不能将struct Node* 的值赋给struct Node *实体？这都什么情况啊

#include <iostream>
#include <stdlib.h>
#include<malloc.h>
#include <string>
#include <vector>
#include <sstream>

using namespace std;

struct userNode
{
    string  account  ;//账号
    string  password ;//密码
    char    order;//命令符，判断是登陆还是申请
};

struct hashHead
{
    int tableSize;
    struct listNode *theLists;
};

struct listNode
{
    struct userNode userMessage;
    struct listNode *next;
};
struct hashHead*  initHashTable(  int  tableSize  )
{
    tableSize = nextPrime(   tableSize ) ;

    struct hashHead* hash;
    hash = (struct  hashHead* )malloc( sizeof( struct  hashHead  ) )  ;
    hash->tableSize = tableSize ;

    hash->theLists = (struct listNode*) malloc(tableSize* sizeof( struct listNode )  )  ;

    for ( int i = 0; i < tableSize; ++i )
    {
        hash->theLists[i].next = NULL ;
        hash->theLists[i].userMessage.account = "0";//账号密码全部默认为0
        hash->theLists[i].userMessage.password = "0";
        hash->theLists[i].userMessage.order = '0';
    }
    return hash;
}

int nextPrime(  int size )
{
    int i;
    if(size % 2 == 0 ) ++size;
    for ( ; ; size += 2 )
    {
        for (i = 3; i*i < size; ++i)//判断size是否为素数
            if (size % i == 0)  break ;
        if (i*i > size)  return size ;
    }
}


void checkAndOutPut(  struct userNode *user , struct hashHead*  hash )
{
    //将账号后五位数字作为有效数字，用于计算散列址
    int address  ;
    //number = atoi( (user->account+5) ) ;
    address= atoi(  user->account.c_str()   )% hash->tableSize  ;//未截取

    struct listsNode *pos ;
    pos = find(user, hash) ;//出错了？？
    if (  pos  )//找到后核对用户信息
    {
        if (user->password == find(user, hash)->userMessage.password)
            cout << "密码正确" << "登录中" << endl;
        else
            cout << "密码错误"<<endl;

    }
    else//pos=NULL时未找到,此时插入改节点
    {
        insertList( user, hash , address ) ;
        cout << "建立改账号" << endl ;
    }

}

void insertList(struct userNode *user, struct hashHead*  hash, int address)
{
    struct listNode *headPos;
    headPos = &hash->theLists[address];

    struct listNode *insertNode;
    insertNode = (struct listNode*)malloc( sizeof( struct listNode  )  )  ;
    insertNode->userMessage = *user ; //将user内容传给改节点
   
    insertNode->next = headPos ;//头插
    headPos = insertNode ;
}


struct listNode *  find(struct userNode *user, struct hashHead*  hash )
{
    int address;
    //计算散列址
    address = atoi( user->account.c_str() ) % hash->tableSize;

    struct listNode *pos ;
    pos = &hash->theLists[address] ;
    while ( !pos->next  && pos->userMessage.account != user->account  )//存在下一个节点且不为key
        pos = pos->next  ;
   
    return pos ;
}

int main()
{
    int N ;
   
    scanf("%d", &N) ;
    struct hashHead* hash;
    hash = initHashTable(10000)  ;

    for (int i = 1; i <= N; ++i)
    {
        userNode *user ;//传引用去掉*
        user = (struct userNode*)malloc(sizeof(struct userNode)) ;
        scanf("%c %s %s", &user->order, &user->account,&user->password  ) ;
        //查找，并输出账号信息，存在，不存在等
        checkAndOutPut(  user )  ;
    }

    return 0  ;
}