glibc/bits/wchar.h

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/* wchar_t type related definitions.
Copyright (C) 2000-2015 Free Software Foundation, Inc.
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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.
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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.
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You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
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#ifndef _BITS_WCHAR_H
#define _BITS_WCHAR_H 1
/* The fallback definitions, for when __WCHAR_MAX__ or __WCHAR_MIN__
are not defined, give the right value and type as long as both int
and wchar_t are 32-bit types. Adding L'\0' to a constant value
ensures that the type is correct; it is necessary to use (L'\0' +
0) rather than just L'\0' so that the type in C++ is the promoted
version of wchar_t rather than the distinct wchar_t type itself.
Because wchar_t in preprocessor #if expressions is treated as
intmax_t or uintmax_t, the expression (L'\0' - 1) would have the
wrong value for WCHAR_MAX in such expressions and so cannot be used
to define __WCHAR_MAX in the unsigned case. */
#ifdef __WCHAR_MAX__
# define __WCHAR_MAX __WCHAR_MAX__
#elif L'\0' - 1 > 0
# define __WCHAR_MAX (0xffffffffu + L'\0')
#else
# define __WCHAR_MAX (0x7fffffff + L'\0')
#endif
#ifdef __WCHAR_MIN__
# define __WCHAR_MIN __WCHAR_MIN__
#elif L'\0' - 1 > 0
# define __WCHAR_MIN (L'\0' + 0)
#else
# define __WCHAR_MIN (-__WCHAR_MAX - 1)
#endif
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#endif /* bits/wchar.h */