Question

请告诉我我的代码有什么问题：

#include "stdio.h"

struct rights_on_cmd{
        char *gtm_cmd; /*set ,zrite ,kill...*/
        char value; /*y or n*/
} ;
struct usr_rights{
        char *username;/*user name*/
        struct rights_on_cmd rights[]; /*list gtm command & right on this command for user*/
};
struct rights_on_gbl{
        char *gbl_name;
        struct usr_rights user_list[]; /*list users have and specific right on global*/
};

int main(){
        int i ;
        struct rights_on_gbl gbl_list[2];
        for(i = 0;i <= 2; i = i + 1){
                struct rights_on_gbl gbl;
                char gbl_name[20];
                printf("Input global variable name: ");
                scanf("%s",&gbl_name);
                int j;

                gbl.gbl_name = gbl_name;
                printf("******Setting for global : %s\n",gbl_name);
                for(j = 0;j <= 2 ; j = j + 1) {

                        char username[20];
                        struct usr_rights user;
                        char *set,kill,zwrite;
                        struct rights_on_cmd set_cmd ,kill_cmd,zwrite_cmd;

                        printf("Input username: ");
                        scanf("%s",&username);                         
                        printf("Does user %s have permission on set: [y/n] ",username);
                        scanf("%s",&set);
                        set_cmd.gtm_cmd = "set";
                        set_cmd.value = set;
                        user.rights[0] = set_cmd;
                        printf("Does user %s have permission on kill: [y/n] ",username);
                        scanf("%s",&kill);
                        kill_cmd.gtm_cmd = "kill";
                        kill_cmd.value = kill;
                        user.rights[1] = kill_cmd;
                        printf("Does user %s have permission on zwrite: [y/n] ",username);
                        scanf("%s",&zwrite);
                        zwrite_cmd.gtm_cmd = "zwrite";
                        zwrite_cmd.value = zwrite;
                        user.rights[2] = zwrite_cmd;
                        user.username = username;      
                        gbl.user_list[j] = user;

                };
                gbl_list[i] = gbl;

        };
        int f ;

        for(f = 0; f < 2 ; f++){
                printf("%s",gbl_list[f].gbl_name);
        }
        return 0;
}

它在以下位置获得不定式循环：

for(j = 0;j <= 2 ; j = j + 1) { 
   ....
}

我无法找到每个循环后j索引不会增加的原因

谢谢，

//更新：此评论仅用于绕过添加代码而不是评论

Answer 1

问题：

所有这些

scanf("%s",&gbl_name);
scanf("%s",&username);  
scanf("%s",&set);
scanf("%s",&kill);
scanf("%s",&zwrite);

应该是

scanf("%s", gbl_name);
scanf("%s", username);  
scanf(" %c", &set);
scanf(" %c", &kill);
scanf(" %c", &zwrite); /* The reason for using %c is explaned below */

因为%s中的scanf需要char*，而不是char(*)[20]或char**。

你有
```
char *set,kill,zwrite;
```
宣布char* set和两个char s kill和zwrite。它应该像
```
char set, kill, zwrite;
```
因为你想输入字符而不是字符串。这就是问题＃1中最后三个scanf使用%c的原因。

Answer 2

您正在访问未初始化的数组rights []和user_list []; 使用malloc为它们分配内存，或定义边界。为考试：

struct usr_rights{
    char *username;/*user name*/
    struct rights_on_cmd rights[3]; /* << HERE */
};
struct rights_on_gbl{
    char *gbl_name;
    struct usr_rights user_list[3]; /* << and HERE*/
};

Answer 3

你的部分代码中有缓冲区溢出，你编程的行为是不可预测的。

检查这些

的界限

user.rights[0] = set_cmd;
user.rights[1] = kill_cmd;
user.rights[2] = zwrite_cmd;
gbl.user_list[j] = user;

C - 使用for循环时的不定式循环

3 个答案: