title: Getting undefined reference error at adding simple class to library
body: <p>I am working with a rather sizeable library which uses CMake for compilation/linking. I need to add some functionality, thus I need to add some classes to the library. The problem is that when I add even a simple helloWorld class to the library, and try to call it from some main function, I get undefined reference problem at link time. When I looked into the built code ("CMakeFiles" within the library folder), my class hasn't been compiled by CMake (and thus, for instance, there is no HelloWorld.o file in there). </p>
  
  <p>Can somebody point out where I am going wrong? Do I need to explicitely tell CMake to compile this class? (if yes, how?). I am novice in CMake, so don't know how to tackle this problem.</p>
  
  <p>I call the function like this.
  ``</p>
  
  <pre><code>GSROrdinary sord;
  </code></pre>
  
  <p>The error message, I get, is something like this.</p>
  
  <pre><code>undefined reference to beep::GSROrdinary::GSROrdinary()
  undefined reference to beep::GSROrdinary::~GSROrdinary()
  </code></pre>