google-ai-edge_LiteRT/g3doc/instructions/CMAKE_BUILD_INSTRUCTIONS.md

LiteRT CMake Build Instructions

Use this guide to configure and build the LiteRT runtime with CMake on macOS The instructions cover both Android cross-compilation targets (built from Linux and Mac OS) machine and native macOS and Linux builds.

Common Build Steps

Install CMake 4.0.1 from: https://github.com/kitware/cmake/releases

All build presets expect you to work from the repository root:

cd ./litert

The generated build trees live under cmake_build*. Parallel builds can be controlled via -j with the desired core count.

Available Build Flavors

LiteRT supports both Release and Debug build flavors:

Preset	Platform	Build Type	Output Directory
default	Host (macOS/Linux)	Release	cmake_build
default-debug	Host (macOS/Linux)	Debug	cmake_build_debug
android-arm64	Android arm64	Release	cmake_build_android_arm64
android-arm64-debug	Android arm64	Debug	cmake_build_android_arm64_debug

Release builds use -O3 -DNDEBUG for optimized production binaries. Debug builds use -O0 -g for debugging with full symbol information.

Android (arm64) Cross-Compilation

1. Install the Android NDK and export the path so CMake can find it:

   export ANDROID_NDK_HOME=/absolute/path/to/android-ndk-r27
   

2. Configure host-side flatbuffer tools

   cmake --preset android-arm64;
   

3. Configure the LiteRT Android build using the provided preset and point to the generated FlatBuffers tools:

   # For Release build:
   cmake --preset android-arm64 \
     -DTFLITE_HOST_TOOLS_DIR="$(cd ../host_flatc_build/_deps/flatbuffers-build && pwd)"
   
   # For Debug build:
   cmake --preset android-arm64-debug \
     -DTFLITE_HOST_TOOLS_DIR="$(cd ../host_flatc_build/_deps/flatbuffers-build && pwd)"
   

4. Build LiteRT for Android:

   # For Release build:
   cmake --build cmake_build_android_arm64 -j
   
   # For Debug build:
   cmake --build cmake_build_android_arm64_debug -j
   

Artifacts such as static libraries will be emitted under the corresponding build directory (cmake_build_android_arm64 or cmake_build_android_arm64_debug).

Host Build from Mac OS and Linux

1. Configure the default host preset:

   # For Release build:
   cmake --preset default
   
   # For Debug build:
   cmake --preset default-debug
   

2. Build LiteRT:

   # For Release build:
   cmake --build cmake_build -j
   
   # For Debug build:
   cmake --build cmake_build_debug -j
   

Customize your build target

Customizing CMake Builds

Use CMake options to control which toolchains and features are compiled into your targets. E.g.:

cmake -S . -B build-release \
      -DCMAKE_BUILD_TYPE=Release \
      -DLITERT_AUTO_BUILD_TFLITE=ON \
      -DLITERT_ENABLE_GPU=OFF \
      -DLITERT_ENABLE_NPU=OFF \
      -DLITERT_DISABLE_KLEIDIAI=ON \
      -DLITERT_HOST_C_COMPILER=/usr/bin/clang \
      -DLITERT_HOST_CXX_COMPILER=/usr/bin/clang++
cmake --build build-release --target dispatch_api_Qualcomm_so -j8

• LITERT_HOST_C_COMPILER / LITERT_HOST_CXX_COMPILER let you point the helper host tools at any Clang/GCC installation without editing CMakeLists.txt.
• LITERT_DISABLE_KLEIDIAI keeps x86 host builds reproducible by skipping KleidiAI; set it to OFF whenever you want to bundle the delegate.
• Always pass -DCMAKE_BUILD_TYPE=Release (or the equivalent preset) when you need the optimized artifact. This makes CMake use -O3 -DNDEBUG for you.

Producing Minimum-Size Vendor Libraries

At link time enable dead-stripping so dispatch libraries match Bazel’s size:

• macOS: add -DCMAKE_SHARED_LINKER_FLAGS_RELEASE="-Wl,-dead_strip -dead_strip_dylibs" (and the same for CMAKE_EXE_LINKER_FLAGS_RELEASE if you want the executeables stripped). After building, run strip -x path/to/libLiteRtDispatch_Qualcomm.dylib.
• Linux: add -DCMAKE_SHARED_LINKER_FLAGS_RELEASE="-Wl,--gc-sections" and run strip --strip-unneeded path/to/libLiteRtDispatch_Qualcomm.so (or make it a POST_BUILD command).

These flags can live directly in cmake --preset … entries in CMakePresets.json so every developer in your team gets the same configuration.

Troubleshooting Tips

• Delete the corresponding cmake_build* directory if you change toolchains or major configuration options, then rerun the configure step.
• Inspect CMakeCache.txt inside each build tree for resolved dependency paths.