.test.assertEquals

class TestMe {
   @Test
   fun shouldTest(){
      assertEquals("test", "test");
   }
}

Any pointers?

吴少滨

07/21/2021, 3:51 AM

I need to pass the data model to C++ from Kotlin Native. My current solution is serialization and deserialization through protocol, but as the level of model data increases, it takes more time to transfer the proto method. So I want to find a better solution to replace it. There are some questions about it. 1.Any better suggestions? 2.Now my idea is to create a data model directly in C++. But Kotlin/Native doesn't support C++Interop; Is there any way for Kotlin/Native to get/set the C++ model?

coolcat

07/21/2021, 8:47 PM

Has anyone had any success with the

native.cocoapods

plugin recently? I am trying to write a KMM library whose iOS code depends on a cocoapod, which I import using

cocoapods {
  pod("AFNetworking")
}

However

cinterop

gives me

fatal error: module 'AFNetworking' not found

as in this issue. But I don’t think it’s the same problem. Anyone had similar?

napperley

07/22/2021, 12:54 AM

What does the early version of Kotlin 1.5.30 support in terms of platform code sharing with the C libraries (eg C pointers)?

AJ Alt

07/23/2021, 3:47 PM

With support for Apple Silicon being added in 1.5.30, will you be able to cross compile for the M1 chips from an Intel Mac?

Julius Hannink

07/26/2021, 8:14 AM

Same here, no idea what causes this 😐

@ankushg

any progress on your side?

吴少滨

07/26/2021, 12:07 PM

Is there any documents or demo about Kotlin/Native CInterop for first learning?The official documents can't make me understand. I just touched it not long ago.But CValue、CPointer、CValueVar、CValues and so on that confuses me.I need a simple or detail demo about that.😭

kpgalligan

07/27/2021, 11:59 PM

Curious about "encoding" in

@ObjCMethod

annotation. We've been doing some experiments with cinterop and can successfully link and call to objc methods. As a concrete example, on iOS the objc class for Crashlytics is

FIRCrashlytics

. We only care about getting the global instance and logging a string, so after seeing what cinterop does, we just made this Kotlin class. It'll successfully link to the objc, and calls the methods as we expect.

@ExternalObjCClass
open class FIRCrashlytics : NSObject() {
    @ExternalObjCClass
    companion object : NSObjectMeta(), ObjCClassOf<FIRCrashlytics> {
        @ObjCMethod("crashlytics", "@16@0:8")
        external fun crashlytics(): FIRCrashlytics
    }
    @ObjCMethod(selector = "log:", encoding = "v24@0:8@16")
    open external fun log(msg: String)
}

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Kartik Prakash

07/28/2021, 1:27 AM

Does anyone have a good example a KMP library being published for iOS (Kotlin-Native)? Ideally we want to build a KMP library publish it and consume it in a pure iOS project Obj-C or Swift.

benkuly

07/28/2021, 10:23 AM

Hi, what's the difference between

someByteArray.refTo(0)

and

someByteArray.pinned{it.addressOf(0)}

? Which of them should I use, when I call a native function? And what shoud I do, when the function wants

CValuesRef<uint8_tVar /* = UByteVarOf<uint8_t /* = UByte */> */>

? Is it enough to do

someByteArray.asUByteArray().refTo(0)

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❓ 1

Landry Norris

07/28/2021, 2:45 PM

I noticed that I can't find SwiftUI in the platform package. Is there a timeline on when SwiftUI will be available in iosMain? I'm trying to get an expect/actual for state to use for SwiftUI/Compose. I'd like to be able to use the expect/actual to create the state variables in shared code. This works for Compose, but I can't get the iOS side working without a platform.SwiftUI

Matthias Geisler

07/29/2021, 6:12 PM

Are there any special moves besides obvious things to make the linker faster for iOS?

napperley

07/30/2021, 3:13 AM

I am trying to use the

cairo_region_create_rectangles

function ( https://www.cairographics.org/manual/cairo-Regions.html#cairo-region-create-rectangles ) from the Cairo library, but the function is after

CValuesRef<cairo_rectangle_int_t>?

as the first parameter and I don't know how to provide a

CValuesRef

that contains multiple struct pointers. Below is the code that fails to compile (the values variable doesn't match what the

cairo_region_create_rectangles function

is expecting):

// ...
fun createWithMultipleRectangles(vararg rectangles: IntRectangle): Region {
            val tmpArr = rectangles.map { it.cairoRect.ptr }.toTypedArray()
            val values = cValuesOf(*tmpArr)
            return Region(cairo_region_create_rectangles(values, rectangles.size))
        }
// ...

Tristan

07/30/2021, 8:31 PM

Hello, I have a class in Kotlin with methods such as

class MyClass {
    private val arrayQueue = ArrayQueue<String>()

    fun save(item: String) {
        arrayQueue.add(item);
    }

    val last: String
        get() = arrayQueue.last()
}

I use it in objective C

+ (instancetype)sharedInstance {
    static NativeClass *nativeClass = nil;
    static dispatch_once_t onceToken;

    dispatch_once(&onceToken, ^{
        nativeClass = [[NativeClass alloc] init];
        nativeClass.myClass = [[MyClass alloc] init];
    });

    return nativeClass;
}

First of all, accessing it was an issue just to get

.last

, so I created a wrapper to get a frozen version.

fun getMyClass() = MyClass().freeze()

But by doing this, I cannot mutate it anymore kotlin.native.concurrent.InvalidMutabilityException: mutation attempt of frozen
How can I overcome this kind of issue?

iamsteveholmes

07/30/2021, 8:40 PM

Does anyone know how to upgrade to the latest App structure instead of AppDelegate and SceneDelegate? Asked this on #multiplatform https://kotlinlang.slack.com/archives/C3PQML5NU/p1627586038107100

Landry Norris

08/02/2021, 3:28 PM

Is there anywhere to track the progress of the new GC system? Freezing tends to interfere with other thread-safe methodologies (as the original article on freezing suggests), so the fact that the K/N team suggested that the new GC will not require freezing is helpful. In May, they estimated a dev preview would be available by end of Summer, which is getting close.

Title

Landry Norris

08/02/2021, 3:28 PM

russhwolf

08/02/2021, 3:46 PM

It's not documented but you can try it out in 1.5.30-M1. Need to pass

-memory-model experimental

as compiler args

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Landry Norris

08/02/2021, 3:47 PM

Thank you. I'll try this out. Do you happen to know where you found out about this arg? I'd like to be able to track the progress of this.

russhwolf

08/02/2021, 3:50 PM

If you want to watch a ticket, I don't know anything better than the roadmap at https://youtrack.jetbrains.com/issue/KT-42296 which doesn't go into detail. I found the flag from a mention in a coroutines issue somewhere. I expect we'll hear more about it closer to 1.5.30 release but we'll see

You might also need

kotlin.native.cacheKind=none

in gradle.properties

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