huge_vall.h

glibc 2.9,最新版的C语言库函数

/* `HUGE_VALL' constant for IEEE 754 machines (where it is infinity).
   Used by <stdlib.h> and <math.h> functions for overflow.
   Copyright (C) 1992, 1995, 1996, 1997, 1999, 2000, 2004
   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, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

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

#if __GNUC_PREREQ(3,3)
# define HUGE_VALL	(__builtin_huge_vall())
#else
# include <bits/wordsize.h>
# if __WORDSIZE == 32
#  define HUGE_VALL	((long double) HUGE_VAL)
# elif __GNUC_PREREQ(2,96)
#   define HUGE_VALL	(__extension__ 0x1.0p32767L)
# elif defined __GNUC__

#   define HUGE_VALL \
  (__extension__							 \
   ((union { struct { unsigned long __h, __l; } __i; long double __d; }) \
    { __i: { __h: 0x7fff000000000000UL, __l: 0 } }).__d)

# else /* not GCC */

typedef union { unsigned char __c[16]; long double __d; } __huge_vall_t;
#  define __HUGE_VALL_bytes	{ 0x7f, 0xff, 0,0,0,0,0,0,0,0,0,0,0,0,0,0 }
static __huge_vall_t __huge_vall = { __HUGE_VALL_bytes };
#  define HUGE_VALL	(__huge_vall.__d)

# endif /* GCC.  */
#endif /* GCC 3.3.  */