Android NDK
The Android NDK contains prebuilt versions of the native compiler and toolchain. Both the GCC and Clang compilers have traditionally been supported, but active support for GCC ended with NDK revision 14. The device architecture and host OS determine the appropriate version. The prebuilt toolchains are in the toolchains directory of the NDK, which contains one subdirectory for each architecture.
| Architecture | Toolchain name |
|---|---|
| ARM-based | arm-linux-androideabi-<gcc-version> |
| x86-based | x86-<gcc-version> |
| MIPS-based | mipsel-linux-android-<gcc-version> |
| ARM64-based | aarch64-linux-android-<gcc-version> |
| X86-64-based | x86_64-<gcc-version> |
| MIPS64-based | mips64el-linux-android-<gcc-version> |
Besides picking the right architecture, you need to specify the correct sysroot for the native API level you want to target. The sysroot is a directory that contains the system headers and libraries for your target. Native APIs vary by Android API level. Available sysroot directories for each Android API level can be found in $NDK/platforms/. Each API level directory contains subdirectories for the various CPUs and architectures.
One possibility for setting up the build system is exporting the compiler path and necessary flags as environment variables. To make things easier, however, the NDK allows you to create a so-called standalone toolchain, which is a temporary toolchain that incorporates the required settings.
To set up a standalone toolchain, download the latest stable version of the NDK. Extract the ZIP file, change into the NDK root directory, and run the following command:
./build/tools/make_standalone_toolchain.py --arch arm --api 24 --install-dir /tmp/android-7-toolchain
This creates a standalone toolchain for Android 7.0 (API level 24) in the directory /tmp/android-7-toolchain. For convenience, you can export an environment variable that points to your toolchain directory, (we'll be using this in the examples). Run the following command or add it to your .bash_profile or other startup script:
export TOOLCHAIN=/tmp/android-7-toolchain