title: What does "expected in: flat namespace" mean?
body: <p>The OS X dynamic loader often gives errors like</p>
  
  <pre><code>Symbol not found: &lt;some symbol name&gt;
  Referenced from: &lt;lib location&gt;
  Expected in: flat namespace
  </code></pre>
  
  <p>If you <a href="https://stackoverflow.com/search?q=expected+in+flat+namespace">search for the error</a> you'll find a ton of errors that have it. I understand roughly that the problem is an incorrect linking, but none of the answers explain what "flat namespace" means here, exactly. </p>