1    	/* `NAN' constant for IEEE 754 machines.
2    	   Copyright (C) 1992-2015 Free Software Foundation, Inc.
3    	   This file is part of the GNU C Library.
4    	
5    	   The GNU C Library is free software; you can redistribute it and/or
6    	   modify it under the terms of the GNU Lesser General Public
7    	   License as published by the Free Software Foundation; either
8    	   version 2.1 of the License, or (at your option) any later version.
9    	
10   	   The GNU C Library is distributed in the hope that it will be useful,
11   	   but WITHOUT ANY WARRANTY; without even the implied warranty of
12   	   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   	   Lesser General Public License for more details.
14   	
15   	   You should have received a copy of the GNU Lesser General Public
16   	   License along with the GNU C Library; if not, see
17   	   <http://www.gnu.org/licenses/>.  */
18   	
19   	#ifndef _MATH_H
20   	# error "Never use <bits/nan.h> directly; include <math.h> instead."
21   	#endif
22   	
23   	
24   	/* IEEE Not A Number.  */
25   	
26   	#if __GNUC_PREREQ(3,3)
27   	
28   	# define NAN	(__builtin_nanf (""))
29   	
30   	#elif defined __GNUC__
31   	
32   	# define NAN \
33   	  (__extension__							      \
34   	   ((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; })  \
35   	    { __l: 0x7fc00000UL }).__d)
36   	
37   	#else
38   	
39   	# include <endian.h>
40   	
41   	# if __BYTE_ORDER == __BIG_ENDIAN
42   	#  define __qnan_bytes		{ 0x7f, 0xc0, 0, 0 }
43   	# endif
44   	# if __BYTE_ORDER == __LITTLE_ENDIAN
45   	#  define __qnan_bytes		{ 0, 0, 0xc0, 0x7f }
46   	# endif
47   	
48   	static union { unsigned char __c[4]; float __d; } __qnan_union
49   	  __attribute__ ((__unused__)) = { __qnan_bytes };
50   	# define NAN	(__qnan_union.__d)
51   	
52   	#endif	/* GCC.  */
53