线程处理程序上的分段错误

时间:2019-02-11 19:04:00

标签: c segmentation-fault pthreads chatbot

我的Chatbot轮询功能无法正常工作, 我在线程处理程序上遇到分段错误,我使用gdb查看更多内容,这就是我得到的:

Thread 4 "St3veB0t" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff67c2700 (LWP 5957)]
0x0000555555557243 in poll_handler ()
(gdb) bt
#0  0x0000555555557243 in poll_handler ()
#1  0x00007ffff7bbd6db in start_thread (arg=0x7ffff67c2700)
    at pthread_create.c:463
#2  0x00007ffff78e688f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

函数poll_handler()是这样的:

void * poll_handler(void * args)
{
    FILE * fp;
    struct VoteData  vote;
    struct PollHandlerData * data = (struct PollHandlerData *)args;
    int res;
    char * string = (char *)malloc(sizeof(char)*MAX_BUFFER);


    sleep(60);
    *data->status = 0;    
    *data->vote_count = 0;

    if(!(fp = fopen("polls/votes.txt", "r")))
    {
        fprintf(stderr, "\nError in reading file\n");
         if(!(fp = fopen("polls/votes.txt", "w+")))
         {
            fprintf(stderr, "\nError in creating file\n");
            exit(EXIT_FAILURE);
         }
    }

    vote = GetMostVote(fp);

    strcpy(string, "PRIVMSG #st3ver0nix : Polling terminated, the majority voted: ");
    strcat(string, vote.word);
    strcat(string, "\r\n");

     do{
        res = write(data->sock, string, strlen(string));
    }while(res < strlen(string));

    fclose(fp);
    free(string);
    pthread_exit(NULL);
}

创建线程的函数是这样的:

void CreatePoll(int sock, char * message, char * poll_name, int * status, int * vote_count)
{
    pthread_t tid;
    struct PollHandlerData * data = (struct PollHandlerData *)malloc(sizeof(struct PollHandlerData));
    char * name = (char *)malloc(sizeof(char)*MAX_BUFFER);


    GetPollName(message, name);
    sscanf(name, "%s", poll_name);

    data->sock = sock;
    data->status = status;
    sscanf(poll_name, "%s", data->name);

    pthread_create(&tid, NULL, poll_handler, (void *)data);
    pthread_detach(tid);

    free(name);
}

结构PollHandlerDataVoteData具有以下形式:

struct PollHandlerData
{
    int sock;
    char name[128];
    int * status;
    int * vote_count;
};

struct VoteData
{
    char word[128];
    int freq;
};

我真的不知道我的代码有什么问题。我正在使用POSIX pthreads。 请让我知道您是否需要有关代码的更多信息。

1 个答案:

答案 0 :(得分:1)

根据poll_handler()线程分配中的观察,vote_count导致此崩溃:

*data->vote_count = 0;

在函数CreatePoll()中创建变量vote_count内的线程data之前,指针未分配或未指向任何有效的指针,因为仅对变量data执行了malloc它将具有任何垃圾值。因此,在访问无效指针时,它在poll_handler()中崩溃了。

注意:vote_count将具有垃圾值,如果这是该进程的有效指针,则可能不会使进程崩溃。