Exception thrown at 0x7B37FF80 (ucrtbased.dll) in Class 12.exe: 0xC0000005: Access violation reading location 0x00B64F88. occurred


I am fairly new to c++. I am using the Visual Studio IDE. I am learning how to send objects to files and how to retreive them. While retrieving so i get an Exception at that place. I don't know what to do

#include <iostream>
#include <fstream>

class Entity 
    int ID;
    const char* name;

    Entity(): ID(-1), name("NOT ASSIGNED") {}
    Entity(int a, const char* b) : ID(a), name(b) {}

std::ostream& operator<<(std::ostream& stream, Entity &e) 
    stream << e.ID << " " << e.name << std::endl; //exception is thrown here
    return stream;

void WriteToFile(Entity e)
    std::cout << "Writing to file\n";
    std::ofstream fout("ENTITY.txt", std::ios::app|std::ios::binary);
    fout.write((char*)&e, sizeof(e));

void ReadFromFile()
    std::ifstream fin("ENTITY.txt", std::ios::binary | std::ios::in);
    while (!fin.eof())
        Entity a;
        fin.read((char*)&a, sizeof(a));
        std::cout << a;

int main()
    Entity a(1, "A");
    Entity b(15, "C");
    Entity x;

asked on Stack Overflow Jun 21, 2020 by Iyappan Sriram

1 Answer


I don't know where you are learning from but it isn't very good if it doesn't tell you that istream::read and ostream::write cannot be used for objects such as Entity.

In order to work with read and write an object must be a POD type, POD stands for plain old data. Additionally anything with a pointer isn't going to work (because write will write the pointer itself, not what the pointer is pointing at, and the pointer value is unlikely to be valid when read again by read).

What you are trying to do is called serialization, and it's more complex in C++ than in some other languages. Because of this you should probably look at a serialization library. For instance boost serialization

answered on Stack Overflow Jun 21, 2020 by john • edited Jun 21, 2020 by john

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