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It seems that with catkin in Groovy,
find_package(catkin COMPONENTS roscpp std_msgs)
is equivalent to
find_package(catkin)
find_package(roscpp)
find_package(std_msgs)
Is there any difference?
As far as I understand they are equivalent.
The only difference is that find_package(catkin COMPONENTS roscpp std_msgs) will consolidate all of the COMPONENTS into the catkin_* CMake variables, for instance catkin_INCLUDE_DIRS will contain roscpp_INCLUDE_DIRS and std_msgs_INCLUDE_DIRS.
I could have checked the docs: http://ros.org/wiki/catkin/CMakeLists.txt
Though it may be obvious from William's response, using the first method is more convenient and actually recommended. the consequence of using the latter is that all of the CMake functions/macros that utilize environment variables generated by find_package() have to have the corresponding variable listed as an argument. For C++ code, this particularly effects include_directories() and target_link_libraries(). Example:
Instead of :
include_directories(${catkin_INCLUDE_DIRS})
add_executable(foo ...)
target_link_libraries(foo ${catkin_LIBRARIES})
You would have:
include_directories(${catkin_INCLUDE_DIRS} ${roscpp_INCLUDE_DIRS} ${std_msgs_INCLUDE_DIRS})
add_executable(foo ...)
target_link_libraries(foo ${catkin_LIBRARIES} ${roscpp_LIBRARIES} ${std_msgs_LIBRARIES})
So save yourself effort and always find catkin packages as components of catkin!
Asked: 2012-11-12 08:26:45 -0500
Seen: 2,321 times
Last updated: Jun 17 '16
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Follow up question: How does CMake know to look for the .cmake config files in the /opt/ros/ directory?