this is a gcc file, you can download it and learn its usetility, for further detail please look at t

				/* Copyright (C) 2003 Free Software Foundation, Inc.  */								/* { dg-do preprocess } */				/* { dg-options "-c -include ${srcdir}/g++.dg/cpp/c++_cmd_1.h" } */								/* Contributed by Devang Patel    */								int main ()				{					return 0;				}