Some problems about creating my first msg

I’m a beginner of ros, I met a problems about creating my first topic.
The flowing is the problem,it just a warning,the real error is that the cmake can not find the *.h which I had included in my *.cpp, but I think it had a relation with this waring :
“Policy CMP0046 is not set: Error on non-existent dependency in add_dependencies.”
Is it the problem of Cmake’s version ? How can I solve it ?
my Cmake version is 2.8.3

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 for an explanation. This is only a warning. To write your first message, you can follow this tutorial. Take a close look at the CMakeLists.txt part of the tutorial.

Please ask such questions on http://answers.ros.org following the support guidelines: http://wiki.ros.org/Support.

ROS Discourse is for news and general interest discussions. ROS Answers provides a forum which can be filtered by tags to make sure the relevant people can find and/or answer the question, and not overload everyone with hundreds of posts.

Additionally, when you ask questions be sure to include as much information as possible. In this case that would include your CMakeLists.txt file.