1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
|
/* Copyright (C) 2001, 2002, 2003, 2005 Free Software Foundation, Inc.
Written by Bruno Haible <haible@clisp.cons.org>, 2001.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
#ifndef _STDBOOL_H
#define _STDBOOL_H
/* ISO C 99 <stdbool.h> for platforms that lack it. */
/* Usage suggestions:
Programs that use <stdbool.h> should be aware of some limitations
and standards compliance issues.
Standards compliance:
- <stdbool.h> must be #included before 'bool', 'false', 'true'
can be used.
- You cannot assume that sizeof (bool) == 1.
- Programs should not undefine the macros bool, true, and false,
as C99 lists that as an "obsolescent feature".
Limitations of this substitute, when used in a C89 environment:
- <stdbool.h> must be #included before the '_Bool' type can be used.
- You cannot assume that _Bool is a typedef; it might be a macro.
- In C99, casts and automatic conversions to '_Bool' or 'bool' are
performed in such a way that every nonzero value gets converted
to 'true', and zero gets converted to 'false'. This doesn't work
with this substitute. With this substitute, only the values 0 and 1
give the expected result when converted to _Bool' or 'bool'.
Also, it is suggested that programs use 'bool' rather than '_Bool';
this isn't required, but 'bool' is more common. */
/* 7.16. Boolean type and values */
/* BeOS <sys/socket.h> already #defines false 0, true 1. We use the same
definitions below, which is OK. */
#ifdef __BEOS__
# include <OS.h> /* defines bool but not _Bool */
#endif
/* C++ and BeOS have a reliable _Bool. Otherwise, since this file is
being compiled, the system <stdbool.h> is not reliable so assume
that the system _Bool is not reliable either. Under that
assumption, it is tempting to write
typedef enum { false, true } _Bool;
so that gdb prints values of type 'bool' symbolically. But if we do
this, values of type '_Bool' may promote to 'int' or 'unsigned int'
(see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
(see ISO C 99 6.3.1.1.(2)). We could instead try this:
typedef enum { _Bool_dummy = -1, false, true } _Bool;
as the negative value ensures that '_Bool' promotes to 'int'.
However, this runs into some other problems. First, Sun's C
compiler when (__SUNPRO_C < 0x550 || __STDC__ == 1) issues a stupid
"warning: _Bool is a keyword in ISO C99". Second, IBM's AIX cc
compiler 6.0.0.0 (and presumably other versions) mishandles
subscripts involving _Bool (effectively, _Bool promotes to unsigned
int in this case), and we need to redefine _Bool in that case.
Third, HP-UX 10.20's C compiler lacks <stdbool.h> but has _Bool and
mishandles comparisons of _Bool to int (it promotes _Bool to
unsigned int).
The simplest way to work around these problems is to ignore any
existing definition of _Bool and use our own. */
#if defined __cplusplus || defined __BEOS__
typedef bool _Bool;
#else
# define _Bool signed char
#endif
#define bool _Bool
/* The other macros must be usable in preprocessor directives. */
#define false 0
#define true 1
#define __bool_true_false_are_defined 1
#endif /* _STDBOOL_H */
|
