tools/include/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 #ifndef __always_inline
   6 #define __always_inline inline
   7 #endif
   8
   9 /**
  10  * __struct_group() - Create a mirrored named and anonyomous struct
  11  *
  12  * @TAG: The tag name for the named sub-struct (usually empty)
  13  * @NAME: The identifier name of the mirrored sub-struct
  14  * @ATTRS: Any struct attributes (usually empty)
  15  * @MEMBERS: The member declarations for the mirrored structs
  16  *
  17  * Used to create an anonymous union of two structs with identical layout
  18  * and size: one anonymous and one named. The former's members can be used
  19  * normally without sub-struct naming, and the latter can be used to
  20  * reason about the start, end, and size of the group of struct members.
  21  * The named struct can also be explicitly tagged for layer reuse, as well
  22  * as both having struct attributes appended.
  23  */
  24 #define __struct_group(TAG, NAME, ATTRS, MEMBERS...) \
  25         union { \
  26                 struct { MEMBERS } ATTRS; \
  27                 struct TAG { MEMBERS } ATTRS NAME; \
  28         } ATTRS
  29
  30 #ifdef __cplusplus
  31 /* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */
  32 #define __DECLARE_FLEX_ARRAY(T, member) \
  33         T member[0]
  34 #else
  35 /**
  36  * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
  37  *
  38  * @TYPE: The type of each flexible array element
  39  * @NAME: The name of the flexible array member
  40  *
  41  * In order to have a flexible array member in a union or alone in a
  42  * struct, it needs to be wrapped in an anonymous struct with at least 1
  43  * named member, but that member can be empty.
  44  */
  45 #define __DECLARE_FLEX_ARRAY(TYPE, NAME)        \
  46         struct { \
  47                 struct { } __empty_ ## NAME; \
  48                 TYPE NAME[]; \
  49         }
  50 #endif
  51
  52 #ifndef __counted_by
  53 #define __counted_by(m)
  54 #endif
  55
  56 #endif /* _UAPI_LINUX_STDDEF_H */