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53 lines
1.5 KiB
C
53 lines
1.5 KiB
C
/* `NAN' constant for IEEE 754 machines.
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Copyright (C) 1992-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _MATH_H
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# error "Never use <bits/nan.h> directly; include <math.h> instead."
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#endif
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/* IEEE Not A Number. */
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#if __GNUC_PREREQ(3,3)
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# define NAN (__builtin_nanf (""))
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#elif defined __GNUC__
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# define NAN \
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(__extension__ \
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((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; }) \
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{ __l: 0x7fc00000UL }).__d)
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#else
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# include <endian.h>
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# if __BYTE_ORDER == __BIG_ENDIAN
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# define __qnan_bytes { 0x7f, 0xc0, 0, 0 }
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# endif
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# if __BYTE_ORDER == __LITTLE_ENDIAN
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# define __qnan_bytes { 0, 0, 0xc0, 0x7f }
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# endif
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static union { unsigned char __c[4]; float __d; } __qnan_union
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__attribute__ ((__unused__)) = { __qnan_bytes };
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# define NAN (__qnan_union.__d)
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#endif /* GCC. */
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