title: gdb print double pointer
body: <p>I have a <code>struct</code> as </p>
  
  <pre><code>typedef struct p {
      struct m **k;
      // ..other member
  } p_t;
  
  p_t *pi;
  </code></pre>
  
  <p>I need to access the value <code>pi-&gt;k[1]</code> through gdb.</p>