1/* `NAN' constant for IEEE 754 machines.
2 Copyright (C) 1992-2016 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
48static 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