stdbool.in.h 4.8 KB

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