Linux 内核宏 container_of

1.定义

 container_of(ptr, type, member);

ARGUMENTS
       ptr
           the pointer to the member.//代表指针
       type
           the type of the container struct this is embedded in.//类型

       member　//成员变量
           the name of the member within the struct.

作用:通过一个结构体变量中的成员地址找到这个结构体变量的首地址

２.例子

#include <stdio.h>


#undef offsetof
#ifdef __compiler_offsetof
#define offsetof(TYPE, MEMBER)  __compiler_offsetof(TYPE, MEMBER)
#else
#define offsetof(TYPE, MEMBER)  ((size_t)&((TYPE *)0)->MEMBER)
#endif

#define container_of(ptr, type, member) ({                  \
                            const typeof( ((type*)0)->member ) *__mptr = (ptr); \
                            (type*)( (char*)__mptr - offsetof(type,member) ); })

typedef struct {
    int age;
    int num;
} student;

int main(){
    student s;
    printf("ss:%p\n", &s);

    student *temp = container_of(&s.num, student, num);

    printf("temp:%p\n", temp);

    return 0;
}

结果:
ss:0x7fff156fe320
temp:0x7fff156fe320
通过s.num的地址找到了结构体变量的地址