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1 /* Copyright (C) 2001, 2002, 2003, 2006 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 _STDBOOL_H
19 #define _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        - In C99, casts and automatic conversions to '_Bool' or 'bool' are
45          performed in such a way that every nonzero value gets converted
46          to 'true', and zero gets converted to 'false'.  This doesn't work
47          with this substitute.  With this substitute, only the values 0 and 1
48          give the expected result when converted to _Bool' or 'bool'.
49 
50    Also, it is suggested that programs use 'bool' rather than '_Bool';
51    this isn't required, but 'bool' is more common.  */
52 
53 
54 /* 7.16. Boolean type and values */
55 
56 /* BeOS <sys/socket.h> already #defines false 0, true 1.  We use the same
57    definitions below, but temporarily we have to #undef them.  */
58 #ifdef __BEOS__
59 # include <OS.h> /* defines bool but not _Bool */
60 # undef false
61 # undef true
62 #endif
63 
64 /* For the sake of symbolic names in gdb, we define true and false as
65    enum constants, not only as macros.
66    It is tempting to write
67       typedef enum { false = 0, true = 1 } _Bool;
68    so that gdb prints values of type 'bool' symbolically. But if we do
69    this, values of type '_Bool' may promote to 'int' or 'unsigned int'
70    (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
71    (see ISO C 99 6.3.1.1.(2)).  So we add a negative value to the
72    enum; this ensures that '_Bool' promotes to 'int'.  */
73 #if defined __cplusplus || defined __BEOS__
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           http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
86           http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
87           http://lists.gnu.org/archive/html/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         The only benefit of the enum type, debuggability, is not important
98         with these compilers.  So use 'signed char' and no typedef.  */
99 #  define _Bool signed char
100 enum { false = 0, true = 1 };
101 # else
102    /* With this compiler, trust the _Bool type if the compiler has it.  */
103 #  if !@HAVE__BOOL@
104 typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
105 #  endif
106 # endif
107 #endif
108 #define bool _Bool
109 
110 /* The other macros must be usable in preprocessor directives.  */
111 #define false 0
112 #define true 1
113 #define __bool_true_false_are_defined 1
114 
115 #endif /* _STDBOOL_H */
116