matrixes

//Hello, I am still having problem with leaks.
//Caused by createNew method and passing reference argument

#include <cstdlib>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <iostream>
#include <fstream>
#include <cstring>
#include <sstream>
#include <map>
using namespace std;

class GeneralMatrix {
protected:
    int width;
    int height;

public:

    //Stores values of matrix size
    GeneralMatrix(int nr, int nc) {
        height = nr;
        width = nc;
    }
    virtual ~GeneralMatrix(){
    }

    GeneralMatrix & add(const GeneralMatrix & m2) {
        //Check for compatible matrixes
        if (height != m2.height || width != m2.width) {
            cout << "Matrix sizes must match!" << endl;
            return *this;
        }
        //Create new empty matrix
        GeneralMatrix &m3 = createNew(height, width);
        //Set every number to sum of this and given matrix
        for (int i = 0; i < height; i++) {
            for (int j = 0; j < m2.width; j++) {
                double val = m2.get(i, j);
                if (val != 0) {
                    val += get(i, j);
                    m3.set(i, j, val);
                }
            }
        }
        return m3;
    }
};

class RegularMatrix : public GeneralMatrix {
protected:
    vector<double>data;

public:
    //Constructor
    RegularMatrix(int nr, int nc, const vector<double>& nums) : GeneralMatrix(nr, nc) {
        data = nums;
    }

    GeneralMatrix & createNew(int row, int col) {
        int n = row*col;
        //Prepare vector of zeros
        vector<double>zeros;
        for (int i = 0; i < n; i++) {
            zeros.push_back(0);
        }
        //Call constructor
        GeneralMatrix *ret = new RegularMatrix(row, col, zeros);
        return *ret;
    }


};

int main(int argc, char** argv) {
 double mm3[] = {10, 2, 3, 0, 0, 8, 0, 4, 2, 2, 6, 0, 0, 0, 0, 5};
 vector<double>k;

 for (int i = 0; i < 16; i++) {
     k.push_back(mm3[i]);

 }
 GeneralMatrix *d = new RegularMatrix(4, 4, k);

 (*d).add(*d);
 delete d;
    return 0;
}