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 /** 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 /* _LINUX_STDDEF_H */ 59