title: Structs that refer to each other
body: <p>I want to have two structs that can contain each other. Here is an example:</p>
  
  <pre><code>struct a {
    struct b bb;
  };
  
  struct b {
    struct a aa;
  };
  </code></pre>
  
  <p>But this code doesn't compile. gcc says:</p>
  
  <pre><code>test.c:3: error: field ‘bb’ has incomplete type
  </code></pre>
  
  <p>Is there a way to achieve this?</p>