/* Copyright (C) 2001, 2002, 2003, 2005 Free Software Foundation, Inc. Written by Bruno Haible , 2001. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ #ifndef _STDBOOL_H #define _STDBOOL_H /* ISO C 99 for platforms that lack it. */ /* Usage suggestions: Programs that use should be aware of some limitations and standards compliance issues. Standards compliance: - must be #included before 'bool', 'false', 'true' can be used. - You cannot assume that sizeof (bool) == 1. - Programs should not undefine the macros bool, true, and false, as C99 lists that as an "obsolescent feature". Limitations of this substitute, when used in a C89 environment: - must be #included before the '_Bool' type can be used. - You cannot assume that _Bool is a typedef; it might be a macro. - In C99, casts and automatic conversions to '_Bool' or 'bool' are performed in such a way that every nonzero value gets converted to 'true', and zero gets converted to 'false'. This doesn't work with this substitute. With this substitute, only the values 0 and 1 give the expected result when converted to _Bool' or 'bool'. Also, it is suggested that programs use 'bool' rather than '_Bool'; this isn't required, but 'bool' is more common. */ /* 7.16. Boolean type and values */ /* BeOS already #defines false 0, true 1. We use the same definitions below, which is OK. */ #ifdef __BEOS__ # include /* defines bool but not _Bool */ #endif /* C++ and BeOS have a reliable _Bool. Otherwise, since this file is being compiled, the system is not reliable so assume that the system _Bool is not reliable either. Under that assumption, it is tempting to write typedef enum { false, true } _Bool; so that gdb prints values of type 'bool' symbolically. But if we do this, values of type '_Bool' may promote to 'int' or 'unsigned int' (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int' (see ISO C 99 6.3.1.1.(2)). We could instead try this: typedef enum { _Bool_dummy = -1, false, true } _Bool; as the negative value ensures that '_Bool' promotes to 'int'. However, this runs into some other problems. First, Sun's C compiler when (__SUNPRO_C < 0x550 || __STDC__ == 1) issues a stupid "warning: _Bool is a keyword in ISO C99". Second, IBM's AIX cc compiler 6.0.0.0 (and presumably other versions) mishandles subscripts involving _Bool (effectively, _Bool promotes to unsigned int in this case), and we need to redefine _Bool in that case. Third, HP-UX 10.20's C compiler lacks but has _Bool and mishandles comparisons of _Bool to int (it promotes _Bool to unsigned int). The simplest way to work around these problems is to ignore any existing definition of _Bool and use our own. */ #if defined __cplusplus || defined __BEOS__ typedef bool _Bool; #else # define _Bool signed char #endif #define bool _Bool /* The other macros must be usable in preprocessor directives. */ #define false 0 #define true 1 #define __bool_true_false_are_defined 1 #endif /* _STDBOOL_H */