Add ros cmake to an already existing cmake - c++

Question

I have a really big code with this cmake that works:
cmake_minimum_required(VERSION 2.8 FATAL_ERROR)
project(MYPROJECT)
set (CMAKE_CXX_STANDARD 11)
find_package(PCL 1.7 REQUIRED)
if(DEFINED PCL_LIBRARIES)
list(REMOVE_ITEM PCL_LIBRARIES "vtkproj4")
endif()
FIND_PACKAGE(Boost COMPONENTS program_options REQUIRED)
include_directories(${PCL_INCLUDE_DIRS})
INCLUDE_DIRECTORIES(${Boost_INCLUDE_DIRS})
link_directories(${PCL_LIBRARY_DIRS})
add_definitions(${PCL_DEFINITIONS})
add_executable (main src/main.cpp)
target_link_libraries (main ${PCL_LIBRARIES})
Now, I want to publish the results of this code to a ros topic. So I added this code to a ros workspace, and need to add ros stuff into the cmake. I changed the project name to the pkg name, and added to the cmake the find_package, include_directories and catkin_package, ending with this CMake:
cmake_minimum_required(VERSION 2.8 FATAL_ERROR)
project(plc)
set (CMAKE_CXX_STANDARD 11)
find_package(PCL 1.7 REQUIRED)
if(DEFINED PCL_LIBRARIES)
list(REMOVE_ITEM PCL_LIBRARIES "vtkproj4")
endif()
find_package(catkin REQUIRED COMPONENTS
pcl_conversions
pcl_ros
roscpp
)
FIND_PACKAGE(Boost COMPONENTS program_options REQUIRED)
include_directories(${catkin_INCLUDE_DIRS})
include_directories(${PCL_INCLUDE_DIRS})
INCLUDE_DIRECTORIES(${Boost_INCLUDE_DIRS})
link_directories(${PCL_LIBRARY_DIRS})
add_definitions(${PCL_DEFINITIONS})
catkin_package(CATKIN_DEPENDS roscpp pcl_ros pcl_conversions)
add_executable (main src/main.cpp)
target_link_libraries (main ${PCL_LIBRARIES})
also added this to the package.xml:
<build_depend>pcl_conversions</build_depend>
<build_depend>pcl_ros</build_depend>
<build_depend>roscpp</build_depend>
<build_export_depend>pcl_conversions</build_export_depend>
<build_export_depend>pcl_ros</build_export_depend>
<build_export_depend>roscpp</build_export_depend>
<exec_depend>pcl_conversions</exec_depend>
<exec_depend>pcl_ros</exec_depend>
<exec_depend>roscpp</exec_depend>
But I keep getting this errors, that according to google means that I made the CMake wrong.
usr/bin/ld: main.cpp:(.text+0x6bdc): undefined reference to `ros::Rate::Rate(double)'
/usr/bin/ld: main.cpp:(.text+0x6beb): undefined reference to `ros::NodeHandle::ok() const'
/usr/bin/ld: main.cpp:(.text+0x6c07): undefined reference to `ros::Time::now()'
/usr/bin/ld: main.cpp:(.text+0x6c3e): undefined reference to `ros::spinOnce()'
/usr/bin/ld: main.cpp:(.text+0x6c4d): undefined reference to `ros::Rate::sleep()'
/usr/bin/ld: main.cpp:(.text+0x6c5e): undefined reference to `ros::Publisher::~Publisher()'
/usr/bin/ld: main.cpp:(.text+0x6c6d): undefined reference to `ros::NodeHandle::~NodeHandle()'
/usr/bin/ld: main.cpp:(.text+0x6cfc): undefined reference to `ros::Publisher::~Publisher()'
/usr/bin/ld: main.cpp:(.text+0x6d0b): undefined reference to `ros::NodeHandle::~NodeHandle()'
Any idea how can I fix this? I'm clueless.
PS: I have another workspace with python ros that publishes/subscribes without problems, and this code was working perfectly before I added the ros part in cpp.

Answer 1

Make sure you also link agains the catkin specified libraries (${catkin_LIBRARIES}), because there the ROS libs are listed in:
target_link_libraries (main
${PCL_LIBRARIES})
${catkin_LIBRARIES}
)