title: Use of selected_real_kind in Fortran to achieve desired minimum precision
body: <p>I am using gfortran 4.7.1 on Mac OS X 10.8 to compile a simple program using a specific precision:</p>
  
  <pre><code>program simple
    implicit none
    integer, parameter :: l = selected_real_kind(18,100)
    real(kind=l) :: myNum
    myNum = 0.123456789123456789
    print '(f18.12)', myNum
  end program simple
  </code></pre>
  
  <p>When I compile and run I get <code>0.123456791043</code> which obviously indicates I'm not getting the precision I called for.</p>
  
  <p>However if I compile with <code>-fdefault-real-8</code> I get the right answer.  Obviously, I could just move on and use the option, but I can't help wondering whether this is a bug or I am missing some justification.  Do I really have to specify my real size outside of the code itself when it seems that <code>selected_real_kind</code> intent is to allow the code to specify precision?</p>