title: How does the control block of a shared pointer behave with const shared pointers
body: <pre><code>const std::shared_ptr&lt;int&gt; x (new int (2));
  const std::shared_ptr&lt;int&gt; y (x);
  </code></pre>
  
  <p>copying a shared pointer makes changes to the control block where the 'const' shared pointers point to, does that not contradict the constness part? </p>