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Native interoperability (cinterop)

Kotlin/Native provides the cinterop tool to facilitate interaction with C and Objective-C libraries. The Kotlin Toolchain supports cinterop out of the box with zero configuration for the common use case.

Basic usage

To add a C or Objective-C interop to your multiplatform module:

  1. Create a cinterop directory in your module root (alongside src and test).
  2. Drop your .def files into this directory.

The Kotlin Toolchain will automatically detect these files and configure the cinterop tool for all applicable native platforms. No additional configuration in your module.yaml is required.

Platform-specific definitions

You can use the @<platform> qualifier for the cinterop directory to limit interop definitions to specific platforms or platform families.

At the file level vs. directory level

The .def file format already supports platform-specific configuration for the library, for example: compilerOpts.linux vs. compilerOpts.osx.

So it is possible to use a single .def file in the common cinterop directory instead of having separate platform-specific files under, e.g., cinterop@linux and cinterop@macos. Both approaches are currently valid - use the one you prefer.

Bundled C headers (include directory)

If your interop needs C header files that are not available on the system (for example, headers vendored alongside your module), you can place them in an include directory next to your .def files.

The Kotlin Toolchain will automatically detect this directory and pass it to the cinterop tool as an additional header search path (equivalent to passing -I<path-to-include> as a compiler option). No configuration in your module.yaml is required.

Advanced usage

If you need the .def file generated or provisioned (for example, to implement custom library location or provisioning logic), you can write a plugin for this. See the relevant docs for more details on how to contribute cinteropDefinitions.