1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2#ifndef _LINUX_STDDEF_H
3#define _LINUX_STDDEF_H
4
5
6
7#ifndef __always_inline
8#define __always_inline __inline__
9#endif
10
11/* Not all C++ standards support type declarations inside an anonymous union */
12#ifndef __cplusplus
13#define __struct_group_tag(TAG) TAG
14#else
15#define __struct_group_tag(TAG)
16#endif
17
18/**
19 * __struct_group() - Create a mirrored named and anonyomous struct
20 *
21 * @TAG: The tag name for the named sub-struct (usually empty)
22 * @NAME: The identifier name of the mirrored sub-struct
23 * @ATTRS: Any struct attributes (usually empty)
24 * @MEMBERS: The member declarations for the mirrored structs
25 *
26 * Used to create an anonymous union of two structs with identical layout
27 * and size: one anonymous and one named. The former's members can be used
28 * normally without sub-struct naming, and the latter can be used to
29 * reason about the start, end, and size of the group of struct members.
30 * The named struct can also be explicitly tagged for layer reuse (C only),
31 * as well as both having struct attributes appended.
32 */
33#define __struct_group(TAG, NAME, ATTRS, MEMBERS...) \
34 union { \
35 struct { MEMBERS } ATTRS; \
36 struct __struct_group_tag(TAG) { MEMBERS } ATTRS NAME; \
37 } ATTRS
38
39#ifdef __cplusplus
40/* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */
41#define __DECLARE_FLEX_ARRAY(T, member) \
42 T member[0]
43#else
44/**
45 * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
46 *
47 * @TYPE: The type of each flexible array element
48 * @NAME: The name of the flexible array member
49 *
50 * In order to have a flexible array member in a union or alone in a
51 * struct, it needs to be wrapped in an anonymous struct with at least 1
52 * named member, but that member can be empty.
53 */
54#define __DECLARE_FLEX_ARRAY(TYPE, NAME) \
55 struct { \
56 struct { } __empty_ ## NAME; \
57 TYPE NAME[]; \
58 }
59#endif
60
61#ifndef __counted_by
62#define __counted_by(m)
63#endif
64
65#endif /* _LINUX_STDDEF_H */
66