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glibc  2.9
huge_val.h
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00001 /* `HUGE_VAL' constant for IEEE 754 machines (where it is infinity).
00002    Used by <stdlib.h> and <math.h> functions for overflow.
00003    Copyright (C) 1992, 1995, 1996, 1997, 1999, 2000, 2004
00004    Free Software Foundation, Inc.
00005    This file is part of the GNU C Library.
00006 
00007    The GNU C Library is free software; you can redistribute it and/or
00008    modify it under the terms of the GNU Lesser General Public
00009    License as published by the Free Software Foundation; either
00010    version 2.1 of the License, or (at your option) any later version.
00011 
00012    The GNU C Library is distributed in the hope that it will be useful,
00013    but WITHOUT ANY WARRANTY; without even the implied warranty of
00014    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015    Lesser General Public License for more details.
00016 
00017    You should have received a copy of the GNU Lesser General Public
00018    License along with the GNU C Library; if not, write to the Free
00019    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00020    02111-1307 USA.  */
00021 
00022 #ifndef _MATH_H
00023 # error "Never use <bits/huge_val.h> directly; include <math.h> instead."
00024 #endif
00025 
00026 /* IEEE positive infinity (-HUGE_VAL is negative infinity).  */
00027 
00028 #if __GNUC_PREREQ(3,3)
00029 # define HUGE_VAL    (__builtin_huge_val())
00030 #elif __GNUC_PREREQ(2,96)
00031 # define HUGE_VAL    (__extension__ 0x1.0p2047)
00032 #elif defined __GNUC__
00033 
00034 # define HUGE_VAL \
00035   (__extension__                                                     \
00036    ((union { unsigned __l __attribute__((__mode__(__DI__))); double __d; })   \
00037     { __l: 0x7ff0000000000000ULL }).__d)
00038 
00039 #else /* not GCC */
00040 
00041 # include <endian.h>
00042 
00043 typedef union { unsigned char __c[8]; double __d; } __huge_val_t;
00044 
00045 # if __BYTE_ORDER == __BIG_ENDIAN
00046 #  define __HUGE_VAL_bytes  { 0x7f, 0xf0, 0, 0, 0, 0, 0, 0 }
00047 # endif
00048 # if __BYTE_ORDER == __LITTLE_ENDIAN
00049 #  define __HUGE_VAL_bytes  { 0, 0, 0, 0, 0, 0, 0xf0, 0x7f }
00050 # endif
00051 
00052 static __huge_val_t __huge_val = { __HUGE_VAL_bytes };
00053 # define HUGE_VAL    (__huge_val.__d)
00054 
00055 #endif /* GCC.  */