Silence various byte-compiler warnings.
[emacs.git] / lib / stdbool.in.h
blobb64dc75b20cc57836e4fdc8e6e2cd5f6e316c5f9
1 /* Copyright (C) 2001-2003, 2006-2011 Free Software Foundation, Inc.
2 Written by Bruno Haible <haible@clisp.cons.org>, 2001.
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.
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.
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. */
18 #ifndef _GL_STDBOOL_H
19 #define _GL_STDBOOL_H
21 /* ISO C 99 <stdbool.h> for platforms that lack it. */
23 /* Usage suggestions:
25 Programs that use <stdbool.h> should be aware of some limitations
26 and standards compliance issues.
28 Standards compliance:
30 - <stdbool.h> must be #included before 'bool', 'false', 'true'
31 can be used.
33 - You cannot assume that sizeof (bool) == 1.
35 - Programs should not undefine the macros bool, true, and false,
36 as C99 lists that as an "obsolescent feature".
38 Limitations of this substitute, when used in a C89 environment:
40 - <stdbool.h> must be #included before the '_Bool' type can be used.
42 - You cannot assume that _Bool is a typedef; it might be a macro.
44 - Bit-fields of type 'bool' are not supported. Portable code
45 should use 'unsigned int foo : 1;' rather than 'bool foo : 1;'.
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'.
53 - C99 allows the use of (_Bool)0.0 in constant expressions, but
54 this substitute cannot always provide this property.
56 Also, it is suggested that programs use 'bool' rather than '_Bool';
57 this isn't required, but 'bool' is more common. */
60 /* 7.16. Boolean type and values */
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
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@
84 typedef 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@
111 typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
112 # endif
113 # endif
114 #endif
115 #define bool _Bool
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
122 #endif /* _GL_STDBOOL_H */