include/uapi/linux/stddef.h

   1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
   2 #ifndef _UAPI_LINUX_STDDEF_H
   3 #define _UAPI_LINUX_STDDEF_H
   4
   5 #include <linux/compiler_types.h>
   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 #ifdef __cplusplus
  33 /* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */
  34 #define __DECLARE_FLEX_ARRAY(T, member) \
  35         T member[0]
  36 #else
  37 /**
  38  * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
  39  *
  40  * @TYPE: The type of each flexible array element
  41  * @NAME: The name of the flexible array member
  42  *
  43  * In order to have a flexible array member in a union or alone in a
  44  * struct, it needs to be wrapped in an anonymous struct with at least 1
  45  * named member, but that member can be empty.
  46  */
  47 #define __DECLARE_FLEX_ARRAY(TYPE, NAME)        \
  48         struct { \
  49                 struct { } __empty_ ## NAME; \
  50                 TYPE NAME[]; \
  51         }
  52 #endif
  53
  54 #ifndef __counted_by
  55 #define __counted_by(m)
  56 #endif
  57
  58 #endif /* _UAPI_LINUX_STDDEF_H */