警告：不兼容的指针类型从“ mode_t”（又称为“ unsigned int *”）分配给“ node_t *”（也称为“结构节点*”）

Question

我们的项目是关于使用我们学院一位教授开发的机器人和软件制作电影。该库称为MyroC，机器人将这个库用于许多功能。理想情况下，我们让机器人拍摄用户输入的许多帧（图片）。用户还可以选择在主电影中插入“场景”或少量子电影。

我是学习C语言的初学者。在我最近的学校项目中，我和我的搭档在使用C语言中的指针和链接列表时遇到了很多麻烦。我们了解为列表中的节点分配值和更改地址的基本思想，但是我们做不到似乎弄清楚了我们的警告来自何处。我们搜索了各种在线资源和文本，以比较我们的代码语法，但看不到哪里可能做错任何事情。

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

您的第一个错误消息显示所有内容。在声明它之前，您正在使用node_t，该操作在它下面进行。

事物在使用前需要声明/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;
};