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 } 31 32 /** 33 * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union 34 * 35 * @TYPE: The type of each flexible array element 36 * @NAME: The name of the flexible array member 37 * 38 * In order to have a flexible array member in a union or alone in a 39 * struct, it needs to be wrapped in an anonymous struct with at least 1 40 * named member, but that member can be empty. 41 */ 42 #define __DECLARE_FLEX_ARRAY(TYPE, NAME) \ 43 struct { \ 44 struct { } __empty_ ## NAME; \ 45 TYPE NAME[]; \ 46 } 47 #endif 48