Linking with Gazebo using Catkin fails

Some of the exported flags (?) are being done incorrectly with Gazebo when using Catkin. @j-rivero indicates the problem is not within Gazebo because “We have built a lot of third party software on top of Gazebo so it should be related to catkin packages somehow.” Though, we’ve also built even more software with Catkin…

The original issue from bitbucket:

Based on discussions with @j-rivero on this gazebo_ros_pkgs pull request, I’ve isolated some sort of flag export build problem that results in the error:

CMake Error at /home/dave/ros/current/ws_gazebo_test/devel_release/share/base_pkg/cmake/base_pkgConfig.cmake:141 (message):
  Project 'dummy_pkg' tried to find library '-lpthread'.  The library is
  neither a target nor built/installed properly.  Did you compile project
  'base_pkg'? Did you find_package() it before the subdirectory containing
  its code is included?
Call Stack (most recent call first):
  /opt/ros/kinetic/share/catkin/cmake/catkinConfig.cmake:76 (find_package)
  CMakeLists.txt:6 (find_package)

I think the problem is Gazebo7 is exporting a dependency on pthread which is suggested is bad on StackOverflow.

This occurs when one catkin package depends on Gazebo, and another depends on that package:

base_pkg CMakeLists

cmake_minimum_required(VERSION 2.8.3)
project(base_pkg)

find_package(catkin REQUIRED COMPONENTS
  roscpp
)

find_package(GAZEBO REQUIRED)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${GAZEBO_CXX_FLAGS}")

find_package(Boost REQUIRED COMPONENTS thread)

include_directories(
  ${catkin_INCLUDE_DIRS}
)

catkin_package(
  DEPENDS
    Boost
    GAZEBO
)

dependent pkg CMakeLists

cmake_minimum_required(VERSION 2.8.3)
project(dummy_pkg)

find_package(catkin REQUIRED COMPONENTS
  base_pkg
)

include_directories(
  ${catkin_INCLUDE_DIRS}
)

catkin_package(
  CATKIN_DEPENDS
    base_pkg
)

The full workspace can be tested from this barebones test repo I’ve just created.

[dirk-thomas]

I will close this for now since it is not planned to change the behavior of the catkin API atm.

[jlack1987]

Would just like to toss in here that I ran into the same problem independently when trying to link protobuf w/o gazebo. We already forked our own FindProtobuf.cmake file, so I just commented out the chunk that added -lpthread to the libraries and that took care of it. I really appreciate the detailed research done here, saved me a ton of time.