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tasks/libposix/include/posix/bits/nan.h

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+/* `NAN' constant for IEEE 754 machines.
+   Copyright (C) 1992,1996,1997,1999,2004,2006 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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#ifndef _MATH_H
+# error "Never use <bits/nan.h> directly; include <math.h> instead."
+#endif
+
+
+/* IEEE Not A Number.  */
+
+#if __GNUC_PREREQ(3,3)
+
+# define NAN	(__builtin_nanf (""))
+
+#elif defined __GNUC__
+
+# define NAN \
+  (__extension__							      \
+   ((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; })  \
+    { __l: 0x7fc00000UL }).__d)
+
+#else
+
+# include <endian.h>
+
+# if __BYTE_ORDER == __BIG_ENDIAN
+#  define __nan_bytes		{ 0x7f, 0xc0, 0, 0 }
+# endif
+# if __BYTE_ORDER == __LITTLE_ENDIAN
+#  define __nan_bytes		{ 0, 0, 0xc0, 0x7f }
+# endif
+
+static union { unsigned char __c[4]; float __d; } __nan_union
+    __attribute_used__ = { __nan_bytes };
+# define NAN	(__nan_union.__d)
+
+#endif	/* GCC.  */