✏ 编辑: huge_valf.h

/* `HUGE_VALF' 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, see
   <http://www.gnu.org/licenses/>.  */

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

/* IEEE positive infinity (-HUGE_VAL is negative infinity).  */

#if __GNUC_PREREQ(3,3)
# define HUGE_VALF	(__builtin_huge_valf())
#elif __GNUC_PREREQ(2,96)
# define HUGE_VALF	(__extension__ 0x1.0p255f)
#elif defined __GNUC__

#   define HUGE_VALF \
  (__extension__							      \
   ((union { unsigned __l __attribute__((__mode__(__SI__))); float __d; })    \
    { __l: 0x7f800000UL }).__d)

#else /* not GCC */

typedef union { unsigned char __c[4]; float __f; } __huge_valf_t;

# if __BYTE_ORDER == __BIG_ENDIAN
#  define __HUGE_VALF_bytes	{ 0x7f, 0x80, 0, 0 }
# endif
# if __BYTE_ORDER == __LITTLE_ENDIAN
#  define __HUGE_VALF_bytes	{ 0, 0, 0x80, 0x7f }
# endif

static __huge_valf_t __huge_valf = { __HUGE_VALF_bytes };
# define HUGE_VALF	(__huge_valf.__f)

#endif	/* GCC.  */

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