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
10 enum {
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
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