A work-in-progress repository of the scripts, discoveries, tips and traps we're discovering during the process of cross-compiling GNUnet for Android.
This repo contains a set of scripts in https://github.com/commercetest/cross-compiling-gnunet/tree/main/scripts which we are iteratively refining.
Key elements:
- root folder for the cross-compilation; set to
~/x-compile-gnunet-sandboxfor now - root folder for the target architecture's binaries that Android's build system uses that is mapped using
CMakeLists.txt - inter-dependencies folder, which contains various folders for intermediate build outputs used by other dependencies.
| Libraries | Source of Library | Version | How built | Local location on build machine | Evidence |
|---|---|---|---|---|---|
| liblibsodium | Text | Text | Text | Text | Text |
| libgpg-error | fork of github-mirror | 1.49 | Text | ~/x-compile-gnunet-sandbox/libgpg-error-with-android | file ./src/.libs/libgpg-error.so |
| libgcrypt | https://github.com/gpg/libgcrypt.git | 1.10.3 | Text | Text | Text |
| ltdl | https://git.savannah.gnu.org/git/libtool.git | HEAD (v2.5.0) | Text | ~/x-compile-gnunet-sandbox/libtool-for-android | file libltdl/.libs/libltdl.so |
| unistring | https://git.savannah.gnu.org/git/libunistring.git | HEAD (v1.2) | Text | ~/x-compile-gnunet-sandbox/libunistring-for-android | file ./lib/.libs/libunistring.so |
| gmp | https://gmplib.org/devel/repo-usage | 6.2 | Text | ~/x-compile-gnunet-sandbox/gmp-6_2_for_android | file ./.libs/libgmp.so |
| zlib | Text | Text | Text | Text | Text |
(The table is an extended edition of https://hedgedoc.c3d2.de/4_Gov7XPT9yE3JHfiTH8nQ?view)
The evidence column provides a summary of how to check whether the results are OK. Generally the output of the file command will include the intended architecture of the library|libraries that were generated.
libgpg-error generates various files used by libgcrypt. A set of shared folders are created in the root of the cross-compilation root ~/x-compile-gnunet-sandbox/
mkdir ~/x-compile-gnunet-sandbox/cross-build/
mkdir ~/x-compile-gnunet-sandbox/cross-build/bin
mkdir ~/x-compile-gnunet-sandbox/cross-build/include
mkdir ~/x-compile-gnunet-sandbox/cross-build/lib
# TARGETDIR is set here and incorporated into the build outputs (particularly src/gpg-error-config)
export TARGETDIR=~/x-compile-gnunet-sandbox/cross-build/
echo $TARGETDIR
# standard build steps
./autogen.sh
build="$(build-aux/config.guess)"
./configure --enable-maintainer-mode -prefix=$TARGETDIR --host=$TARGET --build=$build --disable-doc
The following steps only need to be performed once per architecture. You will need a suitable physical Android device, or emulator, for each target Android architecture.
cd src
make gen-posix-lock-obj
# discover which Android devices (emulators and/or physical devices) are available to use
adb devices
# from the list of devices, pick the serial number and use it in the rest of the steps that use adb
# Obtain the Android architecture
adb -s FRTBB80301420573 shell getprop ro.product.cpu.abi
# Transfer the script that will generate the architecture specific header file
adb -s FRTBB80301420573 push gen-posix-lock-obj /data/local/tmp
# adb shell is similar to an SSH session
adb -s FRTBB80301420573 shell
# After closing the adb shell, retrieve the generated header file
adb -s FRTBB80301420573 pull /data/local/tmp/tmp.h .
# This is a debugging step
awk 'NR==1 {print $2}' tmp.h
# followed by renaming and relocating the file using the contents of the first line
mv tmp.h "syscfg/$(awk 'NR==1 {print $2}' tmp.h)"
# As the generated file on Android includes some extraneous information
# the file name isn't as expected; so we make a copy to a suitable name
cd syscfg/
ls -lart # check the most recent file is the renamed tmp.h
# Remove the architecture-specific element from the name of the header file
cp lock-obj-pub.armv7a-unknown-linux-androideabi.h lock-obj-pub.linux-android.h
Each make continues from here (the Android stuff only needs doing once per Android architecture). Beware of accidentially using the wrong architecture specific header file (generated in the previous steps).
# Continue the standard make process
cd ../..
make
# Check the generated shared library is for the expected Android architecture
file ./src/.libs/libgpg-error.so
Copy various build outputs to the cross-build folders:
cp src/gpg-error-config ~/x-compile-gnunet-sandbox/cross-build/bin/
cp src/gpgrt-config ~/x-compile-gnunet-sandbox/cross-build/bin/
cp src/.libs/libgpg-error.so ~/x-compile-gnunet-sandbox/cross-build/lib/
cp src/gpg-error.h ~/x-compile-gnunet-sandbox/cross-build/include/
hg outgoing # check for any uncommitted changes to the cloned repo
./.bootstrap
./configure --host=$TARGET --enable-maintainer-mode
file gmp.h| grep 'C source'
echo $? # should be 0
file ./.libs/libgmp.so | grep 'ARM aarch64'
echo $? # should be 0
We're currently building release 1.10.3 and make some changes to the configuration; TBD how long-lived these will be.
git checkout libgcrypt-1.10.3
The following are subject to change as I learn and understand more about autogen.sh and configure. They work on my machine for one Android build target so far...
/autogen.sh
./configure --host=$TARGET --with-libgpg-error-prefix=/home/julian/x-compile-gnunet-sandbox/cross-build/ --prefix=/home/julian/x-compile-gnunet-sandbox/cross-build/ --exec-prefix=/home/julian/x-compile-gnunet-sandbox/cross-build/ --disable-doc
make
echo $? # the return value should be 0
file src/.libs/libgcrypt.so
Compiled from HEAD in the master branch, last tagged as v2.5.0
git clone https://git.savannah.gnu.org/git/libtool.git libtool-for-android
cd libtool-for-android/
Build steps
./bootstrap
./configure --host=$TARGET
make
echo $? # the return value should be 0
file libltdl/.libs/libltdl.so | grep 'ARM aarch64'
echo $? # should be 0
file libltdl/ltdl.h | grep 'C source'
echo $? # should be 0
The library information should reflect the target architecture (ARM or x86, 32-bit or 64-bit).
Files to copy to the Android project (this example is for ARMv8 (i.e. 64-bit)
cp ./libltdl/.libs/libltdl.so ~/AndroidStudioProjects/GNUnet/distribution/libtool/lib/arm64-v8a/
cp libltdl/ltdl.h ~/AndroidStudioProjects/GNUnet/distribution/libtool/lib/arm64-v8a/include/
Note: the mirror on github.com was last updated in 2021. GNU hosts the current repo https://git.savannah.gnu.org/git/libunistring.git
git clone ...
# Configure environment variables
./gitsub.sh pull
Build steps
./autogen.sh
./configure --host=$TARGET
make
file ./lib/.libs/libunistring.so | grep 'ARM aarch64'
echo $? # should be 0
file libltdl/ltdl.h | grep 'C source'
echo $? # should be 0
YMMV depending on what your development environment and OS release already provide. To help improve reproducibility here are packages that needed installing to make these dependencies.
hg(mercurial) andyaccneeded to make gmp. In Ubuntu 22.04 LTS these were provided usingsudo apt install mercurial bison.gperfinstalled usingsudo apt install gperfhelp2maninstalled usingsudo apt install help2manfig2devfor libcrypt usingsudo apt install fig2dev
- Environment variables are set using the examples in the Autoconf section of https://developer.android.com/ndk/guides/other_build_systems
- https://github.com/commercetest/libgpg-error-with-android/tree/updates-to-build-for-android documents specific steps for building on/for Android devices
- https://www.repeato.app/determining-the-arm-processor-version-on-your-android-device/ and https://android.stackexchange.com/questions/188725/determine-device-architecture-arm-arm64-x86-with-adb-getprop on obtaining the ABI (Android architecture) supported by an Android device.
The code is currently available under the MIT license and text available under the CC BY 4.0 license. For the avoidance of doubt any portion of this material may be incorporated into projects licensed with an approved GNU GPL license (see https://www.gnu.org/licenses/gpl-howto.html).