kotlinlang #kotlin-native

Hi All. I hope I’m not asking that was asked 1000 times before, but I couldn’t find any reliable answer on the web. We are evaluating using K/N for our new and shiny startup’s standalone client app, which should run on MacOS, Linux & Windows. We have no plans to run this client on iOS/Android. Do you know of any real-world standalone desktop app project that’s using K/N? Is K/N suitable for this you think or is it mainly a tool for doing KMM right? We will need things like: • desktop notifications • File-system monitoring and • Displaying a React based UI inside a browser wrapper window. EDIT: building Kotlin/JVM is not an option for us, as we’re building a daemon, and the JVP heap requirements is not acceptable for our use-case.

napperley

04/08/2022, 2:04 AM

Today the experimental memory model has been used along with Kotlin 1.6.20 (previously Kotlin 1.4.31 was used) in production with a custom backend service (Linux Daemon). Reserved RAM usage has increased from around 9.8 MB to around 17 MB. Release binary size has slightly decreased from 4.2 MB to 4.1 MB. I'm guessing that the increase in RAM usage comes down to a full GC being used instead of the partial GC used by the old memory model. It should be noted that only changes were made to the build side of the code base (incl build configuration).

🎉 1

🔍 3

Joakim Forslund

04/08/2022, 6:15 AM

Kotlin: 1.6.10 and 1.6.20 MM enabled I have a callback in c looking this:

int (*messageClass)(struct UIElement *element, UIMessage message, int di /* data integer */, void *dp /* data pointer */);

I also have this c function:

UIElement *UIElementCreate(size_t bytes, UIElement *parent, uint32_t flags,

int (*messageClass)(UIElement *, UIMessage, int, void *), const char *cClassName);

That in kotlin interop becomes:

fun UIElementCreate(

bytes: size_t,

parent: CValuesRef<UIElement>?,

flags: uint32_t,

messageClass: CPointer<CFunction<(CPointer<UIElement>?, UIMessage, Int, COpaquePointer?) -> Int>>?, cClassName: kotlin.String?): CPointer<UIElement>? { }

I then try to call above method from kotlin with:

UIElementCreate(sizeOf<UIWindow>().toULong(),null,UI_ELEMENT_WINDOW,staticCFunction(::messageCallback),"Window")

fun messageCallback(element: CPointer<UIElement>?, message: UIMessage, di: Int, dp: COpaquePointer?): Int {

println("Inside weird ass callback")

return 0

This results in a crash, What am I doing wrong? As a side-note I also ran the staticCFunction as inline, had the same result (and the function is called just fine from pure c)

jcechace

04/12/2022, 2:11 PM

Hi… What is the support for databases in kotlin native? E.g. is it possible to use for example Postgres? So far it looks like either there really isn’t any db support (except for maybe sqlite and some mobile databases such as Ream / Firebase) or my Google-fu is weak today.

James Ward

04/15/2022, 10:25 AM

Is there any way to deal with "classpath" resources in Kotlin/Native? In jvm-land I put a properties file with config into

META-INF

and then load it via

classLoader.getResourceAsStream

but I'm not sure if there is a way to do something similar in native.

4brunu

04/19/2022, 9:51 AM

Hi, I'm trying to integrate kermit in my KMM project, but to do that, first I need to convert the KMM iOS XCFramework from dynamic to static. I have done it by doing so

listOf(
        iosX64(),
        iosArm64(),
        //iosSimulatorArm64() sure all ios dependencies support this target
    ).forEach {
        it.binaries.framework {
            baseName = "shared"
            isStatic = true
        }
    }

The problem is that when I make this change, I got 5000 warnings when building the iOS project. Any idea why? By the way, I'm not using cocoapods. ``````

Ayfri

04/22/2022, 11:10 PM

Hi, how can I put a string into a

CPointer<WCHARVar>

Charles Prado

04/26/2022, 6:50 PM

Hi.

Calling Kotlin suspend functions from Swift/Objective-C is currently supported only on main thread

I’m using KTOR 2.0.0 with the new memory model. Getting this error when trying to call an async func inside a Task from this iOS side. There’s currently something I can do to be able to call that function in that context?

Dominaezzz

04/27/2022, 8:29 PM

Anyone seen something like this before?

w: skipping D:\a\kgl\kgl\kgl-glfw\build\classes\kotlin\commonizer\cglfw\H3MydyJqF8c0JoJ3z3gndIlI7DE=\(linux_x64, macos_x64, mingw_x64)\com.kgl_kgl-glfw-cinterop-cglfw. The target doesn't match. Expected 'linux_x64', found [mingw_x64]

https://github.com/JetBrains/kotlin/blob/v1.6.21/kotlin-native/shared/src/library/[…]kotlin/org/jetbrains/kotlin/konan/library/SearchPathResolver.kt

martmists

04/30/2022, 4:13 PM

How do I properly commonize libraries? I've got a setup where each linuxX64Main, mingwX64Main, etc all depend on nativeMain in project A Then in project B, the nativeMain depends on project A, and again all <platform>Main sourcesets depend on nativeMain. It compiles just fine, but IntelliJ doesn't recognize the functions from project A's cinterops in the nativeMain module. (build.gradle.kts for A and B in thread)

napperley

05/02/2022, 9:22 PM

Does Kotlin Native have a module loading system that is similar to what can be found on some platforms ( https://stackoverflow.com/questions/384121/creating-a-module-system-dynamic-loading-in-c )? I would like to develop a Kotlin Native program that has a basic plugin system built in where certain functionality is loaded on demand, without requiring all C libraries to be available on the target platform. For example, one might develop a Kotlin Native program which generates performance reports that come in various types. One of these types is PDF which requires the Cairo library ( https://www.cairographics.org/ ) to be loaded, whereas the Console report just uses the built in platform libraries and doesn't require the Cairo library.

napperley

05/03/2022, 1:05 AM

Was busy looking at a C API ( https://man7.org/linux/man-pages/man7/rtnetlink.7.html ) and wondering if it is a User Space or Kernel Space API. The Man Page description is a bit confusing, "... though this usage is not documented here, and for communication with user-space programs..." ❓ 😕. If it is a User Space API then it should be accessible from the Kotlin side, although it appears this API is macro heavy which complicates matters.

martmists

05/04/2022, 10:53 PM

In terms of performance, is it better to work with a FloatArray or an allocated CArrayPointer<FloatVar>, or is it about equal? edit: did some testing in this thread, tl;dr is that in release binaries K/N is slightly slower than c++ with no optimization flags but still fast enough for realtime tasks

:nice: 1

rrva

05/05/2022, 3:43 PM

If i am writing a multiplatform lib targeting android, ios and js, what is a good solution for multiplatform caching for example the LoadingCache pattern Lets say i have a

suspend fun refreshToken(token: Token)

if the cache is cold, I want to prevent coroutines concurrently refreshing the value I have tried some solutions Semaphore (the coroutine aware one) Actor-like impl with channels but without actor lib. Are there any other simpler/more obvious solutions?

napperley

05/06/2022, 3:46 AM

Which performance metrics should be taken into account with a Kotlin Native program? Below is an example of what my program ( https://gitlab.com/napperley/performance-snapshot ) prints to the console:

./perf_snap.kexe sunny --useSsh remote_host
Creating SSH Console report...
-- sunny Resource Usage --
Short Process Name: sunny_island_te
Binary Path: /home/a_user/sunny_island_telemetry.kexe
Threads Used: 3
Total Reserved RAM (in KB): 24840
Binary Size (in bytes): 4149432

MJegorovas

05/06/2022, 1:45 PM

Is it possible to observe kotlin class properties in swift? Like with

ObservableObject

and

Published

in swiftUI.

Vivek Modi

05/06/2022, 9:38 PM

Hey guys, I just join this channel. Can someone tell me what kind of questions we can ask here. Thanks 👍

martmists

05/06/2022, 10:58 PM

What does this error mean? I'm just redefining some

#define

'd functions into actual functions

Nikolay Kasyanov

05/12/2022, 12:01 PM

Hey folks 👋 I just stumbled upon the fact that

Any?.identityHashCode()

in Native uses object’s memory address only, unlike JVM, where a piece of random data could be used, making

identityHashCode

unique even if two objects happen to be allocated at the same memory address during app’s lifetime. Would it make sense to file this as a bug (it’s a noticeable discrepancy with JVM, after all) or is it a conscious decision to have this implementation in Native?

hfhbd

05/12/2022, 3:27 PM

Does anybody know an alternative for https://www.testcontainers.org? Or "only" a Kotlin native docker library?

👍 1

Simon BRUNOU

05/13/2022, 2:19 PM

Hey all, I was wondering how to import some Win32 APIs in Kotlin/Native. Basically, I need to convert this C call to a Kotlin/Native one, but I can’t seem to understand if those headers are included in

platform.windows.*

platform.posix.*

#include <Winsock2.h>
#include <Ws2bth.h>
#include <BluetoothAPIs.h>

Those are standard Win32 headers but I can’t find them anywhere on Kotlin/Native. I am developing on macOS 12.4 with an M1 processor, if it matters. Do I need to use cinterop and bind them manually? Or am I looking in the wrong place? Thanks in advance!

martmists

05/14/2022, 10:19 AM

Getting an error compiling my code (file in thread)

e: org.jetbrains.kotlin.backend.common.BackendException: Backend Internal error: Exception during IR lowering
      File being compiled: /home/mart/git/kaudio-python/src/nativeMain/kotlin/kaudio/nodes/util/InputNode.kt
      The root cause java.lang.IllegalArgumentException was thrown at: org.jetbrains.kotlin.backend.konan.lower.InteropTransformer.visitCall(InteropLowering.kt:1117)
          at org.jetbrains.kotlin.backend.common.CodegenUtil.reportBackendException(CodegenUtil.kt:238)
          at org.jetbrains.kotlin.backend.common.CodegenUtil.reportBackendException$default(CodegenUtil.kt:234)
          at org.jetbrains.kotlin.backend.common.phaser.PerformByIrFilePhase.invokeSequential(performByIrFile.kt:68)

Ji Sungbin

05/14/2022, 10:21 AM

Hi, why Kotlin does not allow the use named arguments for function types?

martmists

05/14/2022, 10:26 PM

I can't run a gradle build in intellij, I just get this error:

'void com.jetbrains.cidr.execution.debugger.CidrDebuggerSettings.setLLDBNatvisRenderersEnabled(boolean)'

Sam Stone

05/15/2022, 4:00 PM

Does Kotlin native compile to bytecode or c?

Alexander Black

05/16/2022, 7:33 PM

This might not be the right place to ask this, (if so let me know)… I’m wondering if anyone else has experienced an issue with SQLDelight on native incrementing primary keys when doing a

INSERT OR REPLACE INTO (id, ...) VALUES(?, ...)

operation? So if I had a null id passed in for the primary key… it makes sense, but I’m not passing in a null. Any advice would be helpful.

Karel Petránek

05/19/2022, 11:36 PM

I’m trying to implement

AVCaptureVideoDataOutputSampleBufferDelegateProtocol

in Kotlin on iOS and the delegate method never gets called (equivalent code in Swift/ObjC works fine). I suspect it’s because of the protocol definition in Kotlin:

@kotlinx.cinterop.ExternalObjCClass public interface AVCaptureVideoDataOutputSampleBufferDelegateProtocol : platform.darwin.NSObjectProtocol {
    @kotlinx.cinterop.ObjCMethod public open fun captureOutput(output: platform.AVFoundation.AVCaptureOutput, didOutputSampleBuffer: platform.CoreMedia.CMSampleBufferRef? /* = kotlinx.cinterop.CPointer<cnames.structs.opaqueCMSampleBuffer>? */, fromConnection: platform.AVFoundation.AVCaptureConnection): kotlin.Unit { /* compiled code */ }

    @kotlinx.cinterop.ObjCMethod public open fun captureOutput(output: platform.AVFoundation.AVCaptureOutput, didDropSampleBuffer: platform.CoreMedia.CMSampleBufferRef? /* = kotlinx.cinterop.CPointer<cnames.structs.opaqueCMSampleBuffer>? */, fromConnection: platform.AVFoundation.AVCaptureConnection): kotlin.Unit { /* compiled code */ }
}

Note that both

captureOutput

methods have the exact same signature, they only differ in parameter names. It is impossible to override both methods in Kotlin (it’s also impossible to define such interface in Kotlin code) so I suspect some trickery there. Has anyone met this issue before? Is there a workaround to make Kotlin properly override these ObjC methods?

Julian Hille

05/20/2022, 8:52 AM

Hey there, im asking myself if there is a possibility to compile kotlin to objectiv c on linux instead of on macos? So far i did not find any documentation about changing the compiler from c/cpp to objc on the linux target. Is this even possible?

Conrad Kramer

05/23/2022, 8:45 PM

When Kotlin throws an exception in my iOS and macOS app and it is unhandled, the crash report is not super helpful at the moment The stack track is in

Kotlin_ObjCExport_trapOnUndeclaredException

and the “Application Specific Information” which normally contains the exception message (for Swift traps and Objective-C exceptions) just shows

abort() called

Is there a way to put the Kotlin exception message inside of the crash report?

Title

Conrad Kramer

05/23/2022, 8:45 PM

When Kotlin throws an exception in my iOS and macOS app and it is unhandled, the crash report is not super helpful at the moment The stack track is in

Kotlin_ObjCExport_trapOnUndeclaredException

and the “Application Specific Information” which normally contains the exception message (for Swift traps and Objective-C exceptions) just shows

abort() called

Is there a way to put the Kotlin exception message inside of the crash report?

ankushg

05/23/2022, 8:53 PM

We’ve used CrashKiOS for this: https://github.com/touchlab/CrashKiOS I believe it’s also integrated into Kermit?

Rick Clephas

05/23/2022, 8:54 PM

I don't believe there is. If I remember correctly folks at Touchlab actually log the unhandeled exceptions at the Kotlin side in their Kermit library. https://github.com/touchlab/Kermit

Conrad Kramer

05/23/2022, 8:55 PM

There is

setUnhandledExceptionHook

(which is what they use), so perhaps I could take the exception and crash myself in a way that reports the exception message correctly I do wonder how “Application Specific Information” is populated, though, and if there is a way to get this functionality into Kotlin itself

Because other information goes in there, like the “dyld4 config” and the current selector being performed by AppKit if present

Rick Clephas

05/23/2022, 9:00 PM

Yeah. Maybe if you convert the exception to an

NSError

and then send it to ObjC/Swift. From there you could basically throw it or something to get the "normal behavior". Not sure if that would actually work but might be worth to try.

Conrad Kramer

05/23/2022, 9:01 PM

I could generate an NSException and throw it

But thankfully Swift is open source and I am figuring out how they do it: https://github.com/apple/swift/blob/b3b080e12d60a558a2155892e771a98b54a7825a/stdlib/public/runtime/Errors.cpp#L264-L295

:nice: 1

👀 1

Looks like it is private API, but it is a DATA section of the process that Swift fills out before aborting (

__crash_info

)

I’ll write a Kotlin library to populate that in the hook and actually let Kotlin finish the abort

🙌🏻 2

Wireshark, Firefox, etc all have implementations of it: https://github.com/wireshark/wireshark/blob/master/wsutil/crash_info.c

ankushg

05/23/2022, 9:21 PM

Nice, maybe worth checking with @kpgalligan to see if they’d considered adding that to crashkios and ruled it out for some reason

Rick Clephas

05/23/2022, 9:22 PM

Very interesting! Looks like even more info could be attached (like the app specific backtrace).

kpgalligan

05/23/2022, 9:26 PM

Interesting. We haven't done that. Obviously I'd be very interested to see what you come up with. On my phone now but will look at source linked when back on the computer

Conrad Kramer

05/25/2022, 7:42 AM

Funnily enough, Kotlin tries to do it itself, but it looks like the private API they were using may have broken: https://github.com/JetBrains/kotlin/blob/4c3fb8697b0a2b4bb504557427ec309aedffeaac/kotlin-native/runtime/src/main/cpp/ObjCExceptions.cpp#L100

Actually, they don’t enable that for macOS

kpgalligan

05/25/2022, 12:00 PM

That exception writing from the kotlin runtime has been there for years. I don’t know if the api is currently broken, but it used to write to your local device (or the buffer it wrote to wrote to your local device). It never surfaced to remote exception loggers (Crashlytics, etc), which was (is) our goal, so we didn’t try too much with it.

I’ve been poking around this since you posted, so I have some more thoughts (and old things coming back from long term memory).

Crashlytics is aware of the

__crash_info

structure (https://github.com/firebase/firebase-ios-sdk/blob/35669875acdb8d27503feead0d8a2b3d3a0fe19c/Crashlytics/Crashlytics/Components/FIRCLSProcess.c#L752), but it seems to only care about the

message

field (https://github.com/firebase/firebase-ios-sdk/blob/35669875acdb8d27503feead0d8a2b3d3a0fe19c/Crashlytics/Crashlytics/Components/FIRCLSProcess.c#L804). I was getting excited that maybe the

backtrace

field (https://github.com/firebase/firebase-ios-sdk/blob/35669875acdb8d27503feead0d8a2b3d3a0fe19c/Crashlytics/Crashlytics/Components/FIRCLSProcess.c#L756) would be the magic key, but as far as I can see, at least Crashlytics doesn’t care about it.

Now, is it possible that I’m just looking in the wrong place? Absolutely. I’m not sure when I’ll get time to finish it, but I’ve been setting up a little C code to write to those fields and see what comes out, but C isn’t exactly my strong suit, and obviously there isn’t a lot of documentation out there, so we’ll see.

From what I can tell, Crashlytics grabs the state of all threads stacktraces at abort time and writes them out, so for our purposes (full stack trace), I don’t think it’ll work.

My approach prior to this thread was appending the stack info before sending the crash. Bugsnag at least lets you inspect and modify crash reports before they’re sent to the server, so the Kotlin unhandled exception callback can write the Kotlin stack, and add it after restart, but there’s a lot left to figure out there, and I’m not sure Crashlytics or others allow the same.

It does technically work, though.

However, looking back on the thread, I don’t think you cared so much about remote tools? On the

__crash_info

, I think the piece, or one of the pieces, that I’m missing is what actually gets put in there, and who is intended to read it? I did go through the wireshark and firefox code, but only lightly. I’m definitely not set up for local native dev like that, so I’ve just been reading source. I think writing to it would be easy enough if I understand what’s happening, although I wouldn’t know what to write. Also, I have that background concern of if this is actually a private api, does that mess with app store submissions? That last one is a bit down the road as far as worries go, but still.

Anyway, that’s where I’m at this morning. I rabbit holed a bit on this yesterday, but there’s a whole bunch of things I really should be focused on this week, so I’m probably not going to make much progress for a bit.

Rick Clephas

05/25/2022, 2:42 PM

Also, I have that background concern of if this is actually a private api, does that mess with app store submissions?

As long as Swift is using the same that shouldn’t be an issue, right? Also if Crashlytics is aware of it then it’s already part of your app.

kpgalligan

05/25/2022, 3:23 PM

It doesn’t seem like

__crash_info

is a problem, but I’m not sure that it’s considered private either. Poorly documented for sure, but not sure it’s something Apple cares about. but, again, I’m also not sure it’ll do much for the crash reports, at least for stack traces.

👍 1

Rick Clephas

05/25/2022, 3:52 PM

Bugsnag at least lets you inspect and modify crash reports before they’re sent to the server … and I’m not sure Crashlytics or others allow the same.

Yes if automatic collection is disabled you can update the report before it’s send: https://firebase.google.com/docs/reference/swift/firebasecrashlytics/api/reference/Classes/Crashlytics#checkandupdateunsentreports Though there is no field for a stacktrace, but you could add it as logs or as a custom value or something.

Conrad Kramer

05/25/2022, 4:09 PM

Yeah, a few things: • I care primarily about local crash reports. I run UI integration tests on GitHub actions and my app crashes in one, but the report in the xcresult was useless, which is why I am looking into this in the first place • As for reporting, I am always just going to use Apple’s crash reporting functionality. On macOS I might have a custom reporting functionality, but it will still use the Apple crash reports that are written to disk. Out of process crash reporting is just more robust • The backtrace functionality does work – NSException actually uses it. I remember reading a lot of “Application Specific Backtrace” sections when I was reading reports at Apple. I plan on populating it with the Kotlin exception’s backtrace • Kotlin’s built in exception reporting is very much a hack. I'll likely write a diff for the Kotlin runtime to use crash_info (as that is where it belongs, in the runtime), but compiling Kotlin sounds like a PITA • Haven't gotten it working locally quite yet, but working on it

kpgalligan

05/25/2022, 5:12 PM

when I was reading reports at Apple

Apologies in advance for the endless list of questions I might throw at you in the future

As for reporting, I am always just going to use Apple’s crash reporting functionality

We’re primarily focused on 3rd party tools, but that’s mostly because that’s what our clients are using. Certainly interested to see what you figure out.

The backtrace functionality does work – NSException actually uses it. I remember reading a lot of “Application Specific Backtrace” sections

I’d definitely love to see how this works. The apple-side internals are a bit out of my wheelhouse, and I’m not sure the 3rd party tools wouldn’t report this, but would need to try it and see how it goes.

I’ll likely write a diff for the Kotlin runtime to use crash_info (as that is where it belongs, in the runtime), but compiling Kotlin sounds like a PITA

I wouldn’t say compiling Kotlin is the easiest, but it’s not too bad once you get it set up. We’re hacking around compiler changes now. If you have thoughts on what that should look like we might be able to try some things our, or just assist getting local dev working for you if needed.

Conrad Kramer

05/26/2022, 6:16 PM

I got it working in pure Kotlin. Originally, I had some C code to generate a

__crash___info

section, but the crash info section seemingly only gets checked for system libraries. I updated the code to find an existing section in a system library and write to that

kpgalligan

05/26/2022, 6:19 PM

That’s interesting. This is definitely a bit out of my wheelhouse, but I’m surprised you can write that to a system library. I’d definitely like to try this out if you make anything public and/or just post some code. I’d like to see if the crash reporting libraries we’re using pick up that data.

👍 1

Conrad Kramer

05/26/2022, 6:22 PM

It is the data section of a system library, which is read write (it writes to it just as the system library itself would) but yes! I am landing it in my codebase first: https://github.com/conradev/Wallet/pull/9/files but I will consider making it into a Kotlin library that people can drop in later – have never made or setup a Kotlin library on Github before

👀 1

Firefox and Chrome both have functionality to read the info out, at least the message part

kpgalligan

05/26/2022, 6:29 PM

Yeah, I saw that for both. Crashlytics does that too, but again, just the message. Not sure they don’t also get the rest, but the only code that used the defined structure for that data type (that I could find) was pulling the message string. We also use bugsnag and I haven’t started poking around the client code for that. In any case, I’d love to see if anything interesting makes its way out after stuffing data in.

I was curious about the signature. Wasn’t sure if one needed to worry about that. Guess not 🙂

If you want to do a library, we work on that quite a bit, so can chat/answer questions.

There’s not much different, except sometimes publishing.

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