title: What does this C++ constructor in the initialization list mean?
body: <p>I found this C++ constructor that uses an initialization list I don't understand what this convention is. I do know this initialization list can be use to instantiate a member of a instance with a param, but I've never seen a class constructor called from a list.</p>
  <pre><code>// G inherits from H
  class GBackend : public HBackend {...}
  
  // Constructor for G
  // What is this HBackend constructor doing?
  GBackend::GBackend(const BackendOptions&amp; options) : HBackend(options), g_options(options) {...}
  
  </code></pre>