Dynamic memory in a class (Allocating memory and accessing to the elements)

Question

I have a simple class aClass:

class aClass
{
public:
    aClass(int size)
    {
        condition = new bool[size];
    }
    ~aClass()
    {
        delete condition;
    }
    bool getCondition(int i) const
    {
        return condition[i];
    }

    void setCondition(bool* condition, int i)
    {
        *(this->condition + i) = *condition;
    }
private:
    bool* condition;
};

In fact I defined a bool pointer and using constructor to allocate memory.

#include <iostream>
#include "aClass.h"
using namespace std;

int main()
{
    aClass tempVar(10);
    bool *pC;

    for (int i = 0; i < 10; i++)
    {
        *pC = 0;
        tempVar.setCondition(pC, i);
    }
   for (int i = 0; i < 10; i++)
   {
         cout  <<  tempVar.getCondition(i);
   }
    return 0;
}

I do not know what is the problem in this code.

I used gcc version 4.6.3 to compile the code.

One `delete` per `new`. One `delete[]` per `new[]`. Rule of Three. *mumble mumble* — chris, Jan 04 '14 at 07:36
Oh and you did not actually create the `bool` you assign to in the first loop — user1781290, Jan 04 '14 at 07:37
@user1436187 You should not correct the code in your question, nobody will understand what the answers refer to anymore. Please post your corrected code as answer instead. — , Jan 04 '14 at 07:51

score 4 · Accepted Answer · edited May 23 '17 at 12:03

You are trying to dereference pC although you never initialized the pointer. Probably pC should have type bool, not bool*, at the same time *pC = 0 should likely be pC = 0 and setCondition should likely take bool not bool*.

You delete although it should be delete[], see here why: delete vs delete[]

Your code will try to delete allocated memory twice if an instance of aClass is copied somewhere. See Rule of three.

You should use std::vector instead of the manually allocated array.

Marcelo Cantos · Answer 2 · 2014-01-04T07:50:47.340

There are two mutually exclusive problems here:

You haven't initialized pC. Do this:

int main() {
    ⋮
    bool * pC = new bool;
    ⋮
    delete pC;
}

Actually, raw pointers aren't such a good idea, so this is better:

    std::unique_ptr<bool> pC(new bool);
    // No delete required.

setCondition() doesn't need a pointer parameter at all:

class aClass {
    ⋮
    void setCondition(bool cond, int i) {
        condition[i] = cond;
    }
    ⋮
};

int main() {
    ⋮
    for (int i = 0; i < 10; ++i) {
        tempVar.setCondition(false, i);
    }
    ⋮
}

Dynamic memory in a class (Allocating memory and accessing to the elements)

2 Answers2