title: Modify printf()s via macro to include file and line number information
body: <p>I was just wondering if there is some macro-hack we can use, to alter existing printf() statements in a project.</p>
  
  <pre><code>/* file.c */
  printf ("%s", strerror(errno));
  
  /* After macro processing, this line would become */
  printf ("%s %s %d", strerror(errno), __FILE__, __LINE__);
  </code></pre>