c - 从不完整的指针类型分配

大家晚上好。
我现在遇到了一个奇怪的警告，我一辈子都搞不清哪里出了问题。我试过很多不同的选择，我记不起来了。
错误是：
来自不兼容指针类型的赋值
相关代码：

// Server structure
typedef struct {
    struct addrinfo address;        // Address info
    char buffer[1024];              // Read biffer
    fd_set connections;             // Current connections
    int connections_max;            // Max file descriptor
    int listener;                   // Listener fd
    int port;                       // The port for the server to listen on
    struct addrinfo socket_hints;   // Server's socket hints
    struct timeval socket_timeout;  // When should the socket timeout?
    struct User *users;             // Currently connected users
} Server;

// User structure
typedef struct {
    struct sockaddr_storage address;    // User's address
    socklen_t address_length;           // Length of users address
    int fs_id;                          // ID to the socket they belong to
    char ip_address[INET6_ADDRSTRLEN];  // User's IP address
    char *name;                         // Pointer to the user's name
    struct User *nextUser;              // Next user in the list
} User;

/**
 * Handles sockets on the provided server
 */
void handle_sockets(Server *passed_server) {
    int current_fd;             // Current file descriptor
    int new_connection;         // Socket ID of new connections
    fd_set read_sockets;        // Sockets to read from
    FD_ZERO(&read_sockets);
    struct timeval timeout;     // Sets the timeout for select

    // See if we have sockets to read
    read_sockets = passed_server->connections;
    timeout = passed_server->socket_timeout;
    if(select(passed_server->connections_max+1, &read_sockets, NULL, NULL, &timeout) == -1) {
        perror("Selecting sockets");
        exit(1);
    }

    // Loop through all of the sockets
    for(current_fd = 0; current_fd <= passed_server->connections_max; current_fd++) {
        if(!FD_ISSET(current_fd, &read_sockets)) {
            continue;
        }

        // Handle new connection
        if(current_fd == passed_server->listener) {
            User *new_user = malloc(sizeof *new_user);
            memset(&new_user->address, 0, sizeof new_user->address);

            // Get the new address
            new_user->address_length = sizeof new_user->address;
            new_user->fs_id = accept(passed_server->listener, (struct sockaddr *)&new_user->address, &new_user->address_length);

            // Did we have an issue connecting?
            if(new_user->fs_id == -1) {
                free(new_user);
                perror("Accepting new connection");
                continue;
            }

            // Add the user socket to the master list
            FD_SET(new_user->fs_id, &passed_server->connections);
            if(new_user->fs_id > passed_server->connections_max) {
                passed_server->connections_max = new_user->fs_id;
            }

            // Add the user to the list

            //*******************
            // ERRORS IN THE NEXT TWO ASSIGNMENTS
            //*******************

            if(passed_server->users == NULL) {
                passed_server->users = new_user;
            } else {
                new_user->nextUser = passed_server->users;
                passed_server->users = new_user;
            }

            // Let them know we got one!
            printf("Server: New connection from %s on socket %d. Send hello.\n",
                    inet_ntop(
                            new_user->address.ss_family,
                            get_address((struct sockaddr*)&new_user->address),
                            new_user->ip_address,
                            INET6_ADDRSTRLEN
                    ),
                    new_user->fs_id
            );

            // Can we get to the user from the server?
            //printf("Repeat, the IP address is %s\n", passed_server->users->ip_address);

            // Move on to the next file descriptor
            continue;
        }
    }
}

Full Code

最佳答案

typedef struct User {
    struct sockaddr_storage address;    // User's address
    socklen_t address_length;           // Length of users address
    int fs_id;                          // ID to the socket they belong to
    char ip_address[INET6_ADDRSTRLEN];  // User's IP address
    char *name;                         // Pointer to the user's name
    struct User *nextUser;              // Next user in the list
} User;

在顶部添加“struct User”，以便可以在结构中引用它。
此外，还需要交换声明的顺序，以便服务器结构知道用户结构。