include/linux/stddef.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #ifndef _LINUX_STDDEF_H
0003 #define _LINUX_STDDEF_H
0004
0005 #include <uapi/linux/stddef.h>
0006
0007 #undef NULL
0008 #define NULL ((void *)0)
0009
0010 enum {
0011     false   = 0,
0012     true    = 1
0013 };
0014
0015 #undef offsetof
0016 #define offsetof(TYPE, MEMBER)  __builtin_offsetof(TYPE, MEMBER)
0017
0018 /**
0019  * sizeof_field() - Report the size of a struct field in bytes
0020  *
0021  * @TYPE: The structure containing the field of interest
0022  * @MEMBER: The field to return the size of
0023  */
0024 #define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
0025
0026 /**
0027  * offsetofend() - Report the offset of a struct field within the struct
0028  *
0029  * @TYPE: The type of the structure
0030  * @MEMBER: The member within the structure to get the end offset of
0031  */
0032 #define offsetofend(TYPE, MEMBER) \
0033     (offsetof(TYPE, MEMBER) + sizeof_field(TYPE, MEMBER))
0034
0035 /**
0036  * struct_group() - Wrap a set of declarations in a mirrored struct
0037  *
0038  * @NAME: The identifier name of the mirrored sub-struct
0039  * @MEMBERS: The member declarations for the mirrored structs
0040  *
0041  * Used to create an anonymous union of two structs with identical
0042  * layout and size: one anonymous and one named. The former can be
0043  * used normally without sub-struct naming, and the latter can be
0044  * used to reason about the start, end, and size of the group of
0045  * struct members.
0046  */
0047 #define struct_group(NAME, MEMBERS...)  \
0048     __struct_group(/* no tag */, NAME, /* no attrs */, MEMBERS)
0049
0050 /**
0051  * struct_group_attr() - Create a struct_group() with trailing attributes
0052  *
0053  * @NAME: The identifier name of the mirrored sub-struct
0054  * @ATTRS: Any struct attributes to apply
0055  * @MEMBERS: The member declarations for the mirrored structs
0056  *
0057  * Used to create an anonymous union of two structs with identical
0058  * layout and size: one anonymous and one named. The former can be
0059  * used normally without sub-struct naming, and the latter can be
0060  * used to reason about the start, end, and size of the group of
0061  * struct members. Includes structure attributes argument.
0062  */
0063 #define struct_group_attr(NAME, ATTRS, MEMBERS...) \
0064     __struct_group(/* no tag */, NAME, ATTRS, MEMBERS)
0065
0066 /**
0067  * struct_group_tagged() - Create a struct_group with a reusable tag
0068  *
0069  * @TAG: The tag name for the named sub-struct
0070  * @NAME: The identifier name of the mirrored sub-struct
0071  * @MEMBERS: The member declarations for the mirrored structs
0072  *
0073  * Used to create an anonymous union of two structs with identical
0074  * layout and size: one anonymous and one named. The former can be
0075  * used normally without sub-struct naming, and the latter can be
0076  * used to reason about the start, end, and size of the group of
0077  * struct members. Includes struct tag argument for the named copy,
0078  * so the specified layout can be reused later.
0079  */
0080 #define struct_group_tagged(TAG, NAME, MEMBERS...) \
0081     __struct_group(TAG, NAME, /* no attrs */, MEMBERS)
0082
0083 /**
0084  * DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
0085  *
0086  * @TYPE: The type of each flexible array element
0087  * @NAME: The name of the flexible array member
0088  *
0089  * In order to have a flexible array member in a union or alone in a
0090  * struct, it needs to be wrapped in an anonymous struct with at least 1
0091  * named member, but that member can be empty.
0092  */
0093 #define DECLARE_FLEX_ARRAY(TYPE, NAME) \
0094     __DECLARE_FLEX_ARRAY(TYPE, NAME)
0095
0096 #endif