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stddef.h.0p (3604B)


  1. '\" et
  2. .TH stddef.h "0P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
  3. .\"
  4. .SH PROLOG
  5. This manual page is part of the POSIX Programmer's Manual.
  6. The Linux implementation of this interface may differ (consult
  7. the corresponding Linux manual page for details of Linux behavior),
  8. or the interface may not be implemented on Linux.
  9. .\"
  10. .SH NAME
  11. stddef.h
  12. \(em standard type definitions
  13. .SH SYNOPSIS
  14. .LP
  15. .nf
  16. #include <stddef.h>
  17. .fi
  18. .SH DESCRIPTION
  19. The functionality described on this reference page is aligned with the
  20. ISO\ C standard. Any conflict between the requirements described here and the
  21. ISO\ C standard is unintentional. This volume of POSIX.1\(hy2017 defers to the ISO\ C standard.
  22. .P
  23. The
  24. .IR <stddef.h>
  25. header shall define the following macros:
  26. .IP NULL 10
  27. Null pointer constant.
  28. The macro shall expand to an integer constant expression with the
  29. value 0 cast to type
  30. .BR "void *" .
  31. .IP "offsetof(\fItype\fP, \fImember-designator\fP)" 10
  32. .br
  33. Integer constant expression of type
  34. .BR size_t ,
  35. the value of which is the offset in bytes to the structure member
  36. (\fImember-designator\fP), from the beginning of its structure
  37. (\fItype\fP).
  38. .P
  39. The
  40. .IR <stddef.h>
  41. header shall define the following types:
  42. .IP "\fBptrdiff_t\fP" 10
  43. Signed integer type of the result of subtracting two pointers.
  44. .IP "\fBwchar_t\fP" 10
  45. Integer type whose range of values can represent distinct codes for
  46. all members of the largest extended character set specified among the
  47. supported locales; the null character shall have the code value zero. Each
  48. member of the basic character set shall have a code value equal to its
  49. value when used as the lone character in an integer character constant
  50. if an implementation does not define _\|_STDC_MB_MIGHT_NEQ_WC_\|_.
  51. .IP "\fBsize_t\fP" 10
  52. Unsigned integer type of the result of the
  53. .IR sizeof
  54. operator.
  55. .P
  56. The implementation shall support one or more programming environments
  57. in which the widths of
  58. .BR ptrdiff_t ,
  59. .BR size_t ,
  60. and
  61. .BR wchar_t
  62. are no greater than the width of type
  63. .BR long .
  64. The names of these programming environments can be obtained using the
  65. \fIconfstr\fR()
  66. function or the
  67. .IR getconf
  68. utility.
  69. .LP
  70. .IR "The following sections are informative."
  71. .SH "APPLICATION USAGE"
  72. None.
  73. .SH RATIONALE
  74. The ISO\ C standard does not require the NULL macro to include the cast to type
  75. .BR "void *"
  76. and specifies that the NULL macro be implementation-defined. POSIX.1\(hy2008
  77. requires the cast and therefore need not be implementation-defined.
  78. .SH "FUTURE DIRECTIONS"
  79. None.
  80. .SH "SEE ALSO"
  81. .IR "\fB<sys_types.h>\fP",
  82. .IR "\fB<wchar.h>\fP"
  83. .P
  84. The System Interfaces volume of POSIX.1\(hy2017,
  85. .IR "\fIconfstr\fR\^(\|)"
  86. .P
  87. The Shell and Utilities volume of POSIX.1\(hy2017,
  88. .IR "\fIgetconf\fR\^"
  89. .\"
  90. .SH COPYRIGHT
  91. Portions of this text are reprinted and reproduced in electronic form
  92. from IEEE Std 1003.1-2017, Standard for Information Technology
  93. -- Portable Operating System Interface (POSIX), The Open Group Base
  94. Specifications Issue 7, 2018 Edition,
  95. Copyright (C) 2018 by the Institute of
  96. Electrical and Electronics Engineers, Inc and The Open Group.
  97. In the event of any discrepancy between this version and the original IEEE and
  98. The Open Group Standard, the original IEEE and The Open Group Standard
  99. is the referee document. The original Standard can be obtained online at
  100. http://www.opengroup.org/unix/online.html .
  101. .PP
  102. Any typographical or formatting errors that appear
  103. in this page are most likely
  104. to have been introduced during the conversion of the source files to
  105. man page format. To report such errors, see
  106. https://www.kernel.org/doc/man-pages/reporting_bugs.html .