title: cpp syntax for CLICK modules
body: <p>I was just trying to work on some "click" cpp modules.
  I came accross this syntax</p>
  
  <pre><code>class SimpleQueue : public Element, public Storage { public:
  SimpleQueue() CLICK_COLD;
  int configure(Vector&lt;String&gt;&amp;, ErrorHandler*) CLICK_COLD;
  </code></pre>
  
  <p>I was wondering what is this syntax "<strong>CLICK_COLD</strong>"?</p>
  
  <p><a href="https://github.com/kohler/click/blob/master/elements/standard/simplequeue.hh" rel="nofollow noreferrer">https://github.com/kohler/click/blob/master/elements/standard/simplequeue.hh</a></p>
  
  <p>This is just one file. But there is more than one file which has this <strong>"CLICK_COLD"</strong> used every where. Not sure what is this syntax in cpp?</p>
  
  <p>In general I wanted to understand what is <strong>XYZ_YYY</strong> after any method or constructor mean in cpp?</p>