lib/stdbool.in.h

   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, see <http://www.gnu.org/licenses/>.  */
  16
  17 #ifndef _GL_STDBOOL_H
  18 #define _GL_STDBOOL_H
  19
  20 /* ISO C 99 <stdbool.h> for platforms that lack it.  */
  21
  22 /* Usage suggestions:
  23
  24    Programs that use <stdbool.h> should be aware of some limitations
  25    and standards compliance issues.
  26
  27    Standards compliance:
  28
  29        - <stdbool.h> must be #included before 'bool', 'false', 'true'
  30          can be used.
  31
  32        - You cannot assume that sizeof (bool) == 1.
  33
  34        - Programs should not undefine the macros bool, true, and false,
  35          as C99 lists that as an "obsolescent feature".
  36
  37    Limitations of this substitute, when used in a C89 environment:
  38
  39        - <stdbool.h> must be #included before the '_Bool' type can be used.
  40
  41        - You cannot assume that _Bool is a typedef; it might be a macro.
  42
  43        - Bit-fields of type 'bool' are not supported.  Portable code
  44          should use 'unsigned int foo : 1;' rather than 'bool foo : 1;'.
  45
  46        - In C99, casts and automatic conversions to '_Bool' or 'bool' are
  47          performed in such a way that every nonzero value gets converted
  48          to 'true', and zero gets converted to 'false'.  This doesn't work
  49          with this substitute.  With this substitute, only the values 0 and 1
  50          give the expected result when converted to _Bool' or 'bool'.
  51
  52        - C99 allows the use of (_Bool)0.0 in constant expressions, but
  53          this substitute cannot always provide this property.
  54
  55    Also, it is suggested that programs use 'bool' rather than '_Bool';
  56    this isn't required, but 'bool' is more common.  */
  57
  58
  59 /* 7.16. Boolean type and values */
  60
  61 /* BeOS <sys/socket.h> already #defines false 0, true 1.  We use the same
  62    definitions below, but temporarily we have to #undef them.  */
  63 #if defined __BEOS__ && !defined __HAIKU__
  64 # include <OS.h> /* defines bool but not _Bool */
  65 # undef false
  66 # undef true
  67 #endif
  68
  69 /* For the sake of symbolic names in gdb, we define true and false as
  70    enum constants, not only as macros.
  71    It is tempting to write
  72       typedef enum { false = 0, true = 1 } _Bool;
  73    so that gdb prints values of type 'bool' symbolically. But if we do
  74    this, values of type '_Bool' may promote to 'int' or 'unsigned int'
  75    (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
  76    (see ISO C 99 6.3.1.1.(2)).  So we add a negative value to the
  77    enum; this ensures that '_Bool' promotes to 'int'.  */
  78 #if defined __cplusplus || (defined __BEOS__ && !defined __HAIKU__)
  79   /* A compiler known to have 'bool'.  */
  80   /* If the compiler already has both 'bool' and '_Bool', we can assume they
  81      are the same types.  */
  82 # if !@HAVE__BOOL@
  83 typedef bool _Bool;
  84 # endif
  85 #else
  86 # if !defined __GNUC__
  87    /* If @HAVE__BOOL@:
  88         Some HP-UX cc and AIX IBM C compiler versions have compiler bugs when
  89         the built-in _Bool type is used.  See
  90           http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
  91           http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
  92           http://lists.gnu.org/archive/html/bug-coreutils/2005-10/msg00086.html
  93         Similar bugs are likely with other compilers as well; this file
  94         wouldn't be used if <stdbool.h> was working.
  95         So we override the _Bool type.
  96       If !@HAVE__BOOL@:
  97         Need to define _Bool ourselves. As 'signed char' or as an enum type?
  98         Use of a typedef, with SunPRO C, leads to a stupid
  99           "warning: _Bool is a keyword in ISO C99".
 100         Use of an enum type, with IRIX cc, leads to a stupid
 101           "warning(1185): enumerated type mixed with another type".
 102         Even the existence of an enum type, without a typedef,
 103           "Invalid enumerator. (badenum)" with HP-UX cc on Tru64.
 104         The only benefit of the enum, debuggability, is not important
 105         with these compilers.  So use 'signed char' and no enum.  */
 106 #  define _Bool signed char
 107 # else
 108    /* With this compiler, trust the _Bool type if the compiler has it.  */
 109 #  if !@HAVE__BOOL@
 110 typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
 111 #  endif
 112 # endif
 113 #endif
 114 #define bool _Bool
 115
 116 /* The other macros must be usable in preprocessor directives.  */
 117 #define false 0
 118 #define true 1
 119 #define __bool_true_false_are_defined 1
 120
 121 #endif /* _GL_STDBOOL_H */