title: Qt, windows and _POSIX_
body: <p>I'm working on building Qt 4.8.1 in VisualStudio 2005 and I was getting an issue that the compiler could not find <code>_fileno</code>.</p>
  
  <p>After some research, I found that in stdio.h it has</p>
  
  <pre><code>#ifdef  _POSIX_
  _CRTIMP __checkReturn int __cdecl fileno(__in FILE * _File);
  #else
  _CRTIMP __checkReturn int __cdecl _fileno(__in FILE * _File);
  #endif
  </code></pre>
  
  <p>I then looked through the qt code and found that qfsfilengine_win.cpp and qfilesystemengine_win.cpp both have</p>
  
  <pre><code>#define _POSIX_
  </code></pre>
  
  <p>It seems to me that this would be a mistake, and if I remove these lines, it seems to build successfully.</p>
  
  <p>Does anyone know why these files would be defining <code>_POSIX_</code>?</p>
  
  <p>Thanks.</p>