警告：从'mode_t'（又名'unsigned int *'）分配给'node_t *'（又名'struct node *'）的指针类型不兼容

Question

我们的项目是关于使用由我们学院的一位教授开发的机器人和软件制作电影。该库名为MyroC，机器人将此库用于许多功能。理想情况下，我们让机器人拍摄用户输入的多个帧（图片）。用户还可以选择将“场景”或小的子电影插入主电影中。

我是一名初学者，正在学习C语言。在我最近的学校项目中，我和我的合作伙伴在使用C中的指针和链接列表时遇到了很多麻烦。我们理解将值分配给列表中的节点和更改地址的基本思路，但我们不能似乎弄清楚我们的警告来自哪里。我们搜索了各种在线资源和文本来比较我们的代码语法，但我们没有看到我们在哪里做错了什么。

这是我们的代码：

//This part is contained in a separate header file called "movie.h"

    struct node { /* Singly-linked list nodes contain a Picture and point to next */
      Picture frame;
      node_t * next;
    };

    typedef struct node node_t;   /* Shorthand type for nodes in the picture list */

    typedef struct {     /* Wrapper struct for the movie as a linked list */
      node_t * first;
      node_t * last;
    } movie_t;

// This part is contained in a separate file called "movie.c" 
// An appropriate reference is made to movie.h
// #include "movie.h"

    movie_t
    create (void)
    {
      movie_t movie = {NULL, NULL}; // initially create an empty movie
      return movie;
    } // movie

    size_t
    size (movie_t * movie)
    {
      unsigned int count = 0;
      node_t * current = movie->first;
      while (current != NULL) {
        count++;
        current = current->next;
      }
        return count;
    } // size

    bool
    is_empty (movie_t * movie)
    {
      if (size(movie)==0) // movie contains no frames
        return true;
      else
        return false; // movie contains frames
    } // empty


    bool
    add (movie_t * movie, Picture frame) // add a frame to the end of the movie
    {
      int before_size = size(movie);

      node_t * new_node;
      new_node = malloc(sizeof(node_t));

      if (new_node == NULL) {
        printf("Error, malloc failed.\n");
        exit(EXIT_FAILURE);
      }

      node_t * cursor = movie->first;
      while(cursor->next != NULL) {
        cursor=cursor->next;
      }
      cursor->next = new_node;
      movie->last = new_node;
      new_node->frame = frame;

      if (before_size < size(movie) && (is_empty(movie)==false))
        return true;
      else
        return false;
    } // add


    void // insert a frame before index
    insert (movie_t * movie, movie_t * scene, unsigned int index)
    {
      node_t *insertion;
      insertion = malloc(sizeof(node_t));
      if (insertion == NULL) {
        printf("Error, malloc failed.\n");
        exit(EXIT_FAILURE);
      }

      insertion = movie->first;

      for (unsigned int i = 0; i < index; i++) {
        if (insertion != NULL) 
          insertion = insertion->next;
      }
      scene->last = insertion->next;
      insertion->next = scene->first;

    } // insert

终端输出

error: unknown type name 'node_t'; did you mean 'mode_t'?
node_t * next;
^~~~~~
mode_t   
/usr/include/x86_64-linux-gnu/sys/types.h:70:18: note: 'mode_t' declared here    

Answer 1

您的第一条错误消息显示全部。您在声明它之前使用node_t，而在它下面执行它。

在使用之前需要声明/定义事物。

所以搬家......

typedef struct node node_t;   /* Shorthand type for nodes in the picture list */

所以它变成......

typedef struct node node_t;   /* Shorthand type for nodes in the picture list */

//This part is contained in the header file "movie.h"
struct node { /* Singly-linked list nodes contain a Picture and point to next */
   Picture frame;
    node_t * next;
};