huge_val.h

它通过提供glibc兼容使得应用程序移植到较小的c 库时相当得容易. 它能够应用到带虚拟存储的Linux和uClinux上.在大多数带MMU部件的平台上为使它更加紧凑,它也能够编译成共享库.uClib

/* `HUGE_VAL' constants for m68k (where it is infinity).
   Used by <stdlib.h> and <math.h> functions for overflow.
   Copyright (C) 1992, 1995, 1996, 1997 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 Library General Public License as
   published by the Free Software Foundation; either version 2 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  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_val.h> directly; include <math.h> instead."
#endif


#include <features.h>
#include <sys/cdefs.h>

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

#ifdef	__GNUC__

# define HUGE_VAL					\
  (__extension__					\
   ((union { unsigned long long __l; double __d; })	\
    { __l: 0x7ff0000000000000ULL }).__d)

#else /* not GCC */

static union { unsigned char __c[8]; double __d; } __huge_val =
  { { 0x7f, 0xf0, 0, 0, 0, 0, 0, 0 } };
# define HUGE_VAL	(__huge_val.__d)

#endif	/* GCC.  */


/* ISO C 9X extensions: (float) HUGE_VALF and (long double) HUGE_VALL.  */

#ifdef __USE_ISOC9X

# ifdef __GNUC__

#  define HUGE_VALF					\
  (__extension__					\
   ((union { unsigned long __l; float __f; })		\
    { __l: 0x7f800000UL }).__f)

#  define HUGE_VALL					\
  (__extension__					\
   ((union { unsigned long __l[3]; long double __ld; })	\
    { __l: { 0x7fff0000UL, 0x80000000UL, 0UL } }).__ld)

# else /* not GCC */

static union { unsigned char __c[4]; float __f; } __huge_valf =
  { { 0x7f, 0x80, 0, 0 } };
#  define HUGE_VALF	(__huge_valf.__f)

static union { unsigned char __c[12]; long double __ld; } __huge_vall =
  { { 0x7f, 0xff, 0, 0, 0x80, 0, 0, 0, 0, 0, 0, 0 } };
#  define HUGE_VALL	(__huge_vall.__ld)

# endif	/* GCC.  */

#endif	/* __USE_ISOC9X.  */