00001 /* Copyright (C) 2001, 2002, 2003, 2006, 2007 Free Software Foundation, Inc. 00002 Written by Bruno Haible <haible@clisp.cons.org>, 2001. 00003 00004 This program is free software; you can redistribute it and/or modify 00005 it under the terms of the GNU Lesser General Public License as published by 00006 the Free Software Foundation; either version 2.1, or (at your option) 00007 any later version. 00008 00009 This program is distributed in the hope that it will be useful, 00010 but WITHOUT ANY WARRANTY; without even the implied warranty of 00011 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00012 GNU Lesser General Public License for more details. 00013 00014 You should have received a copy of the GNU Lesser General Public License 00015 along with this program; if not, write to the Free Software Foundation, 00016 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ 00017 00018 #ifndef _GL_STDBOOL_H 00019 #define _GL_STDBOOL_H 00020 00021 /* ISO C 99 <stdbool.h> for platforms that lack it. */ 00022 00023 /* Usage suggestions: 00024 00025 Programs that use <stdbool.h> should be aware of some limitations 00026 and standards compliance issues. 00027 00028 Standards compliance: 00029 00030 - <stdbool.h> must be #included before 'bool', 'false', 'true' 00031 can be used. 00032 00033 - You cannot assume that sizeof (bool) == 1. 00034 00035 - Programs should not undefine the macros bool, true, and false, 00036 as C99 lists that as an "obsolescent feature". 00037 00038 Limitations of this substitute, when used in a C89 environment: 00039 00040 - <stdbool.h> must be #included before the '_Bool' type can be used. 00041 00042 - You cannot assume that _Bool is a typedef; it might be a macro. 00043 00044 - Bit-fields of type 'bool' are not supported. Portable code 00045 should use 'unsigned int foo : 1;' rather than 'bool foo : 1;'. 00046 00047 - In C99, casts and automatic conversions to '_Bool' or 'bool' are 00048 performed in such a way that every nonzero value gets converted 00049 to 'true', and zero gets converted to 'false'. This doesn't work 00050 with this substitute. With this substitute, only the values 0 and 1 00051 give the expected result when converted to _Bool' or 'bool'. 00052 00053 Also, it is suggested that programs use 'bool' rather than '_Bool'; 00054 this isn't required, but 'bool' is more common. */ 00055 00056 00057 /* 7.16. Boolean type and values */ 00058 00059 /* BeOS <sys/socket.h> already #defines false 0, true 1. We use the same 00060 definitions below, but temporarily we have to #undef them. */ 00061 #ifdef __BEOS__ 00062 # include <OS.h> /* defines bool but not _Bool */ 00063 # undef false 00064 # undef true 00065 #endif 00066 00067 /* For the sake of symbolic names in gdb, we define true and false as 00068 enum constants, not only as macros. 00069 It is tempting to write 00070 typedef enum { false = 0, true = 1 } _Bool; 00071 so that gdb prints values of type 'bool' symbolically. But if we do 00072 this, values of type '_Bool' may promote to 'int' or 'unsigned int' 00073 (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int' 00074 (see ISO C 99 6.3.1.1.(2)). So we add a negative value to the 00075 enum; this ensures that '_Bool' promotes to 'int'. */ 00076 #if defined __cplusplus || defined __BEOS__ 00077 /* A compiler known to have 'bool'. */ 00078 /* If the compiler already has both 'bool' and '_Bool', we can assume they 00079 are the same types. */ 00080 # if !@HAVE__BOOL@ 00081 typedef bool _Bool; 00082 # endif 00083 #else 00084 # if !defined __GNUC__ 00085 /* If @HAVE__BOOL@: 00086 Some HP-UX cc and AIX IBM C compiler versions have compiler bugs when 00087 the built-in _Bool type is used. See 00088 http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html 00089 http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html 00090 http://lists.gnu.org/archive/html/bug-coreutils/2005-10/msg00086.html 00091 Similar bugs are likely with other compilers as well; this file 00092 wouldn't be used if <stdbool.h> was working. 00093 So we override the _Bool type. 00094 If !@HAVE__BOOL@: 00095 Need to define _Bool ourselves. As 'signed char' or as an enum type? 00096 Use of a typedef, with SunPRO C, leads to a stupid 00097 "warning: _Bool is a keyword in ISO C99". 00098 Use of an enum type, with IRIX cc, leads to a stupid 00099 "warning(1185): enumerated type mixed with another type". 00100 Even the existence of an enum type, without a typedef, 00101 "Invalid enumerator. (badenum)" with HP-UX cc on Tru64. 00102 The only benefit of the enum, debuggability, is not important 00103 with these compilers. So use 'signed char' and no enum. */ 00104 # define _Bool signed char 00105 # else 00106 /* With this compiler, trust the _Bool type if the compiler has it. */ 00107 # if !@HAVE__BOOL@ 00108 typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool; 00109 # endif 00110 # endif 00111 #endif 00112 #define bool _Bool 00113 00114 /* The other macros must be usable in preprocessor directives. */ 00115 #define false 0 00116 #define true 1 00117 #define __bool_true_false_are_defined 1 00118 00119 #endif /* _GL_STDBOOL_H */