C ++结构二进制文件

Question

Hello guys I am new to c++ programming I have saved struct in binary file.. But when try to read it application is crashing Here is my code

struct Person
{
    string name;
    int age;

};
void main()
{
    Person p;
    ifstream is("person.data",ios::binary);
    is.read((char*)&p,sizeof(p));


}

Answer 1

You're using sizeof(p) .

The string class is of variable length. This means it is essentially a struct with a pointer in it to some other characters in the heap. Attempting to read the string in via struct won't work. You have to put all the characters in the struct itself, or it will just read in a (now-dead) pointer to somewhere in the heap and likely cause a segmentation fault.

Try this:

struct Person
{
    char name[40];
    int age;

};
void main()
{
    Person p;
    ifstream is("person.data",ios::binary);
    is.read((char*)&p,sizeof(p));
}

Then use c string functions instead of C++ ones found in cstring or string.h .

Honestly, though, you may want to listen to @πάντα ῥεῖ . You're trying to serialize C structs. Reading data in via struct is a very "C" thing to do, but you're mixing "C++" classes into that. The two paradigms don't mix very well. BOOST has a serialization library , if you really want to serialize C++ classes I would start there.