1 /* `NAN' constant for IEEE 754 machines. 2 Copyright (C) 1992, 1996, 1997, 1999, 2002, 2004 3 Free Software Foundation, Inc. 4 This file is part of the GNU C Library. 5 6 The GNU C Library is free software; you can redistribute it and/or 7 modify it under the terms of the GNU Lesser General Public 8 License as published by the Free Software Foundation; either 9 version 2.1 of the License, or (at your option) any later version. 10 11 The GNU C Library is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 Lesser General Public License for more details. 15 16 You should have received a copy of the GNU Lesser General Public 17 License along with the GNU C Library; if not, write to the Free 18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 19 02111-1307 USA. */ 20 21 #ifndef _MATH_H 22 # error "Never use <bits/nan.h> directly; include <math.h> instead." 23 #endif 24 25 26 /* IEEE Not A Number (QNaN). Note that MIPS has the QNaN and SNaN patterns 27 reversed compared to most other architectures. The IEEE spec left 28 the definition of this open to implementations, and for MIPS the top 29 bit of the mantissa must be SET to indicate a SNaN. */ 30 31 #if __GNUC_PREREQ(3,3) 32 33 # define NAN (__builtin_nanf("")) 34 35 #elif defined __GNUC__ 36 37 # define NAN \ 38 (__extension__ \ 39 ((union { unsigned __l __attribute__((__mode__(__SI__))); float __d; }) \ 40 { __l: 0x7fbfffffUL }).__d) 41 42 #else 43 44 # include <endian.h> 45 46 # if __BYTE_ORDER == __BIG_ENDIAN 47 # define __nan_bytes { 0x7f, 0xbf, 0xff, 0xff } 48 # endif 49 # if __BYTE_ORDER == __LITTLE_ENDIAN 50 # define __nan_bytes { 0xff, 0xff, 0xbf, 0x7f } 51 # endif 52 53 static union { unsigned char __c[4]; float __d; } __nan_union = { __nan_bytes }; 54 # define NAN (__nan_union.__d) 55 56 #endif /* GCC. */ 57