title: How do I handle "warning: use of ‘auto’ in parameter declaration only available with -fconcepts"
body: <p>This is the code that cause the warning:</p>
  
  <pre><code>inline auto getclock() { return std::chrono::steady_clock::now(); }
  inline auto getelapsed(auto b, auto e) { return std::chrono::duration_cast&lt;std::chrono::nanoseconds&gt;(e-b).count(); }
  //USAGE: auto b=getclock(); some_func_to_be_timed(...); auto duration=getelapsed(b, getclock()); ..
  </code></pre>
  
  <p>This code compiled without problem  before I recently upgraded to gcc 8 (c++17), now I get the warning as stated in the question.
  Why would I get this warning now, and how should I handle it?</p>
  
  <p>PS: I don't use concepts (explicitly) anywhere in the rest of the code.</p>