Hello,

Compiling my project directly on my raspberry has a high failure rate so I thought the cross compilation was a good option to avoid that. But it appears to be more difficult than I thought and there are not that much tutorials on the internet about this topic.

Can somebody help me figure it out by describing how to proceed step by step not to miss anything ?

Here's what I did : (this answer from stackoverflow helped me a lot)

1) Install the compiler for the raspberry on my computer (running Ubuntu 16.04) -> for my raspberry it's arm-linux-gnueabihf

2) Create a rostoolchain.cmake file :

SET(CMAKE_SYSTEM_NAME Linux)
SET(CMAKE_SYSTEM_VERSION 1)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

#avoid RT_LIBRARY-NOT-FOUND issue
set(CMAKE_LIBRARY_ARCHITECTURE arm-linux-gnueabihf)

#set(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
#set(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)

set(LD_LIBRARY_PATH ${LD_LIBRARY_PATH}
  $ENV{HOME}/raspberrypi/devel/lib)

set(PKG_CONFIG_PATH ${PKG_CONFIG_PATH}
  $ENV{HOME}/raspberrypi/devel/lib/pkgconfig)

# specify the cross compiler
SET(CMAKE_C_COMPILER   /usr/bin/arm-linux-gnueabihf-gcc)
SET(CMAKE_CXX_COMPILER /usr/bin/arm-linux-gnueabihf-g++)

SET(CMAKE_FIND_ROOT_PATH $ENV{HOME}/raspberrypi/rootfs)

SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)


set(CMAKE_LIBRARY_PATH
  $ENV{HOME}/raspberrypi/rootfs)


# Set compiler flag
SET(CMAKE_C_FLAGS "${CMAKE_CXX_FLAGS} --sysroot=${CMAKE_FIND_ROOT_PATH}")
SET( CMAKE_CXX_FLAGS  "${CMAKE_CXX_FLAGS} --sysroot=${CMAKE_FIND_ROOT_PATH}" )

3) Create a catkin profile to cross compile :

Profile:                     cross
Extending:        [explicit] /opt/ros/kinetic
Workspace:                   /home/robotics/raspberrypi
-------------------------------------------------------------------------------------------------------------------------
Source Space:       [exists] /home/robotics/raspberrypi/src
Log Space:          [exists] /home/robotics/raspberrypi/logs
Build Space:        [exists] /home/robotics/raspberrypi/build
Devel Space:        [exists] /home/robotics/raspberrypi/devel
Install Space:      [unused] /home/robotics/raspberrypi/install
DESTDIR:            [unused] None
-------------------------------------------------------------------------------------------------------------------------
Devel Space Layout:          linked
Install Space Layout:        None
-------------------------------------------------------------------------------------------------------------------------
Additional CMake Args:       -DBUILD_SHARED_LIBS=Off -DCMAKE_TOOLCHAIN_FILE=/home/robotics/raspberrypi/rostoolchain.cmake
Additional Make Args:        None
Additional catkin Make Args: None
Internal Make Job Server:    True
Cache Job Environments:      False
-------------------------------------------------------------------------------------------------------------------------
Whitelisted Packages:        None
Blacklisted Packages:        None

4) Finally, run catkin build but it generates this warning (I display for only one package) :

Warnings   << tile_manager:cmake /home/robotics/raspberrypi/logs/tile_manager/build.cmake.001.log                                                                                                          
CMake Warning at /home/robotics/raspberrypi/src/tile_manager/CMakeLists.txt:79 (add_executable):
  Cannot generate a safe linker search path for target tile_marker_node
  because there is a cycle in the constraint graph:

    dir 0 is [/home/robotics/raspberrypi/rootfs/usr/lib/arm-linux-gnueabihf]
      dir 1 must precede it due to link library [libpthread.so]
    dir 1 is [/usr/lib/x86_64-linux-gnu]
      dir 0 must precede it due to link library [libpthread.so]

  Some of these libraries may not be found correctly.

Leading to this error :

Errors     << tile_manager:make /home/robotics/raspberrypi/logs/tile_manager/build.make.002.log                                                                                                            
/opt/ros/kinetic/lib/libtf.so: file not recognized: File format not recognized
collect2: error: ld returned 1 exit status

It seems that there is a conflict with the paths /usr/lib/x86_64-linux-gnu, /home/robotics/raspberrypi/rootfs/usr/lib/arm-linux-gnueabihf and I have other warnings with /opt/ros/kinetic/lib too but I can't find which variable is defining those paths (I think I should only have /home/robotics/raspberrypi/rootfs/usr/lib/arm-linux-gnueabihf )

Am I missing something here or is it possible that the issues come from my CMakeLists.txt files ?

Any insight would be greatly appreciated.