sysdeps/ieee754/nan.h

   1 /* `NAN' constant for IEEE 754 machines.
   2    Copyright (C) 1992, 1996 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 Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    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    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #ifndef _NAN_H
  21
  22 #define _NAN_H  1
  23
  24 /* IEEE Not A Number.  */
  25
  26 #include <endian.h>
  27
  28 #if __BYTE_ORDER == __BIG_ENDIAN
  29 #define __nan_bytes             { 0x7f, 0xf8, 0, 0, 0, 0, 0, 0 }
  30 #endif
  31 #if __BYTE_ORDER == __LITTLE_ENDIAN
  32 #define __nan_bytes             { 0, 0, 0, 0, 0, 0, 0xf8, 0x7f }
  33 #endif
  34
  35 #ifdef  __GNUC__
  36 #define NAN \
  37   (__extension__ ((union { unsigned char __c[8];                              \
  38                            double __d; })                                     \
  39                   { __nan_bytes }).__d)
  40 #else   /* Not GCC.  */
  41 static CONST char __nan[8] = __nan_bytes;
  42 #define NAN     (*(CONST double *) __nan)
  43 #endif  /* GCC.  */
  44
  45 #endif  /* nan.h */