宏container_of用法问题

hubimaso

1. #include <stdio.h>
   
2. 
   
3. #define FIND(TYPE,MEMBER) (size_t)&(((TYPE*)0)->MEMBER)
   
4. 
   
5. #define container_of(ptr, type, member) ({                      \
   
6.         const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
   
7.         (type *)( (char *)__mptr - offsetof(type,member) );})
   
8. 
   
9. struct list_head {
   
10.         struct list_head *next, *prev;
    
11. };
    
12. 
    
13. struct student
    
14. {
    
15.         int a;
    
16.         char b[19];
    
17.         double c;
    
18.         struct list_head list;
    
19. };
    
20. 
    
21. int main(void)
    
22. {       
    
23.         struct student s= {1,{0},0.0,{NULL,NULL}};
    
24.         struct list_head * ptr = &s.list;
    
25. 
    
26.         printf("%08x\n",s);
    
27.         printf("%08x\n",&s);
    
28.         printf("%08x\n",&s.a);
    
29.         printf("%08x\n",&s.b);
    
30.         printf("%08x\n",&s.c);
    
31.         printf("%08x\n",FIND(struct student,c));
    
32.         struct student *stu  = container_of(ptr,struct student,s.list);//这一句上有问题。
    
33.         printf("%08x\n",stu);
    
34.         return 0;
    
35. }

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hk2305621

1. #include <stdio.h>
   
2. 
   
3. #define FIND(TYPE,MEMBER) (size_t)&(((TYPE*)0)->MEMBER)
   
4. 
   
5. #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
   
6. 
   
7. #define container_of(ptr, type, member) ({                      \
   
8.         const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
   
9.         (type *)( (char *)__mptr - offsetof(type,member) );})
   
10. 
    
11. struct list_head {
    
12.     struct list_head *next, *prev;
    
13. };
    
14. 
    
15. struct student
    
16. {
    
17.     int a;
    
18.     char b[19];
    
19.     double c;
    
20.     struct list_head list;
    
21. };
    
22. 
    
23. int main(void)
    
24. {        
    
25.     struct student s= {1,{0},0.0,{NULL,NULL}};
    
26.     struct list_head * ptr = &s.list;
    
27. 
    
28.     printf("%08x\n",s);
    
29.     printf("%08x\n",&s);
    
30.     printf("%08x\n",&s.a);
    
31.     printf("%08x\n",&s.b);
    
32.     printf("%08x\n",&s.c);
    
33.     printf("%08x\n",FIND(struct student,c));
    
34.     struct student *stu  = container_of(ptr,struct student, list);//这一句上有问题。
    
35.     printf("%08x\n",stu->a);
    
36.     return 0;
    
37. }

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你忘记声明 container_of 中的 offsetof 宏了.

而且在使用 container_of 的时候, 也有错误. 第三个参数, 是对象在结构体中的名称.

hubimaso

你试了没呀，我在vc6上试还是编译不通回复 2# hk2305621


   

hk2305621

我在 linux 下用 gcc 编译的.  是 ok 的.

VC 6 好像有自己的 offset 函数.

1. $ gcc container.c
   
2. container.c: In function ‘main’:
   
3. container.c:28: warning: format ‘%08x’ expects type ‘unsigned int’, but argument 2 has type ‘struct student’
   
4. container.c:29: warning: format ‘%08x’ expects type ‘unsigned int’, but argument 2 has type ‘struct student *’
   
5. container.c:30: warning: format ‘%08x’ expects type ‘unsigned int’, but argument 2 has type ‘int *’
   
6. container.c:31: warning: format ‘%08x’ expects type ‘unsigned int’, but argument 2 has type ‘char (*)[19]’
   
7. container.c:32: warning: format ‘%08x’ expects type ‘unsigned int’, but argument 2 has type ‘double *’
   
8. $ ./a.out
   
9. 00000001
   
10. bfc2b6e4
    
11. bfc2b6e4
    
12. bfc2b6e8
    
13. bfc2b6fc
    
14. 00000018
    
15. 00000001

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hubimaso

非常感谢！！！终于等到了。呵呵，能加个qq吗？我qq：718268255.回复 4# hk2305621


   

hk2305621

回头找你. 在公司, 不能上Q. 我的Q. 394831530.

hantown

楼主高手，把Linux程序移植到windows

allen303allen

楼主问题解决了咋不来公布下结果呢？
linux的链表确实是个不错的设计，把它移植到windows应该很多人都干过吧，我以前也做过。
VC6确实有自己的offsetof，我在VC下的container_of是这么写的：

1. #define container_of(ptr, type, member)                \
   
2.         (type *)((char *)ptr - offsetof(type, member))

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