title: What are the risks to massively forward declaration classes in header files?
body: <p>For every pointer <code>p1</code> of class <code>class1</code>, are there any risks we should consider by using a forward declaration of <code>class1</code> instead of including <code>class1</code> header file?</p>
  
  <p>I can see only the advantage: The header file will have less size.</p>