为什么代码在析构函数中失败?

我已经讨论过类似于“为什么调用析构函数两次?”.我的问题可以是类似的,但有一点变化。运行以下代码时出错:

struct Employee{
        char *name;
        char *tag;
        Employee *employee;

        Employee(){
            name = NULL;
            tag = NULL;
            employee = NULL;
        }
        //copy constructor
        Employee(const Employee &obj){
            cout << "Copy constructor called" << endl;
            name = (char*)malloc(sizeof(char)*strlen(obj.name));
            strcpy(name, obj.name);
            tag = (char*)malloc(sizeof(char)*strlen(obj.tag));
            strcpy(tag, obj.tag);
            employee = (struct Employee*)malloc(sizeof(obj.employee));
            employee = obj.employee;
        }
        //overloaded assignment operator
        void operator = (const Employee &obj){
            cout << "Assignment operator called" << endl;
            if (this == &obj){
                return;
            }
            strcpy(name, obj.name);
            strcpy(tag, obj.tag);
            employee = obj.employee;

        }
        //destructor
        ~Employee(){
            cout << "Destructor called" << endl;
            if (name != NULL){
                cout << "Freeing name" << endl;
                free(name);
                name = NULL;
            }
            if (tag != NULL){
                cout << "Freeing tag" << endl;
                free(tag);
                tag = NULL;
            }
            if (employee != NULL){
                cout << "Freeing employee" << endl;
                free(employee);
                employee = NULL;
            }
        }
};
Employee createNode(){
        Employee emp;
        emp.name = (char*)malloc(sizeof(char)* 25);
        strcpy(emp.name, "Alan");
        emp.tag = (char*)malloc(sizeof(char)* 25);
        strcpy(emp.tag, "Engineer");
        emp.employee = (struct Employee*)malloc(sizeof(struct Employee));//just created memory, no initialization
        return emp;
}
Employee get(){
        //Employee emp = createNode();
        //return emp;
        return createNode();
}

int main(){
        Employee emp = get();

        getchar();
        return 0;
}

我调试了代码,发现当第二次调用析构函数时,当主函数退出时,错误会出现。

1)我想知道为什么代码不能运行?

2)是否有内存泄漏?

3)如何正确修复错误解除内存分配?

事先谢谢。

更新:

根据这三条规则,我还添加了一个复制构造函数,并重载了赋值运算符。但是错误(表达式:_crtisvalidheappointer(puserdata))正在引发。在检查了谷歌之后,我可以看到堆腐败发生的地方。当我在createNode()中对结构成员employee的初始化进行注释时,我可以看到试图在析构函数中释放该employee时出现的错误。所以我怀疑问题出在雇员结构成员身上。请帮助我。我正在使用Visual Studio进行调试和运行。