stdbool_.h 4.5 KB

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  1. /* Copyright (C) 2001, 2002, 2003, 2006 Free Software Foundation, Inc.
  2. Written by Bruno Haible <haible@clisp.cons.org>, 2001.
  3. This program is free software; you can redistribute it and/or modify
  4. it under the terms of the GNU General Public License as published by
  5. the Free Software Foundation; either version 2, or (at your option)
  6. any later version.
  7. This program is distributed in the hope that it will be useful,
  8. but WITHOUT ANY WARRANTY; without even the implied warranty of
  9. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  10. GNU General Public License for more details.
  11. You should have received a copy of the GNU General Public License
  12. along with this program; if not, write to the Free Software Foundation,
  13. Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
  14. #ifndef _STDBOOL_H
  15. #define _STDBOOL_H
  16. /* ISO C 99 <stdbool.h> for platforms that lack it. */
  17. /* Usage suggestions:
  18. Programs that use <stdbool.h> should be aware of some limitations
  19. and standards compliance issues.
  20. Standards compliance:
  21. - <stdbool.h> must be #included before 'bool', 'false', 'true'
  22. can be used.
  23. - You cannot assume that sizeof (bool) == 1.
  24. - Programs should not undefine the macros bool, true, and false,
  25. as C99 lists that as an "obsolescent feature".
  26. Limitations of this substitute, when used in a C89 environment:
  27. - <stdbool.h> must be #included before the '_Bool' type can be used.
  28. - You cannot assume that _Bool is a typedef; it might be a macro.
  29. - In C99, casts and automatic conversions to '_Bool' or 'bool' are
  30. performed in such a way that every nonzero value gets converted
  31. to 'true', and zero gets converted to 'false'. This doesn't work
  32. with this substitute. With this substitute, only the values 0 and 1
  33. give the expected result when converted to _Bool' or 'bool'.
  34. Also, it is suggested that programs use 'bool' rather than '_Bool';
  35. this isn't required, but 'bool' is more common. */
  36. /* 7.16. Boolean type and values */
  37. /* BeOS <sys/socket.h> already #defines false 0, true 1. We use the same
  38. definitions below, but temporarily we have to #undef them. */
  39. #ifdef __BEOS__
  40. # include <OS.h> /* defines bool but not _Bool */
  41. # undef false
  42. # undef true
  43. #endif
  44. /* For the sake of symbolic names in gdb, we define true and false as
  45. enum constants, not only as macros.
  46. It is tempting to write
  47. typedef enum { false = 0, true = 1 } _Bool;
  48. so that gdb prints values of type 'bool' symbolically. But if we do
  49. this, values of type '_Bool' may promote to 'int' or 'unsigned int'
  50. (see ISO C 99 6.7.2.2.(4)); however, '_Bool' must promote to 'int'
  51. (see ISO C 99 6.3.1.1.(2)). So we add a negative value to the
  52. enum; this ensures that '_Bool' promotes to 'int'. */
  53. #if defined __cplusplus || defined __BEOS__
  54. /* A compiler known to have 'bool'. */
  55. /* If the compiler already has both 'bool' and '_Bool', we can assume they
  56. are the same types. */
  57. # if !@HAVE__BOOL@
  58. typedef bool _Bool;
  59. # endif
  60. #else
  61. # if !defined __GNUC__
  62. /* If @HAVE__BOOL@:
  63. Some HP-UX cc and AIX IBM C compiler versions have compiler bugs when
  64. the built-in _Bool type is used. See
  65. http://gcc.gnu.org/ml/gcc-patches/2003-12/msg02303.html
  66. http://lists.gnu.org/archive/html/bug-coreutils/2005-11/msg00161.html
  67. http://lists.gnu.org/archive/html/bug-coreutils/2005-10/msg00086.html
  68. Similar bugs are likely with other compilers as well; this file
  69. wouldn't be used if <stdbool.h> was working.
  70. So we override the _Bool type.
  71. If !@HAVE__BOOL@:
  72. Need to define _Bool ourselves. As 'signed char' or as an enum type?
  73. Use of a typedef, with SunPRO C, leads to a stupid
  74. "warning: _Bool is a keyword in ISO C99".
  75. Use of an enum type, with IRIX cc, leads to a stupid
  76. "warning(1185): enumerated type mixed with another type".
  77. The only benefit of the enum type, debuggability, is not important
  78. with these compilers. So use 'signed char' and no typedef. */
  79. # define _Bool signed char
  80. enum { false = 0, true = 1 };
  81. # else
  82. /* With this compiler, trust the _Bool type if the compiler has it. */
  83. # if !@HAVE__BOOL@
  84. typedef enum { _Bool_must_promote_to_int = -1, false = 0, true = 1 } _Bool;
  85. # endif
  86. # endif
  87. #endif
  88. #define bool _Bool
  89. /* The other macros must be usable in preprocessor directives. */
  90. #define false 0
  91. #define true 1
  92. #define __bool_true_false_are_defined 1
  93. #endif /* _STDBOOL_H */