使用c ++文件处理从文件读取时发生异常错误

该程序以字符串（学生姓名）为输入，根据文件中已经存在的学生人数生成该学生的卷号。然后将此信息作为结构存储在该文件中。进一步的细节在注释中。这段代码可以正常工作，直到我更改其中任何一个->

1. 在main（）函数中，如果我发送“数据集”作为引用，则可以正常工作。但是，如果我将其作为副本发送，则意味着每次创建一个用于写入和读取文件的类的新对象（很好，不是吗？），这是一个例外。
2. 在rollGen（）函数中，我创建了班级数据的对象临时数，以计算该文件中已存在数据的学生人数。如果该对象是动态创建的，则代码正在运行。但是，如果我是静态创建的，则程序会给出异常（例如，请参见注释）。我想知道，为什么会发生这种情况？这是与范围相关的事情……还是其他。提前致谢。例外-

    #include<iostream>
    #include<string>
    #include<fstream>

    struct student
    {
        char RollNo[8];
        std::string name;
    };

    class data
    {
        student stu;
    public:
        data() {}
        //open a file for fstream in argument...mod = 0 for input mode...mod = 1 for output mode
        void openn(int mod, std::fstream* yo_fp)    
        {
            if (mod == 0)
            {
                yo_fp->open("cs.txt", std::ios::in);
            }
            else if (mod == 1)
            {
                yo_fp->open("cs.txt", std::ios::out | std::ios::app);
            }
        }
        //generates roll number of student 
        //for example if data of 3 students is already present in file then roll number of new student will be cs4
        void rollGen()
        {
            std::fstream* rg_fp = new std::fstream;
            openn(0, rg_fp);
            int i = 1;
            data* temp = new data;  
            //if I allocate temp on stack...like, 'data temp;' and then in while loop replace 'temp' with '&temp'...programm is giving exception
            //counting number of students whose data is already present in file
            while (rg_fp->read((char*)temp, sizeof(data)))
            {
                i++;
            }
            strcpy_s(stu.RollNo, "cs"); 
            std::string s = std::to_string(i);
            strcat_s(stu.RollNo, s.c_str());
            rg_fp->close();
            delete rg_fp;
        }
        //take name string as input and call roll number generation function. hence providing data to student stu struct present in this class
        void input()
        {
            std::cout << "Enter your name - ";
            getline(std::cin, stu.name);
            rollGen();
            std::cout << "your RollNo is - " << stu.RollNo << std::endl;
        }
        //printing tha data of student stu struct present in class
        void output()
       {
            std::cout << "roll no - " << stu.RollNo << std::endl;
            std::cout << "name - " << stu.name << std::endl;
        }
    };
    //write the data of class object into file after calling input() function
    //using 'data stud' in argument instead of 'data& stud' gives exception
    void write(data& stud, std::fstream* cur_fp)
    {
        stud.input();
        stud.openn(1, cur_fp);
        cur_fp->write((char*)&stud, sizeof(data));
        std::cout << std::endl;
        cur_fp->close();
    }
    //printing all elements of file one by one
    //using 'data stud' in argument instead of 'data& stud' gives exception
    void read(data& stud, std::fstream* cur_fp)
    {
        stud.openn(0, cur_fp);
        std::cout << "Data in File is - " << std::endl << std::endl;;
        while (cur_fp->read((char*)&stud, sizeof(data)))
        {
            stud.output();
            std::cout << std::endl;
        }
        cur_fp->close();
        std::cin.get();
    }

    int main()
    {
        std::fstream *fp = new std::fstream;
        data stud;
        write(stud, fp);
        write(stud, fp);
        read(stud, fp);
        delete fp;
    }