title: What does the tilde (~) in macros mean?
body: <p>Seen on <a href="https://gustedt.wordpress.com/2010/06/08/detect-empty-macro-arguments/" rel="noreferrer">this site</a>, the code shows macro invocations using a tilde in parentheses:</p>
  
  <pre><code>HAS_COMMA(_TRIGGER_PARENTHESIS_ __VA_ARGS__ (~))
  //                                          ^^^
  </code></pre>
  
  <p>What does it mean / do? I suspect it to just be an empty argument, but I'm not sure. Is it maybe specific to C(99) like the <code>__VA_ARGS__</code> is specific to C99 and existent in C++?</p>