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, 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 # ifndef NAN 29 # define NAN (__builtin_nanf ("")) 30 # endif 31 32 #elif defined __GNUC__ 33 34 # define NAN \ 35 (__extension__ \ 36 ((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; }) \ 37 { __l: 0x7fc00000UL }).__d) 38 39 #else 40 41 # include <endian.h> 42 43 # if __BYTE_ORDER == __BIG_ENDIAN 44 # define __nan_bytes { 0x7f, 0xc0, 0, 0 } 45 # endif 46 # if __BYTE_ORDER == __LITTLE_ENDIAN 47 # define __nan_bytes { 0, 0, 0xc0, 0x7f } 48 # endif 49 50 static union { unsigned char __c[4]; float __d; } __nan_union 51 __attribute_used__ = { __nan_bytes }; 52 # define NAN (__nan_union.__d) 53 54 #endif /* GCC. */ 55