title: What is the usage of DEBUG_NEW and __FILE__?
body: <p>I saw the follow macros,</p>
  
  <pre><code>#ifdef _DEBUG
  #define new DEBUG_NEW
  #UNDEF THIS_FILE
  static char THIS_FILE[] = __FILE__;
  #endif
  </code></pre>
  
  <p>What is the usage of above macro?</p>
  
  <p>Thank you</p>