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comparison lib/stdbool.in.h @ 265:68fbca173508 2.6

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date Tue, 22 Dec 2009 05:31:23 +0000
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264:61d1db1dfe2a 265:68fbca173508
1 /* Copyright (C) 2001-2003, 2006-2008 Free Software Foundation, Inc.
2 Written by Bruno Haible <haible@clisp.cons.org>, 2001.
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
7 any later version.
8
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
13
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software Foundation,
16 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
17
18 #ifndef _GL_STDBOOL_H
19 #define _GL_STDBOOL_H
20
21 /* ISO C 99 <stdbool.h> for platforms that lack it. */
22
23 /* Usage suggestions:
24
25 Programs that use <stdbool.h> should be aware of some limitations
26 and standards compliance issues.
27
28 Standards compliance:
29
30 - <stdbool.h> must be #included before 'bool', 'false', 'true'
31 can be used.
32
33 - You cannot assume that sizeof (bool) == 1.
34
35 - Programs should not undefine the macros bool, true, and false,
36 as C99 lists that as an "obsolescent feature".
37
38 Limitations of this substitute, when used in a C89 environment:
39
40 - <stdbool.h> must be #included before the '_Bool' type can be used.
41
42 - You cannot assume that _Bool is a typedef; it might be a macro.
43
44 - Bit-fields of type 'bool' are not supported. Portable code
45 should use 'unsigned int foo : 1;' rather than 'bool foo : 1;'.
46
47 - In C99, casts and automatic conversions to '_Bool' or 'bool' are
48 performed in such a way that every nonzero value gets converted
49 to 'true', and zero gets converted to 'false'. This doesn't work
50 with this substitute. With this substitute, only the values 0 and 1
51 give the expected result when converted to _Bool' or 'bool'.
52
53 Also, it is suggested that programs use 'bool' rather than '_Bool';
54 this isn't required, but 'bool' is more common. */
55
56
57 /* 7.16. Boolean type and values */
58
59 /* BeOS <sys/socket.h> already #defines false 0, true 1. We use the same
60 definitions below, but temporarily we have to #undef them. */
61 #if defined __BEOS__ && !defined __HAIKU__
62 # include <OS.h> /* defines bool but not _Bool */
63 # undef false
64 # undef true
65 #endif
66
67 /* For the sake of symbolic names in gdb, we define true and false as
68 enum constants, not only as macros.
69 It is tempting to write
70 typedef enum { false = 0, true = 1 } _Bool;
71 so that gdb prints values of type 'bool' symbolically. But if we do
72 this, values of type '_Bool' may promote to 'int' or 'unsigned int'
73 (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
74 (see ISO C 99 6.3.1.1.(2)). So we add a negative value to the
75 enum; this ensures that '_Bool' promotes to 'int'. */
76 #if defined __cplusplus || (defined __BEOS__ && !defined __HAIKU__)
77 /* A compiler known to have 'bool'. */
78 /* If the compiler already has both 'bool' and '_Bool', we can assume they
79 are the same types. */
80 # if !@HAVE__BOOL@
81 typedef bool _Bool;
82 # endif
83 #else
84 # if !defined __GNUC__
85 /* If @HAVE__BOOL@:
86 Some HP-UX cc and AIX IBM C compiler versions have compiler bugs when
87 the built-in _Bool type is used. See
88 http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
89 http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
90 http://lists.gnu.org/archive/html/bug-coreutils/2005-10/msg00086.html
91 Similar bugs are likely with other compilers as well; this file
92 wouldn't be used if <stdbool.h> was working.
93 So we override the _Bool type.
94 If !@HAVE__BOOL@:
95 Need to define _Bool ourselves. As 'signed char' or as an enum type?
96 Use of a typedef, with SunPRO C, leads to a stupid
97 "warning: _Bool is a keyword in ISO C99".
98 Use of an enum type, with IRIX cc, leads to a stupid
99 "warning(1185): enumerated type mixed with another type".
100 Even the existence of an enum type, without a typedef,
101 "Invalid enumerator. (badenum)" with HP-UX cc on Tru64.
102 The only benefit of the enum, debuggability, is not important
103 with these compilers. So use 'signed char' and no enum. */
104 # define _Bool signed char
105 # else
106 /* With this compiler, trust the _Bool type if the compiler has it. */
107 # if !@HAVE__BOOL@
108 typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
109 # endif
110 # endif
111 #endif
112 #define bool _Bool
113
114 /* The other macros must be usable in preprocessor directives. */
115 #define false 0
116 #define true 1
117 #define __bool_true_false_are_defined 1
118
119 #endif /* _GL_STDBOOL_H */