C语言笔记（结构体与offsetof、container_of之前的关系）

 1 typedef struct mystruct
 2 {
 3     int a;
 4     char b;
 5     double c;
 6 }MyS1;
 7 
 8 /*
 9     函数功能：演示结构体的定义和使用
10 */
11 void func1(void)
12 {
13     //定义时赋值
14     MyS1 s1 = {
15         .a =1,
16         .b =2,
17         .c = 1.23,
18     };
19     printf("s1.a = %d.\n", s1.a);
20     printf("s1.b = %d.\n", s1.b);
21     printf("s1.c = %f.\n", s1.c);
22     printf("value is change.\n");
23     // 使用.访问方式赋值
24     s1.a = 123;
25     s1.b = 4;
26     s1.c = 3.12;
27     
28     printf("s1.a = %d.\n", s1.a);
29     printf("s1.b = %d.\n", s1.b);
30     printf("s1.c = %f.\n", s1.c);
31 }

 1 typedef struct mystruct
 2 {
 3     int a;
 4     char b;
 5     double c;
 6 }MyS1;
 7 /*
 8     函数功能：演示结构体指针的使用
 9 */
10 void func2(MyS1 *s_temp)
11 {
12     s_temp->a = 12;
13     s_temp->b = 34;
14     s_temp->c = 56.123;
15     printf("s_temp->a = %d.\n", s_temp->a);
16     printf("s_temp->a = %d.\n", s_temp->b);
17     printf("s_temp->a = %f.\n", s_temp->c);
18 }
19 int main(void)
20 {
21     MyS1 s1;
22     MyS1 *ps1 = &s1;
23     func2(ps1);
24     return 0;
25 }

1 #define offsetof(TYPE, MEMBER)  ((int) &((TYPE *)0)->MEMBER)
2 
3 struct mystruct
4 {
5     int a;
6     char b;
7     double c;
8 };
9 int adr_a = offsetof(struct mystruct, b); // adr_a = 4

 1 #define container_of(ptr, type, member) ({   2    const typeof(((type *)0)->member) * __mptr = (ptr);  3    (type *)((char *)__mptr - offsetof(type, member));})
 4 
 5 typedef struct mystruct
 6 {
 7     int a;
 8     char b;
 9     double c;
10 }MyS1;
11 struct mystruct s1;
12 MyS1 *ps = NULL;
13 double *p = &s1.c;
14 printf("&s1 = %p.\n" ,&s1);
15 
16 ps = container_of(p, MyS1, c);
17 printf("ps  = %p.\n" ,ps);