stddef.h (2107B) - Raw
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 #ifndef __counted_by_le 66 #define __counted_by_le(m) 67 #endif 68 69 #ifndef __counted_by_be 70 #define __counted_by_be(m) 71 #endif 72 73 #endif /* _LINUX_STDDEF_H */