1 /* `NAN' constant for IEEE 754 machines.
2 Copyright (C) 1992,1996,1997,1999,2004,2006 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, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
18 02111-1307 USA. */
19
20 #ifndef _MATH_H
21 # error "Never use <bits/nan.h> directly; include <math.h> instead."
22 #endif
23
24
25 /* IEEE Not A Number. */
26
27 #if __GNUC_PREREQ(3,3)
28
29 # define NAN (__builtin_nanf (""))
30
31 #elif defined __GNUC__
32
33 # define NAN \
34 (__extension__ \
35 ((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; }) \
36 { __l: 0x7fc00000UL }).__d)
37
38 #else
39
40 # include <endian.h>
41
42 # if __BYTE_ORDER == __BIG_ENDIAN
43 # define __nan_bytes { 0x7f, 0xc0, 0, 0 }
44 # endif
45 # if __BYTE_ORDER == __LITTLE_ENDIAN
46 # define __nan_bytes { 0, 0, 0xc0, 0x7f }
47 # endif
48
49 static union { unsigned char __c[4]; float __d; } __nan_union
50 __attribute_used__ = { __nan_bytes };
51 # define NAN (__nan_union.__d)
52
53 #endif /* GCC. */
54