title: How to override fprintf in the C library? How to add GCC option to toplevel CMakeLists.txt?
body: <p>I know how to overwrite C-lib functions in just simple sample. But what I need is IN A REAL PROJECT which has hundreds of files that call fprintf.</p>
  
  <p>In each file, there's a <code>"#include &lt; stdio.h &gt;"</code>, and tens or hundreds of calls of <code>fprintf</code>. I wanna make all these fprintf to do my own job. I cannot remove the <code>"stdio.h"</code> and put a <code>"#include &lt; myprint.h &gt;"</code>, where <code>myprint.h</code> defines the real function or macro of <code>fprintf</code> that do my own job. <code>"stdio.h"</code> has many other calls in the project. I want a simple enough solution.</p>
  
  <p>Thanks!</p>
  
  <p>Do I make my question clear enough?...</p>
  
  <p>Update on 2014.03.08:
  Salute to all women at first...</p>
  
  <p>Please see my 2nd post below.</p>