C Development Reference

Skip supports calling C and C++ code from your cross-platform Swift, with different mechanisms depending on which mode you are using.

Skip Fuse (Native Mode)

In Fuse mode, your Swift compiles natively for Android, so Swift’s built-in C and C++ interoperability works exactly as it does on iOS. You can use Swift’s import of C modules, call C functions directly, and work with C pointers and structs without any bridging layer.

This means you can use C libraries (like SQLite, libxml2, or your own native code) on both platforms with no additional effort beyond what you would do on iOS. The Swift Android SDK ↗ includes the Android NDK, so common system libraries are available.

For examples of C interop in a Fuse project, see the skipapp-travelposters-native ↗ sample.

Skip Lite (Transpiled Mode)

In Lite mode, your Swift is transpiled to Kotlin, so Swift’s native C interop is not available. Instead, Skip provides the skip-ffi module, which uses JNA (Java Native Access) ↗ to call C functions from the transpiled Kotlin code.

With skip-ffi, you write your C function declarations in Swift, and Skip transpiles them into JNA calls on Android. This lets you share C library code across both platforms from a single Swift codebase.

For a detailed walkthrough, see the blog post Sharing C code between Swift and Kotlin for iPhone and Android apps.

Which approach to choose

If your project relies heavily on C or C++ libraries, Fuse mode is the simpler path because Swift’s native interop works identically on both platforms. If you are using Lite mode for other reasons (such as maximizing Kotlin interoperability), skip-ffi provides a solid bridge to C libraries through JNA.