1 /* Copyright (C) 2001-2003, 2006-2021 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 3, 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, see <https://www.gnu.org/licenses/>. */
16
17 #ifndef _GL_STDBOOL_H
18 #define _GL_STDBOOL_H
19
20 /* ISO C 99 <stdbool.h> for platforms that lack it. */
21
22 /* Usage suggestions:
23
24 Programs that use <stdbool.h> should be aware of some limitations
25 and standards compliance issues.
26
27 Standards compliance:
28
29 - <stdbool.h> must be #included before 'bool', 'false', 'true'
30 can be used.
31
32 - You cannot assume that sizeof (bool) == 1.
33
34 - Programs should not undefine the macros bool, true, and false,
35 as C99 lists that as an "obsolescent feature".
36
37 Limitations of this substitute, when used in a C89 environment:
38
39 - <stdbool.h> must be #included before the '_Bool' type can be used.
40
41 - You cannot assume that _Bool is a typedef; it might be a macro.
42
43 - Bit-fields of type 'bool' are not supported. Portable code
44 should use 'unsigned int foo : 1;' rather than 'bool foo : 1;'.
45
46 - In C99, casts and automatic conversions to '_Bool' or 'bool' are
47 performed in such a way that every nonzero value gets converted
48 to 'true', and zero gets converted to 'false'. This doesn't work
49 with this substitute. With this substitute, only the values 0 and 1
50 give the expected result when converted to _Bool' or 'bool'.
51
52 - C99 allows the use of (_Bool)0.0 in constant expressions, but
53 this substitute cannot always provide this property.
54
55 Also, it is suggested that programs use 'bool' rather than '_Bool';
56 this isn't required, but 'bool' is more common. */
57
58
59 /* 7.16. Boolean type and values */
60
61 /* BeOS <sys/socket.h> already #defines false 0, true 1. We use the same
62 definitions below, but temporarily we have to #undef them. */
63 #if defined __BEOS__ && !defined __HAIKU__
64 # include <OS.h> /* defines bool but not _Bool */
65 # undef false
66 # undef true
67 #endif
68
69 #ifdef __cplusplus
70 # define _Bool bool
71 # define bool bool
72 #else
73 # if defined __BEOS__ && !defined __HAIKU__
74 /* A compiler known to have 'bool'. */
75 /* If the compiler already has both 'bool' and '_Bool', we can assume they
76 are the same types. */
77 # if !@HAVE__BOOL@
78 typedef bool _Bool;
79 # endif
80 # else
81 # if !defined __GNUC__
82 /* If @HAVE__BOOL@:
83 Some HP-UX cc and AIX IBM C compiler versions have compiler bugs when
84 the built-in _Bool type is used. See
85 https://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
86 https://lists.gnu.org/r/bug-coreutils/2005-11/msg00161.html
87 https://lists.gnu.org/r/bug-coreutils/2005-10/msg00086.html
88 Similar bugs are likely with other compilers as well; this file
89 wouldn't be used if <stdbool.h> was working.
90 So we override the _Bool type.
91 If !@HAVE__BOOL@:
92 Need to define _Bool ourselves. As 'signed char' or as an enum type?
93 Use of a typedef, with SunPRO C, leads to a stupid
94 "warning: _Bool is a keyword in ISO C99".
95 Use of an enum type, with IRIX cc, leads to a stupid
96 "warning(1185): enumerated type mixed with another type".
97 Even the existence of an enum type, without a typedef,
98 "Invalid enumerator. (badenum)" with HP-UX cc on Tru64.
99 The only benefit of the enum, debuggability, is not important
100 with these compilers. So use 'signed char' and no enum. */
101 # define _Bool signed char
102 # else
103 /* With this compiler, trust the _Bool type if the compiler has it. */
104 # if !@HAVE__BOOL@
105 /* For the sake of symbolic names in gdb, define true and false as
106 enum constants, not only as macros.
107 It is tempting to write
108 typedef enum { false = 0, true = 1 } _Bool;
109 so that gdb prints values of type 'bool' symbolically. But then
110 values of type '_Bool' might promote to 'int' or 'unsigned int'
111 (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
112 (see ISO C 99 6.3.1.1.(2)). So add a negative value to the
113 enum; this ensures that '_Bool' promotes to 'int'. */
114 typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
115 # endif
116 # endif
117 # endif
118 # define bool _Bool
119 #endif
120
121 /* The other macros must be usable in preprocessor directives. */
122 #ifdef __cplusplus
123 # define false false
124 # define true true
125 #else
126 # define false 0
127 # define true 1
128 #endif
129
130 #define __bool_true_false_are_defined 1
131
132 #endif /* _GL_STDBOOL_H */