Copy constractor with memory allocation and deallocation - c++

Question

I have written following piece of code
#include<iostream>
#include<cstring>
using namespace std;
///Driver class
class driver
{
char *name;
int age;
public:
//Default contructor
driver(){}
//Constructor for initialize
driver(int a, char* n)
{
age = a;
int len = strlen(n);
//Allocate memory for name
name = new char[len];
strcpy(name, n);
}
//Copy constructor
driver(const driver &d)
{
name = new char[strlen(d.name)];
strcpy(name, d.name);
age = d.age;
}
void print()
{
cout<<"Name: "<<name<<endl;
cout<<"Age: "<<age<<endl;
}
~driver()
{
if(name != NULL)
{
delete name;
}
}
};
class automobile
{
driver drv;
char* make;
int year;
public:
automobile(driver d, char* m, int y)
{
drv = d;
int len = strlen(m);
make = new char[len];
strcpy(make, m);
year = y;
}
void print()
{
drv.print();
cout<<"Make: "<<make<<endl;
cout<<"Year: "<<year<<endl;
}
~automobile()
{
if(make!=NULL)
{
delete[] make;
}
}
};
int main()
{
driver d(15, "Jakir");
automobile a(d, "Toyta", 1980);
a.print();
return 0;
}
I have to use char* not string and allocate memory dynamically. But when I run the code, there occurs an error of memory leaks. I think it's due to the copy constructor and de-allocation memory of driver class. How to fix the error? Any suggestion is appreciated. Thanks in advance.

Answer 1

There is a lot of stuff wrong with this code, but I will list a few of the big ones.
As smentioned by others, you new char's need to be one bigger than they are.
You default constructor should set name to nullptr.
you have a memory handling error whenever you do an assignment, eg on this line: drv = d; because it calls the default operator=, which is incorrect in your case. Ther eis the Law of the Big Three which loosely states that whenever you need either a (non-trivial) copy constructor, copy assignment operator, or destructor, you'll most likely need to implement the others, too. You need to write an operator=!
Based on existing code, I would expect your operator= to look vaguely like this:
//assignment operator
const driver&operator=(const driver &rhs)
{
if (this==&rhs) return *this;
delete[] this->name;
this->name = new char[strlen(rhs.name)+1];
strcpy(this->name, rhs.name);
this->age = rhs.age;
return *this;
}
Do all that, and your core dump goes away.
PS Please, please just learn to use std::strings, new-ing char arrays and managing the memory yourself is a bad bad move.

Answer 2

name = new char[len+1]; not name = new char[len];
name = new char[strlen(d.name) + 1]; not name = new char[strlen(d.name)];
delete[] not delete
Need to define an assignment operator driver& operator=(const driver &d) in order to follow the rule of three.
Similar changes need to automobile.
However I don't see a memory leak, what makes you think you have one?

Answer 3

In main method you need to do like this,
driver* d = new driver(15, "Jakir");
automobile* a = new automobile (d, "Toyta", 1980);
a->print();
if ( a ) delete a ;
if ( d ) delete d ;
return 0 ;