1 /* Copyright (C) 2001-2003, 2006-2012 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, 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@ 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 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