title: O_DIRECT undeclared, Eclipse CDT, Ubuntu 20.04
body: <p>I am experiencing an issue with O_DIRECT.
  I am trying to use it with <code>open()</code>, but I get an error like:</p>
  
  <pre><code>error: O_DIRECT undeclared (first use in this function)
  </code></pre>
  
  <p>I am including <code>&lt;fcntl.h&gt;</code></p>
  
  <p>I grepped <code>/usr/include/</code> directory for <code>O_DIRECT</code> and it exists in <code>x86_64-linux-gnu/bits/fcntl-linux.h</code>. I tried to include this file instead, but then I get this error:</p>
  
  <pre><code>error: #error Never use &lt;x86_64-linux-gnu/bits/fcntl-linux.h&gt; directly; include &lt;fcntl.h&gt; instead.
  </code></pre>
  
  <p>I am trying to all of this in Eclipse CDT project on newly installed Ubuntu 20.04 system.</p>