multi inheritance with list_head.

  1. typedef struct OLNode {    
  2.      int  LineNumber, ColumneNumber;
  3.      ElemType value;
  4.      struct OLNode *right, *down;
  5. }OLNode, *OList;

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small test

  1. #include <stdio.h>
  2. #include <stddef.h>
  4. typedef struct list_head {
  5.     int count;
  6. }list_head ;
  8. int ref(struct list_head *obj) {
  9.     return obj->count;
  10. }
  13. #define CustomTransfer_T(a) ( (_customObject*) ( ((char*)a) - \
  14. offsetof(_customObject,obj_T) ) )
  16. typedef struct _customObject {
  17.     int obj;
  18.     int obj_T;
  19.     int extra;
  20. }_customObject;
  22. int sum(_customObject *obj) {
  23.     return obj->extra+ ref((list_head*)&obj->obj) + ref((list_head*)&obj->obj_T);
  24. }
  26. void main() {
  27.     _customObject custom = {10,11,12};
  29.     printf("%d\n",ref((list_head*)&custom.obj));
  30.     printf("%d\n",ref((list_head*)&custom));
  31.     printf("%d\n",ref((list_head*)(&custom.obj_T)));
  33.     list_head* parent_T = (list_head*)&custom.obj_T;
  34.     printf("%d\n",sum(CustomTransfer_T(parent_T)));
  35. }

Linux 2.4

Linux 2.4 版本中还是最初质朴的定义, 最好研究
https://elixir.bootlin.com/linux/2.4.31/source/include/linux/list.h#L187

  1. /**
  2.  * list_entry - get the struct for this entry
  3.  * @ptr:    the &struct list_head pointer.
  4.  * @type:    the type of the struct this is embedded in.
  5.  * @member:    the name of the list_struct within the struct.
  6.  */
  7. #define list_entry(ptr, type, member) \
  8.     ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))

Linux 5.9

Linux 5.9 版本中 从 list 寻找 structure 的函数定义转移到了 /include/linux/kernel
https://elixir.bootlin.com/linux/v5.9-rc8/source/include/linux/kernel.h#L1000

  1. /**
  2.  * container_of - cast a member of a structure out to the containing structure
  3.  * @ptr:    the pointer to the member.
  4.  * @type:    the type of the container struct this is embedded in.
  5.  * @member:    the name of the member within the struct.
  6.  *
  7.  */
  8. #define container_of(ptr, type, member) ({                \
  9.     void *__mptr = (void *)(ptr);                    \
  10.     BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) &&    \
  11.              !__same_type(*(ptr), void),            \
  12.              "pointer type mismatch in container_of()");    \
  13.     ((type *)(__mptr - offsetof(type, member))); })