lib/stdbool_.h

   1 /* Copyright (C) 2001, 2002, 2003, 2006 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 2, 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 _STDBOOL_H
  19 #define _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        - In C99, casts and automatic conversions to '_Bool' or 'bool' are
  45          performed in such a way that every nonzero value gets converted
  46          to 'true', and zero gets converted to 'false'.  This doesn't work
  47          with this substitute.  With this substitute, only the values 0 and 1
  48          give the expected result when converted to _Bool' or 'bool'.
  49
  50    Also, it is suggested that programs use 'bool' rather than '_Bool';
  51    this isn't required, but 'bool' is more common.  */
  52
  53
  54 /* 7.16. Boolean type and values */
  55
  56 /* BeOS <sys/socket.h> already #defines false 0, true 1.  We use the same
  57    definitions below, but temporarily we have to #undef them.  */
  58 #ifdef __BEOS__
  59 # include <OS.h> /* defines bool but not _Bool */
  60 # undef false
  61 # undef true
  62 #endif
  63
  64 /* For the sake of symbolic names in gdb, we define true and false as
  65    enum constants, not only as macros.
  66    It is tempting to write
  67       typedef enum { false = 0, true = 1 } _Bool;
  68    so that gdb prints values of type 'bool' symbolically. But if we do
  69    this, values of type '_Bool' may promote to 'int' or 'unsigned int'
  70    (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
  71    (see ISO C 99 6.3.1.1.(2)).  So we add a negative value to the
  72    enum; this ensures that '_Bool' promotes to 'int'.  */
  73 #if defined __cplusplus || defined __BEOS__
  74   /* A compiler known to have 'bool'.  */
  75   /* If the compiler already has both 'bool' and '_Bool', we can assume they
  76      are the same types.  */
  77 # if !@HAVE__BOOL@
  78 typedef bool _Bool;
  79 # endif
  80 #else
  81 # if !defined __GNUC__
  82    /* If @HAVE__BOOL@:
  83         Some HP-UX cc and AIX IBM C compiler versions have compiler bugs when
  84         the built-in _Bool type is used.  See
  85           http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
  86           http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
  87           http://lists.gnu.org/archive/html/bug-coreutils/2005-10/msg00086.html
  88         Similar bugs are likely with other compilers as well; this file
  89         wouldn't be used if <stdbool.h> was working.
  90         So we override the _Bool type.
  91       If !@HAVE__BOOL@:
  92         Need to define _Bool ourselves. As 'signed char' or as an enum type?
  93         Use of a typedef, with SunPRO C, leads to a stupid
  94           "warning: _Bool is a keyword in ISO C99".
  95         Use of an enum type, with IRIX cc, leads to a stupid
  96           "warning(1185): enumerated type mixed with another type".
  97         The only benefit of the enum type, debuggability, is not important
  98         with these compilers.  So use 'signed char' and no typedef.  */
  99 #  define _Bool signed char
 100 enum { false = 0, true = 1 };
 101 # else
 102    /* With this compiler, trust the _Bool type if the compiler has it.  */
 103 #  if !@HAVE__BOOL@
 104 typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
 105 #  endif
 106 # endif
 107 #endif
 108 #define bool _Bool
 109
 110 /* The other macros must be usable in preprocessor directives.  */
 111 #define false 0
 112 #define true 1
 113 #define __bool_true_false_are_defined 1
 114
 115 #endif /* _STDBOOL_H */