opam-android-repository

This OPAM repository contains an OCaml cross-compiler for Google Android, as well as a few OCaml libraries and programs compiled for Android.

Installation notes

Use the following command to add this repository to the list of repositories used by OPAM:

opam repo add android https://github.com/vouillon/opam-android-repository.git

The following command will list the available packages:

opam list | grep android

The Android NDK (Native Development Kit) is automatically downloaded.

On a 64bit Debian or Ubuntu installation, you need to install package gcc-multilib and lib32z1, as we have to build 32 bit OCaml binaries when targeting 32 bit architectures.

Directory structure

Cross-compilation tools use the arm-linux-androideabi- prefix (for instance, arm-linux-androideabi-ocamlc) to differentiate them from standard OCaml tools. For convenience, unprefixed binaries are also available in directory %{bin}%/arm-linux-androideabi/, where %{bin}% is the directory where OPAM normally puts binaries (typically, ~/.opam/4.00.1/bin/ for OCaml 4.00.1).

Ocamlfind can be invoked as either:

• ocamlfind -toolchain android,
• arm-linux-androideabi-ocamlfind,
• %{bin}%/arm-linux-androideabi/ocamlfind.

The Android NDK is in %{lib}%/android-ndk where %{prefix}% is the directory under which OPAM normally puts libraries (typically, ~/.opam/4.00.1/lib/ for OCaml 4.00.1). The C compiler is called with the right options when invoked through the OCaml compilers, so this location only matters if you need to invoke the compiler directly. See the build script for package android-c-openssh for an example of how to do it.

Android libraries and binaries are placed in directory %{prefix}%/arm-linux-androideabi, where %{prefix}% is the directory under which OPAM normally puts libraries and libraries (typically, ~/.opam/4.00.1/ for OCaml 4.00.1). For instance, the path of the unison binary is:

%{prefix}/arm-linux-androideabi/bin/unison

Bytecode programs

There are a few pitfalls regarding bytecode programs. First, if you link them without the -custom directive, you will need to use ocamlrun explicitly to run them. Second, the ocamlmklib command produces shared libraries dll*.so which are not usable. Thus, you need to use the -custom directive to successfully link bytecode programs that uses libraries with mixed C / OCaml code. Shared libraries should eventually be disabled, but at the moment, the ocamlbuild plugin of oasis requires them to be created.

Acknowledgements

Many thanks to Keigo Imai for his OCaml 3.12 cross-compiler patches.