title: Warning: Unreferenced local variable
body: <p>When I provide a constructor for class A, I don't get the unreferenced local variable why?
  What does the empty constructor do to eliminate the warning?</p>
  
  <pre><code>class A
  {
  public:
     A() {}
  };
  
  int main()
  {
     A a;
  }
  </code></pre>