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123 lines
4.9 KiB
C
123 lines
4.9 KiB
C
/* Copyright (C) 2001-2003, 2006-2011 Free Software Foundation, Inc.
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Written by Bruno Haible <haible@clisp.cons.org>, 2001.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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#ifndef _GL_STDBOOL_H
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#define _GL_STDBOOL_H
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/* ISO C 99 <stdbool.h> for platforms that lack it. */
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/* Usage suggestions:
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Programs that use <stdbool.h> should be aware of some limitations
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and standards compliance issues.
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Standards compliance:
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- <stdbool.h> must be #included before 'bool', 'false', 'true'
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can be used.
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- You cannot assume that sizeof (bool) == 1.
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- Programs should not undefine the macros bool, true, and false,
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as C99 lists that as an "obsolescent feature".
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Limitations of this substitute, when used in a C89 environment:
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- <stdbool.h> must be #included before the '_Bool' type can be used.
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- You cannot assume that _Bool is a typedef; it might be a macro.
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- Bit-fields of type 'bool' are not supported. Portable code
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should use 'unsigned int foo : 1;' rather than 'bool foo : 1;'.
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- In C99, casts and automatic conversions to '_Bool' or 'bool' are
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performed in such a way that every nonzero value gets converted
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to 'true', and zero gets converted to 'false'. This doesn't work
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with this substitute. With this substitute, only the values 0 and 1
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give the expected result when converted to _Bool' or 'bool'.
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- C99 allows the use of (_Bool)0.0 in constant expressions, but
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this substitute cannot always provide this property.
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Also, it is suggested that programs use 'bool' rather than '_Bool';
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this isn't required, but 'bool' is more common. */
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/* 7.16. Boolean type and values */
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/* BeOS <sys/socket.h> already #defines false 0, true 1. We use the same
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definitions below, but temporarily we have to #undef them. */
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#if defined __BEOS__ && !defined __HAIKU__
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# include <OS.h> /* defines bool but not _Bool */
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# undef false
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# undef true
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#endif
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/* For the sake of symbolic names in gdb, we define true and false as
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enum constants, not only as macros.
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It is tempting to write
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typedef enum { false = 0, true = 1 } _Bool;
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so that gdb prints values of type 'bool' symbolically. But if we do
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this, values of type '_Bool' may promote to 'int' or 'unsigned int'
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(see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
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(see ISO C 99 6.3.1.1.(2)). So we add a negative value to the
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enum; this ensures that '_Bool' promotes to 'int'. */
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#if defined __cplusplus || (defined __BEOS__ && !defined __HAIKU__)
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/* A compiler known to have 'bool'. */
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/* If the compiler already has both 'bool' and '_Bool', we can assume they
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are the same types. */
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# if !@HAVE__BOOL@
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typedef bool _Bool;
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# endif
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#else
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# if !defined __GNUC__
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/* If @HAVE__BOOL@:
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Some HP-UX cc and AIX IBM C compiler versions have compiler bugs when
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the built-in _Bool type is used. See
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http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
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http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
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http://lists.gnu.org/archive/html/bug-coreutils/2005-10/msg00086.html
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Similar bugs are likely with other compilers as well; this file
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wouldn't be used if <stdbool.h> was working.
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So we override the _Bool type.
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If !@HAVE__BOOL@:
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Need to define _Bool ourselves. As 'signed char' or as an enum type?
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Use of a typedef, with SunPRO C, leads to a stupid
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"warning: _Bool is a keyword in ISO C99".
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Use of an enum type, with IRIX cc, leads to a stupid
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"warning(1185): enumerated type mixed with another type".
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Even the existence of an enum type, without a typedef,
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"Invalid enumerator. (badenum)" with HP-UX cc on Tru64.
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The only benefit of the enum, debuggability, is not important
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with these compilers. So use 'signed char' and no enum. */
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# define _Bool signed char
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# else
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/* With this compiler, trust the _Bool type if the compiler has it. */
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# if !@HAVE__BOOL@
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typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
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# endif
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# endif
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#endif
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#define bool _Bool
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/* The other macros must be usable in preprocessor directives. */
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#define false 0
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#define true 1
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#define __bool_true_false_are_defined 1
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#endif /* _GL_STDBOOL_H */
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