向结构成员添加值时出现结构分段错误

Question

I'm getting a segmentation fault at new_session->sid = sid; . Can't figure out why.

pseudo sessions_list.h

typedef char *user;

typedef int sessionid;

struct session_list {
    sessionid sid;
    user user;
    struct session_list *next;
};
typedef struct session_list *session;

session insert_session(session, sessionid, user);
session search_session(session, sessionid);
session delete_session(session, sessionid);
void show_session_list(session);

Pseudo .c to explain the problem:

session sessions;

main(){

get_session_1_svc("this user");

}

extern  sessionid * get_session_1_svc(user * usr){
    static sessionid sid = 0;
    sid = clock();
    insert_session(sessions,sid,*usr);

    return &sid;
}

session insert_session(session session_list,sessionid sid, user user){
    session new_session = (session) (sizeof(struct session_list));
    new_session->sid = sid;
    new_session->user = user;
    new_session->next = session_list->next;
    session_list->next = new_session;
    return new_session;
}

Answer 1

Well, no wonder you are. This line:

session new_session = (session) (sizeof(struct session_list));

Is completely invalid. The fact that you are forcibly casting to session hides the error, but you are basically assigning an arbitrary number to a pointer.

I suspect that you actually want to allocate memory . In such case, you would do the following:

session new_session = malloc(sizeof(struct session_list));