title: How to check if a section of C++ code is being compiled?
body: <p>I'm working in a pretty large codebase, and I don't really understand how the build system works. I added a C++ function into the code, but I get an undefined reference error at runtime, which tells me the part I added may not be getting compiled.</p>
  <p>I am wondering how I can check if a particular part of a file is being compiled or not?</p>