title: Allocate a polymorphic class member at a specific location?
body: <p>I have a class with a few class members and a polymorphic member:</p>
  
  <pre><code>class Container{
  
      Container::Container(){ p = new Derived();}
  
      Poly* p;
      A a;
      B b;
  };
  </code></pre>
  
  <p>I would like to allocate the memory for the actual polymorphic object <code>Container::p</code> points to, contiguously after <code>Container::b</code>, rather than via the default <code>new()</code> and therefore <code>malloc()</code>. </p>
  
  <p>What is the best way to achieve this?</p>