glibc/bits/wchar.h

/* wchar_t type related definitions.
   Copyright (C) 2000-2017 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, see
   <http://www.gnu.org/licenses/>.  */

#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

#endif	/* bits/wchar.h */