title: Use super class's address/pointer in initialization list
body: <p>context 1:  class D : public B1, public B2{};</p>
  
  <p>context 2:  B2 takes B1 to initialize:  B2( B1 * ) //B2's constructor</p>
  
  <p>my question is in D's initialization list:</p>
  
  <p>D::D() : B1(), B2( ? )...  <strong>What should be in ?</strong></p>
  
  <p>I don't want to put " (B1*)this " in the ? place, because it's no good to use "this" in initialization list. And since B1 part has been initialized, it makes sense to use it.</p>
  
  <p>What should I do ?</p>