c语言 - 警告：从'mode_t'(也称为"无符号 int *")分配给'node_t *'(也称为"结构节点 *")的不兼容指针类型

Question

我们的项目是关于使用机器人和我们学院的一位教授开发的软件来创建电影。该库称为MyroC，机器人利用该库实现许多功能。理想情况下，我们让机器人拍摄用户输入的若干帧(图片(。用户还可以选择在主电影中插入"场景"或小子电影。

我是一名学习C语言的初级程序员。在我最近的学校项目中，我和我的搭档在处理 C 语言中的指针和链接列表时遇到了很多麻烦。我们理解为列表中的节点赋值和更改地址的基本思想，但我们似乎无法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，我们没有看到我们可能做错了什么。

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

端子输出

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揭示了所有信息。您在声明之前正在使用node_t，您可以在它下面使用它。

事物在使用之前需要声明/定义。

所以移动...

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

所以它变成了...

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;
};