警告 - 预期为“struct node **"但参数类型为“struct node **"是什么意思? [英] What does the warning - expected ‘struct node **’ but argument is of type ‘struct node **’ mean?

问题描述

我从数组创建树的代码:

My code for tree creation from array:

#include<stdio.h>
#include<malloc.h>
typedef struct
{
    struct node* left;
    struct node* right;
    int val;
}node;

void create_tree(node** root,int val)
{

    if(*root == NULL )
    {
        *root = (node*)malloc(sizeof(node));
        (*root)->val = val;
        (*root)->left = NULL;
        (*root)->right = NULL;
        return;
    }   
    if((*root)->val <= val )
        create_tree(&((*root)->left),val);
    else
        create_tree(&((*root)->right),val);

    return ;    
}



int main()
{
    node *root = (node*)malloc(sizeof(node));
    root->val = 10;
    root->left = NULL;
    root->right = NULL;
    int val[] = { 11,16,6,20,19,8,14,4,0,1,15,18,3,13,9,21,5,17,2,7,12};
    int i;
    for(i=0;i<22;i++)   
        create_tree(&root,val[i]);
    return 0;
}

我收到警告:

tree.c:10:6: note: expected ‘struct node **’ but argument is of type ‘struct node **’
 void create_tree(node** root,int val)
      ^

我不明白这个警告说的是什么?预期和实际都是 struct node ** 类型.是bug吗?

I am not able to understand what does this warning say? Both expected and actual are of type struct node **. Is it a bug?

推荐答案

编辑后(这就是我们要求 [mcve] 的原因)，很清楚问题所在.

After the edit (that's why we ask for a [mcve]), it is clear what the problem is.

在您的 struct 中，您引用了一个 struct 节点.但是你没有定义那个类型，你只是为一个本身没有名字的结构定义了别名node.

Inside your struct, you reference a struct node. But you do not define that type, you only define the alias node for a struct which has no name by itself.

请注意，在 C 中，struct node 驻留在与变量或 typedefed 别名等正常"名称不同的命名空间中.

Note that in C struct node resides in a different namespace than "normal" names like variables or typedefed aliases.

所以你必须添加一个标签:

So you have to add a tag:

typedef struct node {
    struct node* left;
    struct node* right;
    int val;
} node;

这样你就有了一个 struct node 以及一个名为 node 的类型.

That way you have a struct node as well as a type with name node.

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