title: Empty value in explicit copy constructor with member initialization list
body: <p>Consider this copy constructor:</p>
  
  <pre><code>myclass::myclass(const myclass&amp; rhs):
    _a(rhs._a), _b() {
  }
  </code></pre>
  
  <p>Assuming _b is defined as:</p>
  
  <pre><code>int _b[100];
  </code></pre>
  
  <p>What would <code>_b</code> get initialized to? What is the difference between writing <code>_b()</code> vs not including <code>_b</code> in the list at all?</p>