Android JNI & NDK

Everything that leaves the pure Kotlin/Java world: native shared libraries (.so), the JNI boundary, cross-boundary refs and exceptions, and the modern Android packaging constraints (16 KB pages, split APKs, App Bundles).

Pair with kotlin-performance for measuring native-call overhead, smali-dex-patching for offensive patching of the managed side, and mobile-technique for auditing shipped native code.

When to activate

• Embedding a C/C++/Rust library in a Kotlin/Java app
• Debugging JNI reference leaks, LocalReferenceTable overflow, or ArrayIndexOutOfBoundsException originating in native code
• Diagnosing a native crash (SIGSEGV, SIGABRT) from a tombstone or Play Console ANR
• Migrating to 16 KB page-size compliance for Google Play (deadline Nov 2025 for apps targeting API 35+)
• Building AAB / APK with multiple ABIs and understanding split delivery
• Reverse-engineering a shipped .so to understand what native code an app runs

Core mental model