title: definition of off_t with c99
body: <p>I'm trying to port some code from windows to linux, but I'm having difficulty with support for large files. off_t seems to be defined when gcc is run with -std=c89 but not for -std=c99. Even a trivial test case will not compile:</p>
  
  <pre><code>#define _LARGEFILE_SOURCE
  #define _LARGEFILE64_SOURCE
  #define _FILE_OFFSET_BITS 64
  #include &lt;stdio.h&gt;
  
  int main()
  {
      off_t x = 0;
      return 0;
  }
  </code></pre>
  
  <p>It really doesn't seem like this should be difficult (in fact, it's not on all other operating systems). Anyone have any idea what is happening?</p>