xref: /openbmc/linux/include/uapi/linux/stddef.h (revision 4b81d155)
1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2 #ifndef _UAPI_LINUX_STDDEF_H
3 #define _UAPI_LINUX_STDDEF_H
4 
5 #include <linux/compiler_types.h>
6 
7 #ifndef __always_inline
8 #define __always_inline inline
9 #endif
10 
11 /**
12  * __struct_group() - Create a mirrored named and anonyomous struct
13  *
14  * @TAG: The tag name for the named sub-struct (usually empty)
15  * @NAME: The identifier name of the mirrored sub-struct
16  * @ATTRS: Any struct attributes (usually empty)
17  * @MEMBERS: The member declarations for the mirrored structs
18  *
19  * Used to create an anonymous union of two structs with identical layout
20  * and size: one anonymous and one named. The former's members can be used
21  * normally without sub-struct naming, and the latter can be used to
22  * reason about the start, end, and size of the group of struct members.
23  * The named struct can also be explicitly tagged for layer reuse, as well
24  * as both having struct attributes appended.
25  */
26 #define __struct_group(TAG, NAME, ATTRS, MEMBERS...) \
27 	union { \
28 		struct { MEMBERS } ATTRS; \
29 		struct TAG { MEMBERS } ATTRS NAME; \
30 	} ATTRS
31 
32 #ifdef __cplusplus
33 /* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */
34 #define __DECLARE_FLEX_ARRAY(T, member)	\
35 	T member[0]
36 #else
37 /**
38  * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
39  *
40  * @TYPE: The type of each flexible array element
41  * @NAME: The name of the flexible array member
42  *
43  * In order to have a flexible array member in a union or alone in a
44  * struct, it needs to be wrapped in an anonymous struct with at least 1
45  * named member, but that member can be empty.
46  */
47 #define __DECLARE_FLEX_ARRAY(TYPE, NAME)	\
48 	struct { \
49 		struct { } __empty_ ## NAME; \
50 		TYPE NAME[]; \
51 	}
52 #endif
53 
54 #ifndef __counted_by
55 #define __counted_by(m)
56 #endif
57 
58 #endif /* _UAPI_LINUX_STDDEF_H */
59