How do you compile a C++ console program to run as an android process?

Question

I wrote a chess engine in C++ which I want to compile to run on the app "Chess for Android".

Here is an excerpt from a post from the author of the app who very very crudely describes how to run a 3rd party chess engine on his app:

Finally, developers can do all development in C/C++ and generate stand-alone native code using the appropriate compiler toolchain (e.g. CodeSourcery for ARM or the toolchain that ships with the NDK). This third approach is used by Chess for Android to import engines that do not ship with the application.

A chess engine is a straightforward program. The application runs, the user sends it commands, the program thinks, and will spit back a string with the details of the best move.

I do NOT need an app with graphics or anything else. it's ONLY a process which is communicated with via stdin/stdout (via pipes really). The "Chess for Android" app takes care of talking to the process, I just need to figure out how in the world to get my engine as a process that can be run by the "Chess for Android" app.

Answer 1

You can build traditional console program for Android in two ways.

1. Using of ndk-build system.

You need to create two extra files: Application.mk:

APP_ABI := armeabi-v7a
APP_PLATFORM := android-16
APP_STL := stlport_static
NDK_TOOLCHAIN_VERSION := 4.8

Android.mk:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := <executable_name>
LOCAL_LDLIBS := -llog -lm # whatever libs you need
LOCAL_CFLAGS := -O3 -UNDEBUG # so on
LOCAL_C_INCLUDES := <list of a non-standard header directories>
LOCAL_SRC_FILES := <sources>
include $(BUILD_EXECUTABLE) # build executable instead of library

The former describes target ABIs, target android level, STL implementation and selects build toolchain. The latter is itself a simpe makefile, and it shouldn't be confusing. See here for detais Then you can start build with next command:

$ ndk-build NDK_PROJECT_PATH=path/to/intermediate/results/dir NDK_LIBS_OUT=path/to/output/dir APP_BUILD_SCRIPT=path/to/Android.mk NDK_APPLICATION_MK=path/to/Application.mk

Also, note that ndk-build adds some flags by default. To check it - add V=1 to above command line.

2. Using of standalone toolchain.

This approach may be useful if you already have build system for your project and you need only cross-compiler. To prepare standalone toochain run e.g next:

$NDK/build/tools/make-standalone-toolchain.sh --arch=arm --platform=android-21 --install-dir=/tmp/my-android-toolchain

And now export path to tools:

$ export PATH=/tmp/my-android-toolchain/bin:$PATH
$ export CC=arm-linux-androideabi-gcc
$ export CXX=arm-linux-androideabi-g++

More info here.