Compile Automake (configure) based project using Android NDK - android-ndk

Question

I want to compile a number of libraries for Android using the NDK toolchain. I'm having trouble compiling libiconv, libtiff, libxml2 for example and validate they are built correctly for each target architecture. How can I for example compile a trivial project like libiconv and validate that it was built correctly?

Answer 1

Example by cross-compiling libiconv
You can find these files on GitHub
Build a standalone toolchain
When compiling using Automake you'll need a standalone toolchain that embodies one target architecture and a specific platform revision. The procedure is outlined in the following script.
generate-standalone.sh
#!/bin/bash
ANDROID_NDK_DIR=/opt/android-ndk-r13b
ANDROID_API=19
ANDROID_STL=gnustl
INSTALL_PREFIX=/opt/standalone-r13b
declare -a COMPILE_ARCHITECTURES=("arm" "x86")
pushd ${ANDROID_NDK_DIR}
for ARCH in "${COMPILE_ARCHITECTURES[#]}"
do
INSTALL_DIR=${INSTALL_PREFIX}-${ARCH}
build/tools/make_standalone_toolchain.py \
--arch ${ARCH} \
--api ${ANDROID_API} \
--stl ${ANDROID_STL} \
--install-dir ${INSTALL_DIR}
done
popd
Replace config.sub and config.guess
On some older projects you'll find that the config.guess and config.sub files won't recognize the Android NDK toolchain so you'll need to grab a newer one from automake. In this project I copied the files from Automake 1.15 and just overwrote the ones in the libiconv project.
Compiling for 3 architectures
Flags chosen for the architectures come from Google's ABI Management and Standalone Toolchain pages.
Note: I haven't compiled 64-bit targets in this example. I would need to raise the Android API to 21 to add ARM64 and x86_64.
ANDROID_NDK_DIR=/opt/standalone-r13b
LIBICONV_INSTALL_DIR=${HOME}/Development/libiconv
declare -a COMPILE_ARCHITECTURES=("arm" "armv7a" "x86")
SAVED_PATH="${PATH}"
for ARCH in "${COMPILE_ARCHITECTURES[#]}"
do
COMPILER_GROUP=""
COMPILER_PREFIX=""
case ${ARCH} in
"arm" )
COMPILER_GROUP=arm
;;
"armv7a" )
COMPILER_GROUP=arm
;;
"x86" )
COMPILER_GROUP=x86
;;
esac
export ANDROID_NDK_ROOT="${ANDROID_NDK_DIR}-${COMPILER_GROUP}"
ANDROID_NDK_BIN="${ANDROID_NDK_ROOT}/bin"
ANDROID_SYSROOT_DIR="${ANDROID_NDK_ROOT}/sysroot"
export PATH="${ANDROID_NDK_BIN}:${SAVED_PATH}"
export CFLAGS="--sysroot=${ANDROID_SYSROOT_DIR}"
export LDFLAGS=""
case ${ARCH} in
"arm" )
ABI_NAME=armeabi
COMPILER_PREFIX=arm-linux-androideabi
;;
"armv7a" )
ABI_NAME=armeabi-v7a
COMPILER_PREFIX=arm-linux-androideabi
CFLAGS="${CFLAGS} -march=armv7-a -mfpu=neon -mfloat-abi=softfp -mthumb"
LDFLAGS="${LDFLAGS} -march=armv7-a -Wl,--fix-cortex-a8"
;;
"x86" )
ABI_NAME=x86
COMPILER_PREFIX=i686-linux-android
CFLAGS="${CFLAGS} -march=i686 -mtune=intel -mssse3 -mfpmath=sse -m32"
;;
esac
export CC=${ANDROID_NDK_BIN}/${COMPILER_PREFIX}-gcc
export CPP=${ANDROID_NDK_BIN}/${COMPILER_PREFIX}-cpp
export CXX=${ANDROID_NDK_BIN}/${COMPILER_PREFIX}-g++
export LD=${ANDROID_NDK_BIN}/${COMPILER_PREFIX}-ld
export AR=${ANDROID_NDK_BIN}/${COMPILER_PREFIX}-ar
export RANLIB=${ANDROID_NDK_BIN}/${COMPILER_PREFIX}-ranlib
export STRIP=${ANDROID_NDK_BIN}/${COMPILER_PREFIX}-strip
echo "---- Compiling for ${ARCH}"
./configure --enable-static --host="${COMPILER_PREFIX}" --prefix="${LIBICONV_INSTALL_DIR}/${ABI_NAME}"
make clean
make -j4
make install
done
export PATH="${SAVED_PATH}"
Validating the libraries target the desired architecture
From the NDK you can find arm-linux-androideabi-readelf to determine if for example I'm using Thumb-1 or Thumb-2 instructions in armeabi and armeabi-v7a respectively.
arm-linux-androideabi-readelf -A libiconv.so.2.5.1.so
armeabi
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "5TE"
Tag_CPU_arch: v5TE
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-1
Tag_FP_arch: VFPv2
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align_needed: 8-byte
Tag_ABI_enum_size: int
Tag_ABI_optimization_goals: Aggressive Speed
armeabi-v7a
If your project has support for advanced features like NEON you'll definitely want to validate that you've compiled the library with the correct options.
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "ARM v7"
Tag_CPU_arch: v7
Tag_CPU_arch_profile: Application
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-2
Tag_FP_arch: VFPv3
Tag_Advanced_SIMD_arch: NEONv1
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align_needed: 8-byte
Tag_ABI_enum_size: int
Tag_ABI_HardFP_use: Deprecated
Tag_ABI_optimization_goals: Aggressive Speed
Tag_CPU_unaligned_access: v6