错误：取消引用指向不完整类型的指针 [英] ERROR: dereferencing pointer to incomplete type

问题描述

//下面的代码行给出了上面提到的错误

// printf（％d，root-> left-> info）;

//算法或编码是否有任何缺陷

//The following line of code gives above mentioned error
//printf("%d",root->left->info);
// is there any flaw in the algorithm or coding

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>


typedef struct Node
{
    int info;
    struct node* left;
    struct node* right;
}node;

void insert(node *root,int item)
{
    node *parent,*cur;
    parent=NULL;
    cur=root;
    while(cur!=NULL)
    {
        parent=cur;
        if(item<=cur->info)
        cur=cur->left;
        else
        cur=cur->right;
    }
    if(parent==NULL)
    {
        root->info=item;
        root->left=NULL;
        root->right=NULL;
    }
    else if(item<parent->info)
    {
        node *newNode=(int*)malloc(sizeof(node));
        newNode->info=item;
        newNode->left=NULL;
        newNode->right=NULL;
        parent->left=newNode;
    }
    else
    {
        node *newNode=(int*)malloc(sizeof(node));
        newNode->info=item;
        newNode->left=NULL;
        newNode->right=NULL;
        parent->right=newNode;
    }
}


int main()
{
    node *root=(node*)malloc(sizeof(node));
    root->info=6;
    root->left=NULL;
    root->right=NULL;
    insert(root,4);
    printf("%d",root->left->info);
    getch();
}

推荐答案

问题在于节点结构的定义：

The problem lies in the definition of your node structure:

typedef struct Node
{
    int info;
    struct node* left;    // <----
    struct node* right;   // <----
}node;

没有struct node，只有struct Node（大写）。因此左指向尚未定义的结构的指针，编译器很乐意接受，直到您尝试取消引用它。所以将左边定义为struct Node *，一切都会好的。



顺便说一句。你不能将 left 定义为node *，因为此时尚未定义node。

There is no "struct node", but only a "struct Node" (uppercase). And hence is left a pointer to a yet undefined structure, which the compiler gladly accepts until you try to dereference it. So define left as "struct Node*" and everything will be fine.

Btw. you cannot define left as "node*" because the "node" has not yet been defined at that point.

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