Building Android binary¶

In this article, we briefly describe how to build Android binary using Android NDK cross-compiler on Debian Linux.

The easiest way to build android binary is use Dockerfile.android. See Dockerfile.android for more details. If you cannot use Dockerfile.android for whatever reason, continue to read the rest of this article.

We offer android-config and android-make scripts to make the build easier. To make these script work, NDK toolchain must be installed in the following way. First, let us introduce ANDROID_HOME environment variable. We need to install toolchain under $ANDROID_HOME/toolchain. An user can freely choose the path for ANDROID_HOME. For example, to install toolchain under $ANDROID_HOME/toolchain, do this in the the directory where NDK is unpacked:

$ build/tools/make-standalone-toolchain.sh \
  --install-dir=$ANDROID_HOME/toolchain \
  --toolchain=arm-linux-androideabi-4.9 \
  --llvm-version=3.5 \
  --platform=android-16

The additional flag --system=linux-x86_64 may be required if you are using x86_64 system.

The platform level is not important here because we don't use Android specific C/C++ API.

The dependent libraries, such as OpenSSL and libev should be built with the toolchain and installed under $ANDROID_HOME/usr/local. We recommend to build these libraries as static library to make the deployment easier. libxml2 support is currently disabled.

We use zlib which comes with Android NDK, so we don't have to build it by ourselves.

If SPDY support is required for nghttpx and h2load, build and install spdylay as well.

Before running android-config and android-make, ANDROID_HOME environment variable must be set to point to the correct path. Also add $ANDROID_HOME/toolchain/bin to PATH:

$ export PATH=$PATH:$ANDROID_HOME/toolchain/bin

To configure OpenSSL, use the following script:

#!/bin/sh

if [ -z "$ANDROID_HOME" ]; then
    echo 'No $ANDROID_HOME specified.'
    exit 1
fi
PREFIX=$ANDROID_HOME/usr/local
TOOLCHAIN=$ANDROID_HOME/toolchain
PATH=$TOOLCHAIN/bin:$PATH

export CROSS_COMPILE=$TOOLCHAIN/bin/arm-linux-androideabi-
./Configure --prefix=$PREFIX android

And run make install to build and install.

We cannot compile libev without modification. Apply this patch before configuring libev. This patch is for libev-4.19. After applying the patch, to configure libev, use the following script:

#!/bin/sh

if [ -z "$ANDROID_HOME" ]; then
    echo 'No $ANDROID_HOME specified.'
    exit 1
fi
PREFIX=$ANDROID_HOME/usr/local
TOOLCHAIN=$ANDROID_HOME/toolchain
PATH=$TOOLCHAIN/bin:$PATH

./configure \
    --host=arm-linux-androideabi \
    --build=`dpkg-architecture -qDEB_BUILD_GNU_TYPE` \
    --prefix=$PREFIX \
    --disable-shared \
    --enable-static \
    CPPFLAGS=-I$PREFIX/include \
    LDFLAGS=-L$PREFIX/lib

And run make install to build and install.

To configure spdylay, use the following script:

if [ -z "$ANDROID_HOME" ]; then
    echo 'No $ANDROID_HOME specified.'
    exit 1
fi
PREFIX=$ANDROID_HOME/usr/local
TOOLCHAIN=$ANDROID_HOME/toolchain
PATH=$TOOLCHAIN/bin:$PATH

./configure \
    --disable-shared \
    --host=arm-linux-androideabi \
    --build=`dpkg-architecture -qDEB_BUILD_GNU_TYPE` \
    --prefix=$PREFIX \
    --without-libxml2 \
    --disable-src \
    --disable-examples \
    CPPFLAGS="-I$PREFIX/include" \
    PKG_CONFIG_LIBDIR="$PREFIX/lib/pkgconfig" \
    LDFLAGS="-L$PREFIX/lib"

And run make install to build and install. After spdylay installation, edit $ANDROID_HOME/usr/local/lib/pkgconfig/libspdylay.pc and remove the following line:

Requires.private: zlib

After prerequisite libraries are prepared, run android-config and then android-make to compile nghttp2 source files.

If all went well, application binaries, such as nghttpx, are created under src directory. Strip debugging information from the binary using the following command:

$ arm-linux-androideabi-strip src/nghttpx