glibc/ports/sysdeps/mips/bits/nan.h

/* `NAN' constant for IEEE 754 machines.  MIPS version.
   Copyright (C) 1992-2013 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#ifndef _MATH_H
# error "Never use <bits/nan.h> directly; include <math.h> instead."
#endif


/* IEEE Not A Number.  */
/* Note that MIPS has the QNaN and SNaN patterns reversed compared to most
   other architectures.  The IEEE spec left the definition of this open to
   implementations, and for MIPS the top bit of the mantissa must be SET to
   indicate a SNaN.  */

#if __GNUC_PREREQ(3,3)

# define NAN	(__builtin_nanf (""))

#elif defined __GNUC__

# define NAN \
  (__extension__							      \
   ((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; })  \
    { __l: 0x7fbfffffUL }).__d)

#else

# include <endian.h>

# if __BYTE_ORDER == __BIG_ENDIAN
#  define __nan_bytes		{ 0x7f, 0xbf, 0xff, 0xff }
# endif
# if __BYTE_ORDER == __LITTLE_ENDIAN
#  define __nan_bytes		{ 0xff, 0xff, 0xbf, 0x7f }
# endif

static union { unsigned char __c[4]; float __d; } __nan_union
  __attribute__ ((__unused__)) = { __nan_bytes };
# define NAN	(__nan_union.__d)

#endif	/* GCC.  */