Android build fails (libfastcdr not found)

I can't build for android following the README instructions. I have the following script:

#!/bin/bash

set -e

AMENT_WS_INSTALL=$HOME/code/ament_java/install_isolated
ANDROID_NDK_ROOT=$HOME/Android/Ndk/android-ndk-r17
ROS2_INSTALL=$HOME/ros2_android/install_isolated

source $AMENT_WS_INSTALL/local_setup.bash

ament build --isolated --cmake-args \
  -DPYTHON_EXECUTABLE=/usr/bin/python3 \
  -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK_ROOT/build/cmake/android.toolchain.cmake \
  -DANDROID_FUNCTION_LEVEL_LINKING=OFF \
  -DANDROID_NATIVE_API_LEVEL=android-21 \
  -DANDROID_TOOLCHAIN_NAME=arm-linux-androideabi-clang \
  -DANDROID_STL=gnustl_shared \
  -DANDROID_ABI=armeabi-v7a \
  -DANDROID_NDK=$ANDROID_NDK_ROOT \
  -DTHIRDPARTY=ON \
  -DCOMPILE_EXAMPLES=OFF \
  -DCMAKE_FIND_ROOT_PATH="$AMENT_WS_INSTALL;$ROS2_INSTALL" \
  -- \
  --parallel \
  --ament-gradle-args \
  -Pament.android_stl=gnustl_shared -Pament.android_abi=armeabi-v7a -Pament.android_ndk=$ANDROID_NDK_ROOT --

The first time running this script it finishes fairly quickly with:

...
-- Installing: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/share/poco_vendor/cmake/poco_vendorConfig.cmake
-- Installing: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/share/poco_vendor/cmake/poco_vendorConfig-version.cmake
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/share/poco_vendor/environment/ament_prefix_path.sh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/share/poco_vendor/environment/path.sh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/share/poco_vendor/environment/library_path.sh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/share/poco_vendor/local_setup.bash
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/share/poco_vendor/local_setup.sh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/share/poco_vendor/local_setup.zsh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/local_setup.bash
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/local_setup.sh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/local_setup.zsh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/setup.bash
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/setup.sh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/setup.zsh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/poco_vendor/_order_packages.py
Failed packages: rcutils

The second time it is run, the build fails trying to link fastrtps with the following error:

...
[ 38%] Building C object src/cpp/CMakeFiles/fastrtps.dir/__/__/thirdparty/android-ifaddrs/ifaddrs.c.o
72 warnings generated.
73 warnings generated.
1 warning generated.
1 warning generated.
1 warning generated.
1 warning generated.
[ 39%] Linking CXX shared library libfastrtps.so
/home/johnmark/Android/Ndk/android-ndk-r17/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/bin/ld: error: cannot find -lfastcdr
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
src/cpp/CMakeFiles/fastrtps.dir/build.make:1403: recipe for target 'src/cpp/libfastrtps.so' failed
make[2]: *** [src/cpp/libfastrtps.so] Error 1
CMakeFiles/Makefile2:85: recipe for target 'src/cpp/CMakeFiles/fastrtps.dir/all' failed
make[1]: *** [src/cpp/CMakeFiles/fastrtps.dir/all] Error 2
Makefile:151: recipe for target 'all' failed
make: *** [all] Error 2

<== Command '. /home/johnmark/code/ros2_android/build_isolated/fastrtps/cmake__build.sh && /usr/bin/make -j8 -l8' failed in '/home/johnmark/code/ros2_android/build_isolated/fastrtps' with exit code '2'
Failed packages: rcutils

The third time I get:

...
-- Up-to-date: /home/johnmark/code/ros2_android/install_isolated/rosidl_parser/share/rosidl_parser/package.xml
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/rosidl_parser/local_setup.bash
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/rosidl_parser/local_setup.sh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/rosidl_parser/local_setup.zsh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/rosidl_parser/setup.bash
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/rosidl_parser/setup.sh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/rosidl_parser/setup.zsh
-- [ament] Deploying: /home/johnmark/code/ros2_android/install_isolated/rosidl_parser/_order_packages.py
CMake Error at CMakeLists.txt:7 (find_package):
  By not providing "Findament_cmake_export_jars.cmake" in CMAKE_MODULE_PATH
  this project has asked CMake to find a package configuration file provided
  by "ament_cmake_export_jars", but CMake did not find one.

  Could not find a package configuration file provided by
  "ament_cmake_export_jars" with any of the following names:

    ament_cmake_export_jarsConfig.cmake
    ament_cmake_export_jars-config.cmake

  Add the installation prefix of "ament_cmake_export_jars" to
  CMAKE_PREFIX_PATH or set "ament_cmake_export_jars_DIR" to a directory
  containing one of the above files.  If "ament_cmake_export_jars" provides a
  separate development package or SDK, be sure it has been installed.


-- Configuring incomplete, errors occurred!
See also "/home/johnmark/code/ros2_android/build_isolated/rcljava_common/CMakeFiles/CMakeOutput.log".

<== Command '. /home/johnmark/code/ros2_android/build_isolated/rcljava_common/cmake__build.sh && /usr/local/bin/cmake -DBUILD_TESTING=0 -DPYTHON_EXECUTABLE=/usr/bin/python3 -DCMAKE_TOOLCHAIN_FILE=/home/johnmark/Android/Ndk/android-ndk-r17/build/cmake/android.toolchain.cmake -DANDROID_FUNCTION_LEVEL_LINKING=OFF -DANDROID_NATIVE_API_LEVEL=android-21 -DANDROID_TOOLCHAIN_NAME=arm-linux-androideabi-clang -DANDROID_STL=gnustl_shared -DANDROID_ABI=armeabi-v7a -DANDROID_NDK=/home/johnmark/Android/Ndk/android-ndk-r17 -DTHIRDPARTY=ON -DCOMPILE_EXAMPLES=OFF '-DCMAKE_FIND_ROOT_PATH=/home/johnmark/code/ament_java/install_isolated;/home/johnmark/ros2_android/install_isolated' -DCMAKE_INSTALL_PREFIX=/home/johnmark/code/ros2_android/install_isolated/rcljava_common /home/johnmark/code/ros2_android/src/ros2_java/ros2_java/rcljava_common' failed in '/home/johnmark/code/ros2_android/build_isolated/rcljava_common' with exit code '1'
Failed packages: rcutils

Building for desktop Java works fine.

Edit: I thought the problem was trying to compile with examples on, but even without examples it fails

[esteve]

Thanks for trying out ros2_java and ros2_android!

The COMPILE_EXAMPLES flag controls whether the Fast-RTPS examples are built, which are not needed for Android. The .apks are in the ros2_android_examples repository, which are always built.

Can you paste a longer log with where rcutils failed?

Thanks for your prompt reply, here's the whole output of the script I posted (first run): https://pastebin.com/Kwt5hHUz

Edit:
More comprehensive log (I forgot to tee stderr last time)
https://pastebin.com/7NWFHhM0

Edit:
I've also tried with android NDK version r15c

[esteve]

Unfortunately --parallel makes the output a bit unclear, could you remove it so that packages are built sequentially? Thanks.

No problem. This time it causes the linker error (and is too long for pastebin)
https://gist.github.com/johnmarkwayve/a8b6ccf3069f076335bae882a211781e

[esteve]

That's weird, because Fast-RTPS fetches a local copy of Fast-CDR and link against it, so it shouldn't have any problem finding it. Sorry for all the trouble, but could you remove both workspaces and try from scratch and without --parallel? I think there were some files left over from the first CMake run that are causing the link error.

Thanks for all of your help. While I was waiting I did a fresh build of the ament package, desktop package, and android package in a completely different tree. I'm no longer seeing these errors, which suggests that something may have been messed up with my first ament package build. Sorry for the wild goose chase.

I'm still working through some errors (including the test_msgs thing mentioned in #35 ), but I will open them as separate issues if they need addressing.

Thanks again for your help.

[esteve]

Great to hear it worked! test_msgs is a bit special, so it's probably best to pass it to --skip-packages for now when crosscompiling. Let me know if there's anything I can help with. Shall I close this ticket or do you prefer to keep it open?

Feel free to close it. While I'm here, just a couple of suggestions for the README:

• Put in the --skip-packages test_msgs (or equivalent AMENT_IGNORE) to the android build instructions, with a sentence indicating why
• Note that the ANDROID_HOME environment variable needs to be defined and pointing at the root of the SDK distribution
• The repos at https://github.com/ros2java are behind the ones at https://github.com/esteve, but the readme there still refers to the repos at /esteve, this may cause some confusion/conflicts. Why are there two versions at all?

[esteve]

@johnmarkwayve thanks! I've updated the README (esteve@d6077dd). Let me know if there's anything else that needs to be improved/fixed.

The repos at https://github.com/ros2java are behind the ones at https://github.com/esteve, but the readme there still refers to the repos at /esteve, this may cause some confusion/conflicts. Why are there two versions at all?

The ros2java organization has a bit of an unfortunate history, a squatter registered it a while ago before me and forked my repositories there, so I had to ask GitHub to grant me access to it, I had forgotten about it since then. I just cleaned it and removed the repositories, thanks for the heads up.