KLIB Commonizer

You can use platform-dependent libraries, such as Foundation, UIKit, posix, in source sets shared among several native targets. For each project that has native source sets that depend on a shared native source set, the special tool KLIB Commonizer automatically produces:

• One library in the KLIB format (*.klib) with the common API of the library that includes declarations that are identical among all platforms and expect declarations for the APIs that differ from platform to platform.
• One KLIB for each platform-specific source set that contains the actual declarations and the declarations that are available only on this particular platform.

                    commonMain
                        |
                        |
                     iosMain ----------▶ Foundation (common)
                      /   \              ┌──────────────────┐
                     /     \             │ expect class ... │
         iosArm64Main      iosX64Main    │ expect fun ...   │
                |             |          └──────────────────┘
                |             |
                ▼             ▼
Foundation (ios_arm64)     Foundation (ios_x64)
┌────────────────────┐     ┌──────────────────┐
│ actual class ...   │     │ actual class ... │
│ actual fun ...     │     │ actual fun ...   │
└────────────────────┘     └──────────────────┘

The resulting KLIBs are automatically added to the dependencies of the corresponding shared native and platform-specific source sets.

There are few limitations in the current version of KLIB Commonizer:

• It supports only interop libraries shipped with Kotlin/Native. It doesn't support KLIBs that are produced from C-interop or Kotlin code.

• It works only for a native source set that is shared among platform-specific source sets and these source sets themselves. It doesn‘t work for native source sets shared at higher levels of the source set hierarchy. For example, if you have nativeDarwinMain that includes iosMain with iosArm64Main and iosX64Main, and watchosDeviceMain with watchosArm64Main and watchosArm32Main, the KLIB Commonizer will work separately for iosMain and watchosDeviceMain and won’t work for nativeDarwinMain.

                    commonMain
                        |
                        |
                 nativeDarwinMain    <--- Commonizer is NOT applied
                    /       \
                   /         \
            iosMain         watchosDeviceMain  <--- Commonizer is applied
             /   \                /  \
            /     \              ..  ..
  iosArm64Main   iosX64Main 
  

• It does not process targets that are not available at the current host machine. For example, if you have a project with nativeMain source set that includes macosX64Main, linuxX64Main and mingwX64Main, and you run the KLIB Commonizer for this project on MacOS machine, then mingwX64Main source set will not be processed as far as mingw_x64 target is absent in Kotlin/Native distribution for MacOS. The KLIB Commonizer will print the appropriate warning message and will work only for macosX64Main and linuxX64Main source sets. You can find the list of targets supported on various hosts here: https://kotlinlang.org/docs/reference/mpp-supported-platforms.html

  Kotlin KLIB commonizer: Please wait while preparing libraries.
  [Step 1 of 1] Preparing commonized Kotlin/Native libraries for targets [macos_x64, linux_x64, mingw_x64] (137 items)
    Warning: No platform libraries found for target [mingw_x64]. This target will be excluded from commonization.
    ...
  

  In the degenerate case when all but one targets are not available at the host machine, the KLIB Commonizer is not launched.