I’m working in Kotlin/Native. I’d like to create a...

# kotlin-native

[jessewilson]

I’m working in Kotlin/Native. I’d like to create a thread with a non-default stack size because the Mac’s default stack size of 512 KiB isn’t sufficient.

As-is, the Crash Reports tab of Console.app is reporting a SIGBUS error on a STACK GUARD field. I believe it’s telling me that my program used more stack than was allocated.

Crashed Thread:        5

Exception Type:        EXC_BAD_ACCESS (SIGBUS)
Exception Codes:       KERN_PROTECTION_FAILURE at 0x000000016b0e1120
Exception Codes:       0x0000000000000002, 0x000000016b0e1120

Termination Reason:    Namespace SIGNAL, Code 10 Bus error: 10
Terminating Process:   exc handler [67893]

VM Region Info: 0x16b0e1120 is in 0x16b0e0000-0x16b0e4000;  bytes after start: 4384  bytes before end: 11999
      REGION TYPE                    START - END         [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL
      Stack                       16b058000-16b0e0000    [  544K] rw-/rwx SM=PRV  thread 4
--->  STACK GUARD                 16b0e0000-16b0e4000    [   16K] ---/rwx SM=NUL  ... for thread 5
      Stack                       16b0e4000-16b16c000    [  544K] rw-/rwx SM=PRV  thread 5

(I triggered a similar error by writing a recursive function.)

Unfortunately I can’t find build-in APIs to manipulate the stack size of spawned threads. Worker.start() accepts a thread name, but nothing like pthread_attr_setstacksize. I also couldn’t find a straightforward way to create a thread without going through the Worker API.

Any recommendations? Should I open a ticket to request a new API on Worker?

[kevin.cianfarini]

Jesse, I know this doesn’t help the stack size issue, but Worker is the defacto way to use platform threads in K/N. I was trying to find a different API as well when trying to figure out how to register signal handlers on workers in K/N.

I don’t envy the position you’re in!

[russhwolf]

FYI the worker APIs will eventually be going away, per a new opt-in warning in Kotlin 1.9
https://youtrack.jetbrains.com/issue/KT-54702/Native-mark-Worker-and-related-APIs-as-obsolete
https://github.com/jetbrains/kotlin/commit/af9252aa9625f270f35898fc95260c5b4d114436#diff-ebf739ffccf1ef1ea546c2ac760e9215c39d446de929aa5cb8fbd6f58fa40a3c

[jessewilson]

Yeah, though there’s no replacement yet as far as I can see

[Alexander Shabalin [JB]]

Hi! You can create threads via interop libs, if that suits you. For example, if targeting Apple platforms using NSThread is an option:

import platform.Foundation.*
…
    val thread = NSThread {
        println("Hello from the other thread")
        …
    }
    thread.stackSize = …
    thread.start()
…

It's also possible to use pthreads but it'll be much less convenient:

import kotlinx.cinterop.*
import platform.posix.*
…
    memScoped {
        val thread = alloc<pthread_tVar>()
        val attr = alloc<pthread_attr_t>()
        pthread_attr_init(attr.ptr)
        pthread_attr_setstacksize(attr.ptr, …)
        pthread_create(thread.ptr, attr.ptr, staticCFunction<COpaquePointer?, COpaquePointer?> {
            println("Hello from the other thread")
            …
            null
        }, null)
        pthread_attr_destroy(attr.ptr)
    }
…

(in the code above error handling is omitted completely)