"Debug Assertion" arrays, header files and declarations

Question

I have made a header file which contains an array of a fixed size (17) but there is something fundamentally incorrect and I cannot find what.

ScreenArray.h

    class ScreenArray
    {
    public:
        ScreenArray();
        ~ScreenArray();
        unsigned long getColour(int arrayPointer);
        void setColour(int arrayPointer, unsigned long pixelColour);
    private:
        unsigned long pixelArray[17];
    };

ScreenArray.cpp

#include "PixelScreenArray.h"

ScreenArray::ScreenArray()
{

}

ScreenArray::~ScreenArray()
{
    delete[] pixelArray;
}

unsigned long ScreenArray::getColour(int arrayPointer)
{
    return pixelArray[arrayPointer];
}

void ScreenArray::setColour(int arrayPointer, unsigned long pixelColour)
{
    pixelArray[arrayPointer] = pixelColour;
}

Source.cpp

...
ScreenArray sA;
sA.setPixel(0, 3242);
...

You don't need to `delete` the array as you didn't allocate it with `new` — Roger Rowland, Oct 21 '14 at 04:27

score 1 · Answer 1 · edited May 23 '17 at 12:20

If you didn't allocate the array with new[] you shouldn't delete[] it, this is wrong:

class ScreenArray
{
public:
    ScreenArray();
    ~ScreenArray() {
       delete[] pixelArray; // Nope
    }
private:
    unsigned long pixelArray[17];
};

the array is a member of the class and whether the entire object is allocated on the stack as you did:

ScreenArray sA;
sA.setPixel(0, 3242);

or allocated on the heap with a new ScreenArray();, you can't "just delete part of the object away".

In your specific case you're trying to free stack memory and that's UB

"Debug Assertion" arrays, header files and declarations

1 Answers1