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