使用数组创建单链接列表时出现警告

Question

#include <stdio.h>

typedef struct
{
  int data;
  struct node *next;
}node;

void print(node *head)
{
  node *tmp = head;
  while (tmp)
  {
    printf ("%d ", tmp->data);
    tmp = tmp->next;
  }
}

int main()
{
  node arr[5] = {
                  {1, &arr[1]},
                  {2, &arr[2]},
                  {3, &arr[3]},
                  {4, &arr[4]},
                  {5, NULL}
                };

  print(arr);
  return 0;
}

为什么在使用gcc -Wall编译时会收到这些警告？(即使没有-Wall,gcc会产生相同的警告)

list.c: In function ‘print’:
list.c:15:7: warning: assignment from incompatible pointer type [enabled by default]
list.c: In function ‘main’:
list.c:22:18: warning: initialization from incompatible pointer type [enabled by     default]
list.c:22:18: warning: (near initialization for ‘arr[0].next’) [enabled by default]
list.c:23:18: warning: initialization from incompatible pointer type [enabled by default]
list.c:23:18: warning: (near initialization for ‘arr[1].next’) [enabled by default]
list.c:24:18: warning: initialization from incompatible pointer type [enabled by default]
list.c:24:18: warning: (near initialization for ‘arr[2].next’) [enabled by default]
list.c:25:18: warning: initialization from incompatible pointer type [enabled by default]
list.c:25:18: warning: (near initialization for ‘arr[3].next’) [enabled by default]

Answer 1

@metalhead说的是对的.实现相同结果的另一种可能更好的方法是

typedef struct _node
{
  int data;
  struct _node *next;
} node;

在此定义之后,节点(没有下划线)可以简单地用作类型名称,例如int.

PS 的下划线是只是一个标准的惯例,而不是要求.只要您在两个匹配项中都替换,就可以使用任何名称代替_node.但是,在c中,这是一种规范和一种编码约定,可以帮助开发人员快速理解 _node 实际上指的是节点类型.