I don't think that the warning and the error are related. The warning is about a CMake policy that is not set. See the [documentation](https://cmake.org/cmake/help/v3.0/policy/CMP0046.html) for an explanation. This is only a warning. To write your first message, you can follow [this](http://wiki.ros.org/ROS/Tutorials/WritingPublisherSubscriber%28c%2B%2B%29) tutorial. Take a close look at the CMakeLists.txt part of the tutorial. --- [Visit Topic](https://discourse.ros.org/t/some-problems-about-creating-my-first-msg/4780/2) or reply to this email to respond. If you do not want to receive messages from ros-users please use the unsubscribe link below. If you use the one above, you will stop all of ros-users from receiving updates. ______________________________________________________________________________ ros-users mailing list ros-users@lists.ros.org http://lists.ros.org/mailman/listinfo/ros-users Unsubscribe: