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glibc  2.9
huge_vall.h
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00001 /* `HUGE_VALL' 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_vall.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_VALL   (__builtin_huge_vall())
00030 #elif __GNUC_PREREQ(2,96)
00031 # define HUGE_VALL   (__extension__ 0x1.0p32767L)
00032 #else
00033 # include <endian.h>
00034 
00035 typedef union { unsigned char __c[16]; long double __ld; } __huge_vall_t;
00036 
00037 # if __BYTE_ORDER == __BIG_ENDIAN
00038 #  define __HUGE_VALL_bytes { 0x7f, 0xff, 0,0,0,0,0,0,0,0,0,0,0,0,0,0 }
00039 # endif
00040 # if __BYTE_ORDER == __LITTLE_ENDIAN
00041 #  define __HUGE_VALL_bytes { 0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0xff, 0x7f }
00042 # endif
00043 
00044 # ifdef __GNUC__
00045 #  define HUGE_VALL  (__extension__ \
00046                       ((__huge_vall_t) { __c : __HUGE_VALL_bytes }).__ld)
00047 # else
00048 static __huge_vall_t __huge_vall = { __HUGE_VALL_bytes };
00049 #  define HUGE_VALL  (__huge_vall.__ld)
00050 # endif
00051 #endif