CODEWITHSUNDEEP
c++parametersoperator-overloadingdestructor
Fekete Ferenc
Fekete Ferenc

Reputation: 119

c++ operator overloading, destructor is called

I am trying to track how many object is created of a given class. If I overload the operator ++ in the class, the destructor is called but I don't know why. To be more specific:

class num{
public:
    virtual void setValue(int)=0;
    static int db;
    num(){}
    ~num(){}
};

int num::db = 0;

class int32: public num{
public:
    // GET
    int getValue();

    // SET
    void setValue(int f);

    // constructor
    int32()
    {
        cout << "Construction..."<<endl;
        this->value = 0;num::db++;
    }

    // destructor
    ~int32()
    {
        cout << "destruction..."<<endl;
        num::db--;
    }

    // operators
    int32 operator++(int);
    int32 operator++(void);

protected:
    int value;
};

int32 int32::operator ++()
{
    this->value++;
    return *this;
}

int32 int32::operator ++(int)
{
    this->value++;
    return *this;
}

int main()
{
    int32 i;
    i.setValue(20);

    cout << (i++).getValue()<<endl;
    cout << (++i).getValue()<<endl;

    cout << num::db;

    cout << endl << "End of execution.";
    return 1;
}

The result is: Construction... 21 destruction... 22 destruction... -1 End of execution.destruction...

So after ++i and i++ a destructor is called, but why?

Thanks a lot!

Upvotes: 1

Views: 1848

Answers (3)

iolo
iolo

Reputation: 1090

It is because your "operator++()" methods both return a copy of a "int32". Thus for every call a new instance is created and returned.

Upvotes: 0

Dariusz
Dariusz

Reputation: 22291

You are returning a copy of the object in the ++ operator.

each time you call return *this you actually create a copy of the object which is passed to the calling code.

Upvotes: 1

Some programmer dude
Some programmer dude

Reputation: 409472

It's because you return a copy. You would want to create a copy constructor.

Upvotes: 3

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