Using new and delete on object arrays C++

Question

Does delete call the destructor? I have modified the code on the first answer a little bit, but i can't catch my wrong. It is being compiled with 0 errors but program crashes when i run it, also devC++ debug mode gives me SIGTRAP signal. I'd really appreciate a second hand here.

So the idea is; reform() will delete the old array (if necessary, the second parameter is optional and i'm only using it in constructors because at that moment the pointer is actually null (?)). And then it will allocate it again with new, using the input parameter size. I really have no idea which part might be wrong. Thanks for all answers.

#include <iostream>

using namespace std;

class A
{
    private:
        int val;
    public:
        A();
        int GetVal();
        void SetVal(int Val);
};

A::A()
{
    this->val = 0;
}

int A::GetVal()
{
    return this->val;
}

void A::SetVal(int Val)
{
    this->val = Val;
}


#define DEF_A_SIZE 1

class B
{
    private:
        A *a_s;
        int aSize;
        int aCount;
        void reform(const int size, int dlt = 1);
public:
    B();
    ~B();
    void SetSize(const int newSize);
    int GetSize();
    void AddA(A a);
    A GetA(int index);
};

void B::reform(const int size, int dlt)
{
    if(dlt)
    {
        delete[] (this->a_s);
    }
    this->a_s = new A[size];
    this->aCount = 0;
    this->aSize = size;
}

B::B()
{
    reform(DEF_A_SIZE, 0);
}

B::~B()
{
    delete [] (this->a_s);
}

void B::SetSize(const int newSize)
{
    reform(newSize);
}

int B::GetSize()
{
    return this->aSize;
}

void B::AddA(A a)
{
    if (aCount < aSize)
    {
        this->a_s[aCount].SetVal(a.GetVal());
        aCount++;
    }
}

A B::GetA(int index)
{
    if (index < aCount)
    {
        return this->a_s[index];
    }
}

#define B_NUM 1

class C
{
    private:
        B *b_s;
        int bc;
        int bs;
        void reform(const int size, int dlt = 1);
    public:
        C();
        ~C();
        void addb(B b);
        B getB(int index);
};

void C::reform(const int size, int dlt)
{
    if (dlt)
    {
        delete [] (this->b_s);
    }
    bc = 0;
    bs = size;
    b_s = new B[size];
}

void C::addb(B b)
{
    if (bc < bs)
    {
        b_s[bc].SetSize(b.GetSize());
        for (int i = 0; i < b.GetSize(); i++)
        {
            b_s[bc].AddA(b.GetA(i));
        }
        bc++;
    }
}

B C::getB(int index)
{
    if (index < bc)
    {
        return b_s[index];
    }
}

C::C()
{
    reform(B_NUM, 0);
}

C::~C()
{
    delete [] (this->b_s);
}

int main()
{
    C *cptr = new C();

    B b = B();
    b.SetSize(2);

    A a = A();
    a.SetVal(10);
    b.AddA(a);

    A a2 = A();
    a2.SetVal(20);
    b.AddA(a2);

    cptr->addb(b);

    cout << cptr->getB(0).GetA(0).GetVal() << endl;
    cout << cptr->getB(0).GetA(1).GetVal() << endl;

    delete cptr;

    cin.get();

    return 0;
}

Solved

Turns out my problem was my Add or Get functions. I changed them this way; Getters will return references to the respective objects (e.g B &getB(int index);) And Adder's will take pointers as parameters, not objects ( or values ) (e.g void addb(B *b);)

Where exactly is your code crashing? It appears that you are not initialising a_s to 0 in your B constructor, and when you call reform it attempts to delete[] a_s which is set to garbage values. Try intialising a_s to 0 (or nullptr in c++11). If that fails, put a breakpoint in your code and watch the line it crashes on. — Tas
– Tas, Commented Apr 30, 2015 at 23:16
I thought i took care of that by using the second parameter to reform function, in B constructor i'm calling reform this way->reform(DEF_A_SIZE, 0); Which should not delete a_s, i'm trying random stuff right now like changing getters of A and B placed in B and C respectively to reference getters by putting & before them. Now my code actually gets to the very end. Then i press enter for cin.get() and i take segmentation fault. — Ahmetcan Turker
– Ahmetcan Turker, Commented Apr 30, 2015 at 23:38

πάντα ῥεῖ · Accepted Answer · 2015-04-30 23:12:10Z

0

"Does delete call the destructor?"

Yes, delete or delete[] calls the destructor function of affected class instances.

answered Apr 30, 2015 at 23:12

πάντα ῥεῖ

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1 Comment

Ahmetcan Turker Over a year ago

That was not my question though. I modified the code that took place in that page, so instead of copy-pasting the code that was there, i used the link. I did not know stack overflow would print the link's shown name (or whatever)

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