Question

I keep getting the error in VS 2100 “CRT detected that the application wrote to memory before start of heap buffer”

Can anyone help? My int Main is all the way on the bottom. The error occur when the delete [] command is run on the operator= function

#include "intset.h"
const int MAXINITIALSIZE = 5;
int IntSet::numOfArray = 0;

IntSet::IntSet(int a, int b, int c, int d, int e)
{
    numOfArray++;
    int tempArray[] = {a, b, c, d, e};
    size = determineHighest(tempArray) + 1; //determines largest int
    cout << "size is " << size << endl;

    arrayPtr = new bool[size]; //creates array of bool

    for (int i = 0; i < size; i++) //fill bool array 
    {
        arrayPtr[i]= false;  //arrayptr is a bool pointer created in the header
    }   

    for (int i = 0; i < MAXINITIALSIZE; i++)
    {
        arrayPtr[tempArray[i]]= true;
    }

        for (int i = 0; i < size; i++)
    {
        cout << &arrayPtr[i] << endl;
    }
}
IntSet::IntSet(const IntSet &intsetObject)
{
    numOfArray++;
    size = intsetObject.size;

    arrayPtr = new bool[size];

    for (int i = 0; i < size; i++)
    {
        if (intsetObject.arrayPtr[i])
            arrayPtr[i] = intsetObject.arrayPtr[i];
    }
}
IntSet::~IntSet()
{
    --numOfArray;
    delete [] arrayPtr;     
    arrayPtr = NULL;
}

int IntSet::determineHighest(int tempArray[])
{
    int temp = tempArray[0];    
    for (int i = 1; i < MAXINITIALSIZE; i++)
    {
        if (tempArray[i] > temp)
            temp = tempArray[i];
        else
            continue;       
    }
    return temp;
}

IntSet& IntSet::operator=(const IntSet &intsetObject) //ask about IntSet&
{
    cout << "inside operator=" << endl;
    if (&intsetObject != this)
    {
        for (int i = 0; i < size; i++)
        {
            cout << &arrayPtr[i] << endl;
        }
        delete [] arrayPtr;   //HEAP ERROR HERE!
        for (int i = 0; i < size; i++)
        {
            cout << &arrayPtr[i] << endl;
        }
        size = intsetObject.size
        arrayPtr = new bool[size]();
        for (int i = 0; i < size; i++)
        {
            if (intsetObject.arrayPtr[i])
                arrayPtr[i] = intsetObject.arrayPtr[i];
        }
    }
    return *this;
}
ostream& operator<<(ostream &output, const IntSet &intsetObject)
{
    output << "{ ";
    for (int i = 0; i < intsetObject.size; i++)
    {
        if (intsetObject.arrayPtr[i] == true)
        {
            output << i << " ";
        }
        else 
            continue;
    }
    output << "}";
    return output;
}


//main

#include "intset.h"

int main() {

    IntSet object2(9);   

    IntSet object4(3,6);

    object4 = object2;

   return 0;
}

Answer 1

This can only happen if arrayPtr is accessed with a negative index. I suspect your defaults for a,b,c,d,e are -1 in the declaration for IntSet::IntSet, so it is writing to arrayPtr[-1] in the set-true loop. Check for tempArray[i] >= 0 there.

Also, you can’t print the array after you have deleted it, so you should remove those lines after the delete, although they should be “harmless” in that only garbage will be printed, but who knows – the OS could release the page containing the array and it could segfault your program.

Finally, you should not test if (intsetObject.arrayPtr[i]) in the copy & = operators. Otherwise all “false” elements in the source array become uninitialized in the destination array (new bool[size] does not initialize the array to all false).