From Source to Sorcery – Kotlin Native's Interop Magic
8 hours ago
- #C Interop
- #Kotlin/Native
- #Desktop Development
- Kotlin/Native compiles Kotlin to native machine code, enabling direct access to C libraries and system APIs on macOS, Windows, and Linux.
- Interop workflow involves translating C headers into Kotlin APIs and compiling Kotlin code with these bindings into a platform binary.
- Definition file (.def) configures the Clang parser and carries link flags, specifying headers, package names, and platform-specific compiler/linker options.
- Gradle configuration for desktop targets involves enabling Kotlin Multiplatform plugin and configuring cinterops for each target.
- Memory management in Kotlin/Native includes safe allocation patterns like `memScoped` for temporary allocations and `nativeHeap` for manual lifetime management.
- Callbacks from C to Kotlin can be achieved using `staticCFunction` for non-capturing callbacks and `StableRef` for passing state through user data.
- Strings and encoding require careful handling, with `toKString` for reading C strings and `string.cstr` or `wcstr` for passing Kotlin strings to C.
- Platform-specific considerations include linking frameworks on macOS, system paths on Linux, and MinGW setup on Windows.
- Error handling patterns involve checking return codes and `errno`, with idiomatic Kotlin wrappers for C functions.
- Performance considerations highlight the overhead of interop boundaries and suggest profiling and potential C shims for critical code.
- Debugging tips include Gradle build flags, runtime logging, and platform debuggers to diagnose issues.
- A checklist for new desktop interop emphasizes tight `headerFilter`, safe allocation patterns, and early testing on each target platform.