h a 
    // pointer.
    track_selectively = 1,
    // always track this type
    track_always = 2
};
</code></pre>
A corresponding macro is defined so that we can use:
<pre><code>
BOOST_CLASS_TRACKING(my_class, boost::serialization::track_never)
</code></pre>
Default tracking traits are:
<ul>
  <li>For primitive, <code style="white-space: normal">track_never</code>.
  <li>For pointers, <code style="white-space: normal">track_never</code>.
  That is, addresses of addresses are not tracked by default.
  <li>