Breakpoint exception when using destructor on an object than contains char string

Question

I've got a problem. When i'm starting my program, it works great, but when it proceeds it says that there is a breakpoint error. Then it says that there is a problem with a memory allocation so it's not working. Here is the code: Header:

#pragma once

#include <iostream>
#include <string>

class basics
{
private:
    char *str;
    int len;
    static int string_obj;
public:
    basics() { str = "ces", len = strlen(str), string_obj = 1; }
    basics(const basics &st);
    basics(const char *s);
    ~basics();
    friend std::ostream & operator<<(std::ostream &os, const basics &st);
};

Class functions:

#include "basics.h"
int basics::string_obj = 0;


basics::basics(const char *s)
{
    string_obj++;
    len = std::strlen(s);
    str = new char[len + 1];
    std::strcpy(str, s);
    std::cout << string_obj << " objects was created." << std::endl;
}

basics::basics(const basics & st)
{
    string_obj++;
    len = std::strlen(st.str);
    str = new char[len + 1];
    std::strcpy(str, st.str);
    std::cout << string_obj << " objects was created." << std::endl;
}

basics::~basics()
{
    std::cout << string_obj << " objects was created. Now we'll delete one      of them." << std::endl;
    --string_obj;
    std::cout << string_obj << " objects left." << std::endl;
    delete[] str;
}

std::ostream & operator<<(std::ostream &os, const basics &st)
{
    os << st.str;
    return os;
}

Calling part:

#include "basics.h"

int main()
{
    basics gigas("fear");
    basics cop(gigas);
    gigas.~basics();
    system("pause");
    return 0;
}

While you don't show anything about the specifics of what error you get, I can imagine the issue here is your explicit call to gigas.~basics(); The destructor will be automatically called for you on scope exit. So you're calling it twice. And delete[] on an already deleted pointer can kind of do whatever. Crashing in this case. — Enrico Granata
– Enrico Granata, Commented Feb 7, 2016 at 19:16
If you just default construct your class, then delete will be called on memory not allocated by new. — Richard Critten
– Richard Critten, Commented Feb 7, 2016 at 19:16
You need to read about the rules of three, five and zero. And then stop using character pointers for string and change to std::string. — Some programmer dude
– Some programmer dude, Commented Feb 7, 2016 at 19:17
Thanks a lot! I've been working on the old compiler for some months and there was no auto-destructors. So, i used to write them manually. P.S. Character pointers was some kind of experiment, in other cases i'll use std::string, of course :) — Roman Krylov
– Roman Krylov, Commented Feb 7, 2016 at 19:25

πάντα ῥεῖ · Accepted Answer · 2016-02-07 19:15:44Z

4

Don't call the destructor explicitly:

gigas.~basics();

It will be called automatically when the scope is left. Thus the crash appears because it's called in fact twice.

answered Feb 7, 2016 at 19:15

πάντα ῥεῖ

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