Linking external headers file in ROS package

asked 2017-09-06 14:12:57 -0600

rabee
3 ●1 ●1 ●2

I am trying to use the Kilobot simulator Kilombo with a ROS package. I am installing Kilombo as normal as a system library. I am then trying to include the Kilombo header file inside the ROS package to create a Kilombo simulation. The CMakeLists.txt of Kilombo looks like this:

add_library(sim display.c skilobot.c kbapi.c params.c stateio.c runsim.c neighbors.c distribution.c gfx/SDL_framerate.c gfx/SDL_gfxPrimitives.c gfx/SDL_gfxBlitFunc.c gfx/SDL_rotozoom.c)

add_library(headless skilobot.c kbapi.c params.c stateio.c runsim.c neighbors.c distribution.c)
set_target_properties(headless PROPERTIES COMPILE_DEFINITIONS "SKILO_HEADLESS")

if(CMAKE_COMPILER_IS_GNUCXX)
    add_definitions(-std=c99)
    add_definitions("-Wall -O2 -g")
#    add_definitions("-Wall -O3 -march=native -g")  
endif()

INSTALL(TARGETS sim headless
  ARCHIVE DESTINATION lib
)

INSTALL(FILES kilombo.h DESTINATION include)

INSTALL(FILES kilolib.h message.h message_crc.h params.h skilobot.h
    DESTINATION include/kilombo)

add_subdirectory(tests)

The CMakeLists.txt of the ROS package I am creating looks like this:

cmake_minimum_required(VERSION 2.8.3)
project(Kilombo_test)
find_package(catkin REQUIRED roscpp std_msgs)
if(CMAKE_COMPILER_IS_GNUCXX)
    add_definitions(-std=c99)
    add_definitions("-Wall -O2 -g")
endif()
include_directories(/usr/local/include /usr/local/lib)
link_directories(/usr/local/include)
add_executable(generated_test orbit.c)
target_link_libraries(generated_test ${catkin_LIBRARIES})

I include the Kilombo header files just as normal: #include <kilombo.h>

However, when I run catkin_make, I get many "undefined reference" errors. Some of those messages are:

orbit.c:53 undefined reference to 'kilo_turn_left'
orbit.c:53 undefined reference to 'set_motors'

These messages are shown after the commands:

####
#### Running command: "make -j2 -l2" in "/home/viki/catkin_ws/build"
####
Linking C executable generated_test

Both, kilo_turn_left and the function set_motors is defined in "kilolib.h" which itself is included in "kilombo.h".

Everything works fine if try running the simulation normally and not as a ROS package. The Makefile when I try to run it normally looks like the following. I have removed the parts which compiled for the real bot and not for the simulation.

SOURCES=orbit.c 
EXECUTABLE=orbit

# path of kilombo.h distributed with the simulator but also needed
# when compiling the user program for the real kilobot (avr-gcc has different default paths)
SIMHEADERS=/usr/local/include

#path to kilolib.a in the official kilolib, needed for real bots only
KILOLIB    =$(KILOHEADERS)/build/kilolib.a

SIM_CFLAGS = -c -g -O2 -Wall -std=c99  

SIM_LFLAGS = -lsim -lSDL -lm -ljansson
sim: $(EXECUTABLE)
hex: $(EXECUTABLE).hex
all: sim hex

clean :
    rm *.o $(EXECUTABLE) *.elf *.hex

However, when running a simulation as a ROS package, we need to define a CMakeLists.txt which is what I am having trouble with. What exactly am I doing wrong? I know there are many similar questions on this board but I have not been able to find a solution to my problem in those questions (though I believe I have gotten closer to the solution)

answered 2017-09-06 14:16:39 -0600

gvdhoorn
86574 ●283 ●1432 ●1054 http://cor.tudelft.nl/

updated 2017-09-06 14:38:12 -0600

This is a linking problem (ie: libraries), not a problem with headers.

add_executable(generated_test orbit.c)
target_link_libraries(generated_test ${catkin_LIBRARIES})

You're not linking any of the kilo* libraries, which is why the compiler cannot resolve the symbols.

You'll have to add one (or both? I don't know these libraries) of the sim or headless libs to the target_link_library(..) statement that you already have.

However: note that you are compiling C here: ROS has no client library for C, so you'll have to write something in C++. If/when you do, know that C++ mangles names, so you'll have to take care of that as well. You should get sufficient results if you search for c++ link c library with your favourite search engine.

Edit: some suggestions / questions:

/usr/local/lib should already be on the link path, and /usr/local/include should already be on the include path, so I don't believe you need to add those
putting /usr/local/include on the linker path seems rather strange to me: do you have libraries in that directory?
the same for /usr/local/lib on the include path: headers in a lib dir?
CMAKE_COMPILER_IS_GNUCXX is set if the compiler is g++, but -std=c99 is something for the C compiler. Should that be CMAKE_COMPILER_IS_GNUC in the conditional?

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Comments

Note btw that this is not a ROS problem, but really a missing statement in your CMake file.

gvdhoorn ( 2017-09-06 14:17:07 -0600 )edit

Then perhaps you coudl answer here ;) https://stackoverflow.com/questions/4...

rabee ( 2017-09-06 14:20:18 -0600 )edit

No, I won't. And this is a classic example of why you should avoid cross-posting questions like this. It leads exactly to this sort of duplicated effort. You've basically now received the same answer twice, in two different places ..

gvdhoorn ( 2017-09-06 14:26:57 -0600 )edit

And additionally: this question has been asked multiple times already. Please use the search before asking new questions. See #q227146 and #q200205 fi.

gvdhoorn ( 2017-09-06 14:28:59 -0600 )edit

I didn't receive any answers on that question. Which led me to think that perhaps it was a ROS-specific problem which is why I didn't receive any answers on stackoverflow. Which is why I posted here - after a significant wait on the other question.

rabee ( 2017-09-06 14:48:50 -0600 )edit

You're right, I'd missed the sept 3 posting date. My apologies. But even then, linking back to your other question and adding the "I think this is something specific to ROS, because .." would be good.

gvdhoorn ( 2017-09-06 14:50:56 -0600 )edit

No worries. Will do so. As to your suggestions:

Yes, those are superfluous, removing them had no effect
Again, not needed.
Once again, not needed.
Correct, fixed it.

As you pointed out, I needed to add the libraries in the in the target_link_library... statement. Thank you.

rabee ( 2017-09-06 15:45:36 -0600 )edit

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