title: unsigned-signed underflow mechanism
body: <p>I know that the following</p>
  
  <pre><code>unsigned short b=-5u;
  </code></pre>
  
  <p>evaluates to b being 65531 due to an underflow, but I don't understand if 5u is converted to a signed int before being transformed into -5 and then re-converted back to unsigned to be stored in b or -5u is equal to 0 - 5u (this should not be the case, -x is a unary operator)</p>