title: Detect ICC vs GCC at compile time
body: <p>How to detect at compile time if I'm using gcc or icc?</p>
  
  <p>(I was quite puzzled to find out that icc defines <code>__GNUC__</code> -- and even <code>__GNUC_MINOR__</code> and <code>__GNUC_PATCHLEVEL__</code> ! why?)</p>