1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _LINUX_STDDEF_H 3 #define _LINUX_STDDEF_H 4 5 #include <uapi/linux/stddef.h> 6 7 #undef NULL 8 #define NULL ((void *)0) 9 10 enum { 11 false = 0, 12 true = 1 13 }; 14 15 #undef offsetof 16 #define offsetof(TYPE, MEMBER) __builtin_offsetof(TYPE, MEMBER) 17 18 /** 19 * sizeof_field() - Report the size of a struct field in bytes 20 * 21 * @TYPE: The structure containing the field of interest 22 * @MEMBER: The field to return the size of 23 */ 24 #define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER)) 25 26 /** 27 * offsetofend() - Report the offset of a struct field within the struct 28 * 29 * @TYPE: The type of the structure 30 * @MEMBER: The member within the structure to get the end offset of 31 */ 32 #define offsetofend(TYPE, MEMBER) \ 33 (offsetof(TYPE, MEMBER) + sizeof_field(TYPE, MEMBER)) 34 35 /** 36 * struct_group() - Wrap a set of declarations in a mirrored struct 37 * 38 * @NAME: The identifier name of the mirrored sub-struct 39 * @MEMBERS: The member declarations for the mirrored structs 40 * 41 * Used to create an anonymous union of two structs with identical 42 * layout and size: one anonymous and one named. The former can be 43 * used normally without sub-struct naming, and the latter can be 44 * used to reason about the start, end, and size of the group of 45 * struct members. 46 */ 47 #define struct_group(NAME, MEMBERS...) \ 48 __struct_group(/* no tag */, NAME, /* no attrs */, MEMBERS) 49 50 /** 51 * struct_group_attr() - Create a struct_group() with trailing attributes 52 * 53 * @NAME: The identifier name of the mirrored sub-struct 54 * @ATTRS: Any struct attributes to apply 55 * @MEMBERS: The member declarations for the mirrored structs 56 * 57 * Used to create an anonymous union of two structs with identical 58 * layout and size: one anonymous and one named. The former can be 59 * used normally without sub-struct naming, and the latter can be 60 * used to reason about the start, end, and size of the group of 61 * struct members. Includes structure attributes argument. 62 */ 63 #define struct_group_attr(NAME, ATTRS, MEMBERS...) \ 64 __struct_group(/* no tag */, NAME, ATTRS, MEMBERS) 65 66 /** 67 * struct_group_tagged() - Create a struct_group with a reusable tag 68 * 69 * @TAG: The tag name for the named sub-struct 70 * @NAME: The identifier name of the mirrored sub-struct 71 * @MEMBERS: The member declarations for the mirrored structs 72 * 73 * Used to create an anonymous union of two structs with identical 74 * layout and size: one anonymous and one named. The former can be 75 * used normally without sub-struct naming, and the latter can be 76 * used to reason about the start, end, and size of the group of 77 * struct members. Includes struct tag argument for the named copy, 78 * so the specified layout can be reused later. 79 */ 80 #define struct_group_tagged(TAG, NAME, MEMBERS...) \ 81 __struct_group(TAG, NAME, /* no attrs */, MEMBERS) 82 83 /** 84 * DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union 85 * 86 * @TYPE: The type of each flexible array element 87 * @NAME: The name of the flexible array member 88 * 89 * In order to have a flexible array member in a union or alone in a 90 * struct, it needs to be wrapped in an anonymous struct with at least 1 91 * named member, but that member can be empty. 92 */ 93 #define DECLARE_FLEX_ARRAY(TYPE, NAME) \ 94 __DECLARE_FLEX_ARRAY(TYPE, NAME) 95 96 /** 97 * TRAILING_OVERLAP() - Overlap a flexible-array member with trailing members. 98 * 99 * Creates a union between a flexible-array member (FAM) in a struct and a set 100 * of additional members that would otherwise follow it. 101 * 102 * @TYPE: Flexible structure type name, including "struct" keyword. 103 * @NAME: Name for a variable to define. 104 * @FAM: The flexible-array member within @TYPE 105 * @MEMBERS: Trailing overlapping members. 106 */ 107 #define TRAILING_OVERLAP(TYPE, NAME, FAM, MEMBERS) \ 108 union { \ 109 TYPE NAME; \ 110 struct { \ 111 unsigned char __offset_to_##FAM[offsetof(TYPE, FAM)]; \ 112 MEMBERS \ 113 }; \ 114 } 115 116 #endif 117