1/* Copyright (C) 2001-2003, 2006-2010 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 Lesser 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 Lesser General Public License for more details.
13
14   You should have received a copy of the GNU Lesser 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       - C99 allows the use of (_Bool)0.0 in constant expressions, but
54         this substitute cannot always provide this property.
55
56   Also, it is suggested that programs use 'bool' rather than '_Bool';
57   this isn't required, but 'bool' is more common.  */
58
59
60/* 7.16. Boolean type and values */
61
62/* BeOS <sys/socket.h> already #defines false 0, true 1.  We use the same
63   definitions below, but temporarily we have to #undef them.  */
64#if defined __BEOS__ && !defined __HAIKU__
65# include <OS.h> /* defines bool but not _Bool */
66# undef false
67# undef true
68#endif
69
70/* For the sake of symbolic names in gdb, we define true and false as
71   enum constants, not only as macros.
72   It is tempting to write
73      typedef enum { false = 0, true = 1 } _Bool;
74   so that gdb prints values of type 'bool' symbolically. But if we do
75   this, values of type '_Bool' may promote to 'int' or 'unsigned int'
76   (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
77   (see ISO C 99 6.3.1.1.(2)).  So we add a negative value to the
78   enum; this ensures that '_Bool' promotes to 'int'.  */
79#if defined __cplusplus || (defined __BEOS__ && !defined __HAIKU__)
80  /* A compiler known to have 'bool'.  */
81  /* If the compiler already has both 'bool' and '_Bool', we can assume they
82     are the same types.  */
83# if !@HAVE__BOOL@
84typedef bool _Bool;
85# endif
86#else
87# if !defined __GNUC__
88   /* If @HAVE__BOOL@:
89        Some HP-UX cc and AIX IBM C compiler versions have compiler bugs when
90        the built-in _Bool type is used.  See
91          http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
92          http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
93          http://lists.gnu.org/archive/html/bug-coreutils/2005-10/msg00086.html
94        Similar bugs are likely with other compilers as well; this file
95        wouldn't be used if <stdbool.h> was working.
96        So we override the _Bool type.
97      If !@HAVE__BOOL@:
98        Need to define _Bool ourselves. As 'signed char' or as an enum type?
99        Use of a typedef, with SunPRO C, leads to a stupid
100          "warning: _Bool is a keyword in ISO C99".
101        Use of an enum type, with IRIX cc, leads to a stupid
102          "warning(1185): enumerated type mixed with another type".
103        Even the existence of an enum type, without a typedef,
104          "Invalid enumerator. (badenum)" with HP-UX cc on Tru64.
105        The only benefit of the enum, debuggability, is not important
106        with these compilers.  So use 'signed char' and no enum.  */
107#  define _Bool signed char
108# else
109   /* With this compiler, trust the _Bool type if the compiler has it.  */
110#  if !@HAVE__BOOL@
111typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
112#  endif
113# endif
114#endif
115#define bool _Bool
116
117/* The other macros must be usable in preprocessor directives.  */
118#define false 0
119#define true 1
120#define __bool_true_false_are_defined 1
121
122#endif /* _GL_STDBOOL_H */
123