uapi/linux/stddef.h

0001 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
0002 #ifndef _UAPI_LINUX_STDDEF_H
0003 #define _UAPI_LINUX_STDDEF_H
0004
0005 #include <linux/compiler_types.h>
0006
0007 #ifndef __always_inline
0008 #define __always_inline inline
0009 #endif
0010
0011 /**
0012  * __struct_group() - Create a mirrored named and anonyomous struct
0013  *
0014  * @TAG: The tag name for the named sub-struct (usually empty)
0015  * @NAME: The identifier name of the mirrored sub-struct
0016  * @ATTRS: Any struct attributes (usually empty)
0017  * @MEMBERS: The member declarations for the mirrored structs
0018  *
0019  * Used to create an anonymous union of two structs with identical layout
0020  * and size: one anonymous and one named. The former's members can be used
0021  * normally without sub-struct naming, and the latter can be used to
0022  * reason about the start, end, and size of the group of struct members.
0023  * The named struct can also be explicitly tagged for layer reuse, as well
0024  * as both having struct attributes appended.
0025  */
0026 #define __struct_group(TAG, NAME, ATTRS, MEMBERS...) \
0027     union { \
0028         struct { MEMBERS } ATTRS; \
0029         struct TAG { MEMBERS } ATTRS NAME; \
0030     }
0031
0032 /**
0033  * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
0034  *
0035  * @TYPE: The type of each flexible array element
0036  * @NAME: The name of the flexible array member
0037  *
0038  * In order to have a flexible array member in a union or alone in a
0039  * struct, it needs to be wrapped in an anonymous struct with at least 1
0040  * named member, but that member can be empty.
0041  */
0042 #define __DECLARE_FLEX_ARRAY(TYPE, NAME)    \
0043     struct { \
0044         struct { } __empty_ ## NAME; \
0045         TYPE NAME[]; \
0046     }
0047 #endif