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