title: this of a calling object as a default argument C++
body: <p>I'm trying to create a C++ macro with a variable number of arguments (0 to 1) which will act as a wrapper to a function call in order to supply the this pointer of a calling object as a default argument value.</p>
  
  <p>So that the user could make the calls:</p>
  
  <pre><code>    CALL(pointer) // An argument is supplied, pass it to the call
      CALL()        // No argument supplied, pass the this pointer value instead
  </code></pre>