LXR linux/include/linux/stddef.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef _LINUX_STDDEF_H
   3#define _LINUX_STDDEF_H
   4
   5#include <uapi/linux/stddef.h>
   6
   7#undef NULL
   8#define NULL ((void *)0)
   9
  10enum {
  11        false   = 0,
  12        true    = 1
  13};
  14
  15#undef offsetof
  16#define offsetof(TYPE, MEMBER)  __builtin_offsetof(TYPE, MEMBER)
  17
  18/**
  19 * sizeof_field() - Report the size of a struct field in bytes
  20 *
  21 * @TYPE: The structure containing the field of interest
  22 * @MEMBER: The field to return the size of
  23 */
  24#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
  25
  26/**
  27 * offsetofend() - Report the offset of a struct field within the struct
  28 *
  29 * @TYPE: The type of the structure
  30 * @MEMBER: The member within the structure to get the end offset of
  31 */
  32#define offsetofend(TYPE, MEMBER) \
  33        (offsetof(TYPE, MEMBER) + sizeof_field(TYPE, MEMBER))
  34
  35/**
  36 * struct_group() - Wrap a set of declarations in a mirrored struct
  37 *
  38 * @NAME: The identifier name of the mirrored sub-struct
  39 * @MEMBERS: The member declarations for the mirrored structs
  40 *
  41 * Used to create an anonymous union of two structs with identical
  42 * layout and size: one anonymous and one named. The former can be
  43 * used normally without sub-struct naming, and the latter can be
  44 * used to reason about the start, end, and size of the group of
  45 * struct members.
  46 */
  47#define struct_group(NAME, MEMBERS...)  \
  48        __struct_group(/* no tag */, NAME, /* no attrs */, MEMBERS)
  49
  50/**
  51 * struct_group_attr() - Create a struct_group() with trailing attributes
  52 *
  53 * @NAME: The identifier name of the mirrored sub-struct
  54 * @ATTRS: Any struct attributes to apply
  55 * @MEMBERS: The member declarations for the mirrored structs
  56 *
  57 * Used to create an anonymous union of two structs with identical
  58 * layout and size: one anonymous and one named. The former can be
  59 * used normally without sub-struct naming, and the latter can be
  60 * used to reason about the start, end, and size of the group of
  61 * struct members. Includes structure attributes argument.
  62 */
  63#define struct_group_attr(NAME, ATTRS, MEMBERS...) \
  64        __struct_group(/* no tag */, NAME, ATTRS, MEMBERS)
  65
  66/**
  67 * struct_group_tagged() - Create a struct_group with a reusable tag
  68 *
  69 * @TAG: The tag name for the named sub-struct
  70 * @NAME: The identifier name of the mirrored sub-struct
  71 * @MEMBERS: The member declarations for the mirrored structs
  72 *
  73 * Used to create an anonymous union of two structs with identical
  74 * layout and size: one anonymous and one named. The former can be
  75 * used normally without sub-struct naming, and the latter can be
  76 * used to reason about the start, end, and size of the group of
  77 * struct members. Includes struct tag argument for the named copy,
  78 * so the specified layout can be reused later.
  79 */
  80#define struct_group_tagged(TAG, NAME, MEMBERS...) \
  81        __struct_group(TAG, NAME, /* no attrs */, MEMBERS)
  82
  83/**
  84 * DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
  85 *
  86 * @TYPE: The type of each flexible array element
  87 * @NAME: The name of the flexible array member
  88 *
  89 * In order to have a flexible array member in a union or alone in a
  90 * struct, it needs to be wrapped in an anonymous struct with at least 1
  91 * named member, but that member can be empty.
  92 */
  93#define DECLARE_FLEX_ARRAY(TYPE, NAME) \
  94        __DECLARE_FLEX_ARRAY(TYPE, NAME)
  95
  96#endif
  97