ROS2 cross-compilation

[lukicdarkoo]

I got a request to solve ROS2 cross-compilation issue. There are two possible solutions:

• QEMU + Docker. This is currently the official approach (https://index.ros.org/doc/ros2/Tutorials/Cross-compilation/#cross-compiling-ros-2), but there are multiple issues with this approach:
  • compilation time is long because of ARM emulation with QEMU,
  • cross_compile doesn't support custom sysroots or compiler toolchains (Use cross-compilers to compile workspace instead of an emulated compilation ros-tooling/cross_compile#69) and
  • there are multiple non-resolved overheads in Docker images supplied with cross_compile (e.g. Allow user to skip rosdep collection ros-tooling/cross_compile#140 and Provide base Docker images for download instead of building locally ros-tooling/cross_compile#141)
• Regular cross-compilation. This can be complicated to configure for regular users since they would need to e.g. build Crosstool-NG, build a toolchain, probably patch multiple ROS2 packages...

However, ROS Tooling group works on putting cross-compilation tools in Docker image (ros-tooling/cross_compile#69). From my point of view, this is the ultimate solution! A user would install our container with toolchain simply with docker pull OUR_CONTAINER, allocate a pseudo-tty (docker run -it) and run any build command at native speed. If successful, we could merge the solution with cross_compile.

A few resources to start with:

• https://tttapa.github.io/Pages/Raspberry-Pi/C++-Development/Building-The-Toolchain.html
• https://blog.kitware.com/cross-compiling-for-raspberry-pi/