nan.h 1.6 KB

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  1. /* `NAN' constant for IEEE 754 machines.
  2. Copyright (C) 1992, 1996, 1997, 1999 Free Software Foundation, Inc.
  3. This file is part of the GNU C Library.
  4. The GNU C Library is free software; you can redistribute it and/or
  5. modify it under the terms of the GNU Library General Public License as
  6. published by the Free Software Foundation; either version 2 of the
  7. License, or (at your option) any later version.
  8. The GNU C Library is distributed in the hope that it will be useful,
  9. but WITHOUT ANY WARRANTY; without even the implied warranty of
  10. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  11. Library General Public License for more details.
  12. You should have received a copy of the GNU Library General Public
  13. License along with the GNU C Library; see the file COPYING.LIB. If not,
  14. write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  15. Boston, MA 02111-1307, USA. */
  16. #ifndef _MATH_H
  17. # error "Never use <bits/nan.h> directly; include <math.h> instead."
  18. #endif
  19. /* IEEE Not A Number. */
  20. #ifdef __GNUC__
  21. # define NAN \
  22. (__extension__ \
  23. ((union { unsigned __l __attribute__((__mode__(__SI__))); float __d; }) \
  24. { __l: 0x7fc00000UL }).__d)
  25. #else
  26. # include <endian.h>
  27. # if __BYTE_ORDER == __BIG_ENDIAN
  28. # define __nan_bytes { 0x7f, 0xc0, 0, 0 }
  29. # endif
  30. # if __BYTE_ORDER == __LITTLE_ENDIAN
  31. # define __nan_bytes { 0, 0, 0xc0, 0x7f }
  32. # endif
  33. static union { unsigned char __c[4]; float __d; } __nan_union = { __nan_bytes };
  34. # define NAN (__nan_union.__d)
  35. #endif /* GCC. */