title: std::ignore for ignoring unused variable
body: <p>Is it a good approach to use <code>std::ignore</code> for ignoring unused variables?</p>
  
  <p>Suppose I have a function like this:  </p>
  
  <pre><code>void func(int i)
  {
     //for some reason, I don't need i anymore but I cannot change signature of function    
     std::ignore = i; 
  }
  </code></pre>
  
  <p><strong>Additional Info</strong></p>
  
  <p>This was one example and some answers suggested to use <em>anonymous</em> variables. But how would I do it for other cases, like: </p>
  
  <pre><code>int Thread_UnSafe_func_returnSomething():
  void func()
  {
     // To make it thread safe
     // Also it is required to call only once
     static int i = Thread_UnSafe_func_returnSomething();
  
     std::ignore = i;
  }
  </code></pre>