Android cross compilation
=========================

Android port was originally written by Ladislav Vaiz (OK1ZIA, 2012)
using a standalone Android.mk build system with a custom ltdl/dl
wrapper (since removed).  The present autotools-based cross-compile
instructions supersede that approach.

Hamlib can be cross-compiled for Android using the NDK's standalone
toolchains.  API level 28 is the minimum supported version; the
following example targets 64-bit ARM (aarch64) with API 28.


Prerequisites
-------------

Install the Android NDK (e.g. via Android Studio's SDK Manager or
`sdkmanager`).  The examples below use NDK r28 at the default install
location under `~/Android/Sdk/ndk/`.

The host toolchain used is `linux-x86_64`; adjust for other host
platforms (e.g. `darwin-x86_64` or `windows-x86_64`).

USB support (libusb) is not currently available in the Android cross
build, so `--without-libusb` is required.


Build script example
--------------------

The following environment variables set up the NDK toolchain for a
64-bit ARM target:

    export NDK=$HOME/Android/Sdk/ndk/28.0.12433566
    export TOOLCHAIN=$NDK/toolchains/llvm/prebuilt/linux-x86_64
    export TARGET=aarch64-linux-android
    export API=28

    export AR=$TOOLCHAIN/bin/llvm-ar
    export AS=$TOOLCHAIN/bin/llvm-as
    export CC=$TOOLCHAIN/bin/${TARGET}${API}-clang
    export CXX=$TOOLCHAIN/bin/${TARGET}${API}-clang++
    export LD=$TOOLCHAIN/bin/ld
    export RANLIB=$TOOLCHAIN/bin/llvm-ranlib
    export STRIP=$TOOLCHAIN/bin/llvm-strip

    ./bootstrap
    ./configure --host=$TARGET --without-libusb
    make

To build for 32-bit ARM, use `TARGET=armv7a-linux-androideabi` instead
(also with `API=28`).

To build for x86-64 Android emulators, use `TARGET=x86_64-linux-android`.


Notes
-----

- `./bootstrap` is only needed when building from a Git checkout, not
  from a release tarball.
- The resulting binaries run on Android but must be deployed with the
  NDK's libc++_shared.so or linked statically.
- Only the Hamlib C/C++ library is built; language bindings (Python, Perl,
  etc.) have not been tested in this configuration.