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94 lines
3.4 KiB
C
94 lines
3.4 KiB
C
/* Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
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Written by Bruno Haible <haible@clisp.cons.org>, 2001.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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#ifndef _STDBOOL_H
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#define _STDBOOL_H
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/* ISO C 99 <stdbool.h> for platforms that lack it. */
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/* Usage suggestions:
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Programs that use <stdbool.h> should be aware of some limitations
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and standards compliance issues.
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Standards compliance:
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- <stdbool.h> must be #included before 'bool', 'false', 'true'
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can be used.
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- You cannot assume that sizeof (bool) == 1.
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- Programs should not undefine the macros bool, true, and false,
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as C99 lists that as an "obsolescent feature".
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Limitations of this substitute, when used in a C89 environment:
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- <stdbool.h> must be #included before the '_Bool' type can be used.
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- You cannot assume that _Bool is a typedef; it might be a macro.
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- In C99, casts and automatic conversions to '_Bool' or 'bool' are
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performed in such a way that every nonzero value gets converted
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to 'true', and zero gets converted to 'false'. This doesn't work
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with this substitute. With this substitute, only the values 0 and 1
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give the expected result when converted to _Bool' or 'bool'.
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Also, it is suggested that programs use 'bool' rather than '_Bool';
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this isn't required, but 'bool' is more common. */
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/* 7.16. Boolean type and values */
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/* BeOS <sys/socket.h> already #defines false 0, true 1. We use the same
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definitions below, but temporarily we have to #undef them. */
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#ifdef __BEOS__
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# include <OS.h> /* defines bool but not _Bool */
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# undef false
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# undef true
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#endif
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/* For the sake of symbolic names in gdb, we define true and false as
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enum constants, not only as macros.
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It is tempting to write
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typedef enum { false = 0, true = 1 } _Bool;
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so that gdb prints values of type 'bool' symbolically. But if we do
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this, values of type '_Bool' may promote to 'int' or 'unsigned int'
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(see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
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(see ISO C 99 6.3.1.1.(2)). So we add a negative value to the
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enum; this ensures that '_Bool' promotes to 'int'. */
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#if !(defined __cplusplus || defined __BEOS__)
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# if !@HAVE__BOOL@
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# if defined __SUNPRO_C && (__SUNPRO_C < 0x550 || __STDC__ == 1)
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/* Avoid stupid "warning: _Bool is a keyword in ISO C99". */
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# define _Bool signed char
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enum { false = 0, true = 1 };
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# else
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typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
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# endif
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# endif
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#else
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typedef bool _Bool;
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#endif
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#define bool _Bool
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/* The other macros must be usable in preprocessor directives. */
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#define false 0
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#define true 1
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#define __bool_true_false_are_defined 1
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#endif /* _STDBOOL_H */
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