title: How can I quickly search all included header files in a project for a specific symbol?
body: <p>Here's a problem I've had recently that just HAS to be a common pain to others here.  </p>
  
  <p>I'm working with someone else's legacy C code and need to find where a function or macro was defined.  The code <code>#include</code>s a bunch of different standard system libraries in addition to those from the specific project. </p>
  
  <p>Is there a tool or technique to quickly find where a specific function, macro, (or other global for that matter) was defined?  </p>
  
  <p>I tried: </p>
  
  <pre><code>grep -R 'function' /usr/lib
  </code></pre>
  
  <p>and other similar *nix/bash-fu with only limited success and lots of annoying chaff to cull.  One of you sage coders out there must have a good solution to this seemingly common scenario.</p>
  
  <p>I was very surprised to not find another question on this particular pain here or in my searches of the interwebs.  (I'm sure there will be angry comments if I missed one... ;-))</p>
  
  <p>Thanks in advance for any tips!</p>