Problematic code??? Is there a problem with my destructor?

Question

Hi, My code compiles and run, but i've been told that it is quite problematic. I don't understand where do i go wrong.

Also, isn't it suppose to be wrong to declare "char _arrName[2];" and to do the assignment "_arrName[2]= '\0';" ? Isn't is a "out of boundaries" bug?

#include <iostream>
using namespace std;
class Base {
protected:
char* _name;
public:
virtual ~Base() { cout << "Base dtor of " << _name << endl; };
};
class D1: public Base {
char _arrName[2];
public:
D1() {
_name= _arrName;
_arrName[0]= 'D';
_arrName[1]= '1';
_arrName[2]= '\0';
}
virtual ~D1() { cout << "D1 dtor" << endl; }
};
int main () {
Base* arr[2];
arr[0]= new D1();
delete arr[0];
}

Answer 1

There is nothing wrong with your code. Perhaps it is because you haven't indented your code, which makes it 100x harder to read.

Though, some suggestions I would suggest you use std::string instead of plain C-style strings. It makes your job much easier.

Answer 2

Yes, there is a definite error on this line.

_arrName[2]= '\0';

_arrName is an array of two char so you can only use the two values _arrName[0] and _arrName[1]. _arrName[2] is out of bounds.

Also there is an issue with this line.

virtual ~Base() { cout << "Base dtor of " << _name << endl; };

Because the derived class has pointed _name to point at an array member of the derived class, by the time ~Base() is called this array will have been destroyed and _name will no longer be pointing at a valid array.

There's the potential for error in the base class. _name is never initialized so it relies on derived classes initializing it. This is less than ideal design, although in practice it may or may not cause a real problem.