运行环境：VS2019(C语言编写)

问题：写入访问权限冲突（res[*resSize++] = root->val;语句引发）

/****
二叉树前序遍历实现
***/
#include<stdio.h>
#include<malloc.h>
typedef struct TreeNode {
	struct TreeNode* left;
	struct TreeNode* right;
	int val;
}BiTree;
/**
初始化树
***/
void CreateTree(TreeNode **T){
	int value = -1;
	printf("输入结点的值：\n");
	scanf_s("%d", &value);
	if (value == -1) {
		*T = NULL;
	}
	else {
		*T =(TreeNode*)malloc(sizeof(TreeNode));
		(*T)->val = value;
		CreateTree(&(*T)->left);
		CreateTree(&(*T)->right);
	}
}
void PreOrder(struct TreeNode* root,int *res,int *resSize){
	if (root == NULL) return;
	/***
	这里显示写入异常
	***/ 
	res[*resSize++] = root->val;
	PreOrder(root->left,res,resSize);
	PreOrder(root->right,res,resSize);
}
int* PreOrderTraversal(struct TreeNode* root,int *returnSize){
	int* res = (int*)malloc(sizeof(int)*2000);
	*returnSize = 0;
	PreOrder(root,res,returnSize);
	return res;
}
int main() {
	TreeNode* T;
	CreateTree(&T);
	int returnSize;
	int *head = PreOrderTraversal(T,&returnSize);
	//在树的结点值不为0的时候遍历的方式
	return 0;
}