Kotlin/Native FAQ

How do I run my program?

Define a top-level function fun main(args: Array<String>) or just fun main() if you are not interested in passed arguments, please ensure it's not in a package. Also, compiler switch -entry could be used to make any function taking Array<String> or no arguments and return Unit as an entry point.

What is Kotlin/Native memory management model?

Kotlin/Native uses an automated memory management scheme that is similar to what Java or Swift provide.

Learn about the Kotlin/Native memory manager

How do I create a shared library?

Use the -produce dynamic compiler switch, or binaries.sharedLib() in Gradle.

kotlin {
    iosArm64("mylib") {
        binaries.sharedLib()
    }
}

It will produce a platform-specific shared object (.so on Linux, .dylib on macOS, and .dll on Windows targets) and a C language header, allowing the use of all public APIs available in your Kotlin/Native program from C/C++ code.

How do I create a static library or an object file?

Use the -produce static compiler switch, or binaries.staticLib() in Gradle.

kotlin {
    iosArm64("mylib") {
        binaries.staticLib()
    }
}

It will produce a platform-specific static object (.a library format) and a C language header, allowing you to use all the public APIs available in your Kotlin/Native program from C/C++ code.

How do I run Kotlin/Native behind a corporate proxy?

As Kotlin/Native needs to download a platform specific toolchain, you need to specify -Dhttp.proxyHost=xxx -Dhttp.proxyPort=xxx as the compiler's or gradlew arguments, or set it via the JAVA_OPTS environment variable.

How do I specify a custom Objective-C prefix/name for my Kotlin framework?

Use the -module-name compiler option or matching Gradle DSL statement.

【Kotlin】

kotlin {
    iosArm64("myapp") {
        binaries.framework {
            freeCompilerArgs += listOf("-module-name", "TheName")
        }
    }
}

【Groovy】

kotlin {
    iosArm64("myapp") {
        binaries.framework {
            freeCompilerArgs += ["-module-name", "TheName"]
        }
    }
}

How do I rename the iOS framework?

The default name is for an iOS framework is <project name>.framework. To set a custom name, use the baseName option. This will also set the module name.

kotlin {
    iosArm64("myapp") {
       binaries {
          framework {
              baseName = "TheName"
          }
       }
    }
}

How do I enable bitcode for my Kotlin framework?

By default gradle plugin adds it on iOS target.

• For debug build it embeds placeholder LLVM IR data as a marker.
• For release build it embeds bitcode as data.

Or commandline arguments: -Xembed-bitcode (for release) and -Xembed-bitcode-marker (debug)

Setting this in a Gradle DSL:

kotlin {
    iosArm64("myapp") {
        binaries {
            framework {
                // Use "marker" to embed the bitcode marker (for debug builds).
                // Use "disable" to disable embedding.
                embedBitcode("bitcode") // for release binaries.
            }
        }
    }
}

These options have nearly the same effect as clang's -fembed-bitcode/-fembed-bitcode-marker and swiftc's -embed-bitcode/-embed-bitcode-marker.

Why do I see InvalidMutabilityException?

This issue is relevant for the legacy memory manager only. Check out Kotlin/Native memory management to learn about the new memory manager, which has been enabled by default since Kotlin 1.7.20.

It likely happens, because you are trying to mutate a frozen object. An object can transfer to the frozen state either explicitly, as objects reachable from objects on which the kotlin.native.concurrent.freeze is called, or implicitly (i.e. reachable from enum or global singleton object - see the next question).

How do I make a singleton object mutable?

This issue is relevant for the legacy memory manager only. Check out Kotlin/Native memory management to learn about the new memory manager, which has been enabled by default since Kotlin 1.7.20.

Currently, singleton objects are immutable (i.e. frozen after creation), and it's generally considered good practise to have the global state immutable. If for some reason you need a mutable state inside such an object, use the @konan.ThreadLocal annotation on the object. Also, the kotlin.native.concurrent.AtomicReference class could be used to store different pointers to frozen objects in a frozen object and automatically update them.

How can I compile my project with unreleased versions of Kotlin/Native?

First, please consider trying preview versions.

In case you need an even more recent development version, you can build Kotlin/Native from source code: clone Kotlin repository and follow these steps.