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    1: /* Copyright (C) 2001-2003, 2006-2008 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, write to the Free Software Foundation,
   16:    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
   17: 
   18: #ifndef _GL_STDBOOL_H
   19: #define _GL_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:        - Bit-fields of type 'bool' are not supported.  Portable code
   45:          should use 'unsigned int foo : 1;' rather than 'bool foo : 1;'.
   46: 
   47:        - In C99, casts and automatic conversions to '_Bool' or 'bool' are
   48:          performed in such a way that every nonzero value gets converted
   49:          to 'true', and zero gets converted to 'false'.  This doesn't work
   50:          with this substitute.  With this substitute, only the values 0 and 1
   51:          give the expected result when converted to _Bool' or 'bool'.
   52: 
   53:    Also, it is suggested that programs use 'bool' rather than '_Bool';
   54:    this isn't required, but 'bool' is more common.  */
   55: 
   56: 
   57: /* 7.16. Boolean type and values */
   58: 
   59: /* BeOS <sys/socket.h> already #defines false 0, true 1.  We use the same
   60:    definitions below, but temporarily we have to #undef them.  */
   61: #if defined __BEOS__ && !defined __HAIKU__
   62: # include <OS.h> /* defines bool but not _Bool */
   63: # undef false
   64: # undef true
   65: #endif
   66: 
   67: /* For the sake of symbolic names in gdb, we define true and false as
   68:    enum constants, not only as macros.
   69:    It is tempting to write
   70:       typedef enum { false = 0, true = 1 } _Bool;
   71:    so that gdb prints values of type 'bool' symbolically. But if we do
   72:    this, values of type '_Bool' may promote to 'int' or 'unsigned int'
   73:    (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
   74:    (see ISO C 99 6.3.1.1.(2)).  So we add a negative value to the
   75:    enum; this ensures that '_Bool' promotes to 'int'.  */
   76: #if defined __cplusplus || (defined __BEOS__ && !defined __HAIKU__)
   77:   /* A compiler known to have 'bool'.  */
   78:   /* If the compiler already has both 'bool' and '_Bool', we can assume they
   79:      are the same types.  */
   80: # if !@HAVE__BOOL@
   81: typedef bool _Bool;
   82: # endif
   83: #else
   84: # if !defined __GNUC__
   85:    /* If @HAVE__BOOL@:
   86:         Some HP-UX cc and AIX IBM C compiler versions have compiler bugs when
   87:         the built-in _Bool type is used.  See
   88:           http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
   89:           http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
   90:           http://lists.gnu.org/archive/html/bug-coreutils/2005-10/msg00086.html
   91:         Similar bugs are likely with other compilers as well; this file
   92:         wouldn't be used if <stdbool.h> was working.
   93:         So we override the _Bool type.
   94:       If !@HAVE__BOOL@:
   95:         Need to define _Bool ourselves. As 'signed char' or as an enum type?
   96:         Use of a typedef, with SunPRO C, leads to a stupid
   97:           "warning: _Bool is a keyword in ISO C99".
   98:         Use of an enum type, with IRIX cc, leads to a stupid
   99:           "warning(1185): enumerated type mixed with another type".
  100:         Even the existence of an enum type, without a typedef,
  101:           "Invalid enumerator. (badenum)" with HP-UX cc on Tru64.
  102:         The only benefit of the enum, debuggability, is not important
  103:         with these compilers.  So use 'signed char' and no enum.  */
  104: #  define _Bool signed char
  105: # else
  106:    /* With this compiler, trust the _Bool type if the compiler has it.  */
  107: #  if !@HAVE__BOOL@
  108: typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
  109: #  endif
  110: # endif
  111: #endif
  112: #define bool _Bool
  113: 
  114: /* The other macros must be usable in preprocessor directives.  */
  115: #define false 0
  116: #define true 1
  117: #define __bool_true_false_are_defined 1
  118: 
  119: #endif /* _GL_STDBOOL_H */