sysdeps/ieee754/nan.h

   1 /* `NAN' constant for IEEE 754 machines.
   2
   3 Copyright (C) 1992 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 Library General Public License as
   8 published by the Free Software Foundation; either version 2 of the
   9 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 Library General Public License for more details.
  15
  16 You should have received a copy of the GNU Library General Public
  17 License along with the GNU C Library; see the file COPYING.LIB.  If
  18 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  19 Cambridge, MA 02139, USA.  */
  20
  21 #ifndef _NAN_H
  22
  23 #define _NAN_H  1
  24
  25 /* IEEE Not A Number.  */
  26
  27 #include <endian.h>
  28
  29 #if __BYTE_ORDER == __BIG_ENDIAN
  30 #define __nan_bytes             { 0x7f, 0xf8, 0, 0, 0, 0, 0, 0 }
  31 #endif
  32 #if __BYTE_ORDER == __LITTLE_ENDIAN
  33 #define __nan_bytes             { 0, 0, 0, 0, 0, 0, 0xf8, 0x7f }
  34 #endif
  35
  36 #ifdef  __GNUC__
  37 #define NAN \
  38   (__extension__ ((union { unsigned char __c[8];                              \
  39                            double __d; })                                     \
  40                   { __nan_bytes }).__d)
  41 #else   /* Not GCC.  */
  42 static CONST char __nan[8] = __nan_bytes;
  43 #define NAN     (*(CONST double *) __nan)
  44 #endif  /* GCC.  */
  45
  46 #endif  /* nan.h */