Fix atomic error on loongarch64

[zhaixiaojuan]

Describe the bug
When I compile the project on a debian loongarch64 environment, I get an atomic-related error.

To Reproduce
The problem can be reproduced by executing the following command on Debian loongarch64 platform:
colcon build --symlink-install

Expected behavior
When I build the project on a Debian loongarch64 platform, I get an error:

Finished <<< controller_manager_msgs [1.27s]
--- stderr: hardware_interface
/usr/bin/ld: /opt/ros/jazzy/lib/libpal_statistics.so: undefined reference to `__atomic_store_16'
/usr/bin/ld: /opt/ros/jazzy/lib/libpal_statistics.so: undefined reference to `__atomic_load_16'
/usr/bin/ld: /opt/ros/jazzy/lib/libpal_statistics.so: undefined reference to `__atomic_compare_exchange_16'
collect2: error: ld returned 1 exit status

Environment
OS：debian
Version: trixie
System Architecture: LoongArch

Solution
I created a patch for this issue and verified it locally:
zhaixiaojuan@a4cbc33

Additional context
The LoongArch architecture (LoongArch) is an Instruction Set Architecture (ISA) that has a RISC style.
Documentations:
ISA:
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html
ABI:
https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html
More docs can be found at:
https://loongson.github.io/LoongArch-Documentation/README-EN.html

[christophfroehlich]

Isn't target_link_libraries working, like we did here?
https://github.com/ros-controls/realtime_tools/blob/master/realtime_tools%2FCMakeLists.txt

I also saw that we have some #include missing here in this repo. Could you please open a PR targeting master branch? we can backport this later to jazzy if needed.

[zhaixiaojuan]

@christophfroehlich
Hi, thank you very much for your reply. I referred to the link https://github.com/ros-controls/realtime_tools/blob/master/realtime_tools%2FCMakeLists.txt and tried to use a method like target_link_libraries(test_controller_interface, atomic) in it, but this method did not solve the problem.

The error "/opt/ros/jazzy/lib/libpal_statistics.so: undefined reference to `__atomic_store_16'" indicates that the library libpal_statistics.so requires atomic. When using a command like target_link_libraries(test_controller_interface atomic) , the generated test_controller_interface.dir/link.txt file is as follows:

/usr/bin/c++ -Wl,--dependency-file=CMakeFiles/test_controller_interface.dir/link.d CMakeFiles/test_controller_interface.dir/test/test_controller_interface.cpp.o -o test_controller_interface  -Wl,-rpath,/cloud/zxj/github/zxj/ros2_control-bak/build/controller_interface:/cloud/zxj/github/zxj/ros2_control-bak/install/hardware_interface/lib:/cloud/zxj/github/zxj/ros2_control-bak/install/joint_limits/lib:/opt/ros/jazzy/lib:/opt/ros/jazzy/lib/loongarch64-linux-gnu gmock/libgmock_main.a gmock/libgmock.a libcontroller_interface.so -latomic -pthread ......
/opt/ros/jazzy/lib/librclcpp.so /opt/ros/jazzy/lib/librclcpp_lifecycle.so /opt/ros/jazzy/lib/libpal_statistics.so

The added -latomic is after libpal_statictics.so, still results in the same error.

I've submitted a PR on master and hope to get your review: #2536

Regarding your mention of missing #include libraries, I'm not sure which ones you're referring to. Could you please provide some guidance?

[christophfroehlich]

look for atomic in the repo and if it is properly included in every file.

[christophfroehlich]

and you try to patch pal_statistics CMakeLists? maybe this will also solve your issue

[zhaixiaojuan]

Hi, I have submitted the relevant PR to pal_statistics( pal-robotics/pal_statistics#20 ). I tested this locally, and after fixing only this issue in pal_statistics, I still got the error : "/opt/ros/jazzy/lib/libpal_statistics.so: undefined refer to `__atomic_load_16'" when building the project.