我正在使用套接字和线程开发一个客户机-服务器程序。我有一个客户机的菜单,我试图从客户机向服务器发送一个char,然后调用相应的函数。我试图利用指针和malloc,但我不太理解如何传递和释放它们。我有内存泄漏和错误,比如:
./server':双空闲或损坏(fasttop):0x00007f37dc000a50***

分段故障
这是我的客户菜单:

char *choice = (char*) malloc(sizeof(char));

do {

    // get a string from the server
    get_msg(sockfd);

    printf("\nFile and Information System\n");
    printf("===========================\n");
    printf("1. Show IP and Student ID\n");
    printf("2. Display server time\n");
    printf("3. Display system information\n");
    printf("4. List files on server\n");
    printf("5. File Transfer\n");
    printf("6. Exit\n");
    printf("Enter choice: ");
    scanf("%s", choice);

    //Send input to server
    send_menu_choice(sockfd, choice);

    switch (*choice)
    {
        case '1':
                get_ip(sockfd);
            break;
        case '2':
                get_time(sockfd);
            break;
        case '3':
                get_and_send_uname(sockfd);
            break;
        case '4':
                get_file_list(sockfd);
            break;
        case '5':
                printf("File transfer not yet implemented\n");;
            break;
        case '6':
                printf("Exiting...\n");
            break;
        default:
                printf("Invalid choice\n");
    }

    //if(menu_choice != NULL)
    //{
    //    free(menu_choice);
    //}

} while (*choice != '6');

if (choice != NULL)
{
    free(choice);
}

将菜单选项发送到服务器:
void send_menu_choice(int socketNumber, char *choice)
{
    printf("Sending menu choice...\n");
    size_t n = strlen(choice) + 1;

    writen(socketNumber, (unsigned char *) &n, sizeof(size_t));
    writen(socketNumber, (unsigned char *) choice, n);

    printf("Sent choice: %s\n\n", choice);
}

服务器端:
char *menu_choice = (char*) malloc(sizeof(char));

do {

    printf("Waiting for client to select option...\n\n");
    send_msg(connfd);

    get_menu_choice(connfd, menu_choice);
    printf("Client %d choice was: %s\n", connfd, menu_choice);

    switch (*menu_choice)
    {
        case '1':
                send_ip(connfd);
            break;
        case '2':
                send_time(connfd);
            break;
        case '3':
                get_and_send_uname(connfd, *uts);
            break;
        case '4':
                send_file_list(connfd);
            break;
        case '5':
                printf("File Transfer not implemented\n");
            break;
        case '6':
            break;
        default:
                printf("Invalid choice\n");
    }

    //if(menu_choice != NULL)
    //{
    //    free(menu_choice);
    //}

} while (*menu_choice != '6');

if (choice != NULL)
{
    free(choice);
}

从客户端获取菜单选项:
void get_menu_choice(int socketNumber, char *choice)
{
    size_t n;

    readn(socketNumber, (unsigned char *) &n, sizeof(size_t));
    readn(socketNumber, (unsigned char *) choice, n);

    printf("Received: %zu bytes\n\n", n);
}

要求的其他功能:
发送消息(服务器端):
void send_msg(int socket)
{
    char msg_string[] = "\nPlease enter an option:";

    size_t n = strlen(msg_string) + 1;
    writen(socket, (unsigned char *) &n, sizeof(size_t));
    writen(socket, (unsigned char *) msg_string, n);
}

获取消息(客户端:
void get_msg(int socket)
{
    char msg_string[32];
    size_t k;

    readn(socket, (unsigned char *) &k, sizeof(size_t));
    readn(socket, (unsigned char *) msg_string, k);

    printf("%s\n", msg_string);
}

我在这里做错什么了?我不影响指针指向的值吗?

最佳答案

do循环中,您反复释放指针

if(menu_choice != NULL)
{
    free(menu_choice);
}

但是在循环之前只分配一次。

关于c - C:如何将malloc的指针传递给函数并释放它们?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/47746112/

10-11 22:53
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