title: size of a datatype without using sizeof
body: <p>I have a data type, say <code>X</code>, and I want to know its size without declaring a variable or pointer of that type and of course without using <code>sizeof</code> operator.</p>
  
  <p>Is this possible? I thought of using standard header files which contain size and range of data types but that doesn't work with user defined data type.</p>