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Posted 2022-12-11 embeded-linux

offsetof和container_of宏

offsetof宏的作用：计算结构体中某个元素相对结构体首地址的偏移量

container_of宏的作用：知道结构体变量中某个成员的指针，反推这个结构体变量的指针

#include <stdio.h>
#define offsetof(type,member) ((int) &((type *)0)->member)
#define container_of(ptr,type,member) (    const typeof(((type *)0)->member) *mptr = (ptr);    (type *)((char *)mptr - offsetof(type,member));)
//typeof关键字的作用：typeof(a)由变量a获得变量a的类型
typedef struct node
    int a;
    double b;
    float c;
 n1;
int main()

    n1 s;
    float *p = &(s.c);
    printf("offsetof(c) = %d\n",offsetof(n1,c));
    printf("addr of s is %p\n",&s);
    printf("container_of(p,n1,c) = %p\n",container_of(p,n1,c));
    return 0;
    

sizeof(short) = 2
sizeof(int) = 4
sizeof(long) = 4

--------------------------------
Process exited after 0.1803 seconds with return value 0
请按任意键继续. . .

运行结果