Unions to extract data
<p>Won't the union in <a href="http://stackoverflow.com/questions/943267/is-it-a-good-practice-to-use-unions-in-c">this</a> question cause UB when used as this:</p>

<pre><code>union Data
{
    unsigned int intValue;
    unsigned char argbBytes[4];
};
Data data;
data.intValue = 1235347;
unsigned char alpha = data.argbBytes[0]; //UB?
</code></pre>

<p>I'm thinking about 9.5/1 in the standard:</p>

<blockquote>
  <p>In a union, at most one of the data
  members can be active at any time,
  that is, the value of at most one of
  the data members can be stored in a
  union at any time.</p>
</blockquote>
