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class Matrix
{
private:
    int m_nrows;
    int m_ncols;
    double** m_data;

    void init()
    {   
        m_data = new double*[m_nrows]; 
        for(int i = 0; i < m_nrows; i++) 
            m_data[i] = new double[m_ncols];
    }
// clean up
void free()
    {
        if(m_data != NULL)
           for(int i = 0; i < m_nrows; i++) delete [] m_data[i];
           delete [] m_data;
    }
public:
// constructor
    Matrix(int nrows, int ncols):m_nrows(nrows), m_ncols(ncols) // Zeros
    {
        init();
        for (int i = 0; i < nrows; i++)
            for (int j = 0; j < ncols; j++)
                m_data[i][j] = 0.0;
    }
    Matrix(int nrows, int ncols, const double *val):m_nrows(nrows), m_ncols(ncols) // Initialized by 1D Array
    {
        init();
        for (int i = 0; i < nrows; i++)
            for (int j = 0; j < ncols; j++)
                 m_data[i][j] = *val++;
    }
//Operators =, +
   Matrix & operator = (const Matrix &rhs) 
   {  
       if (this != &rhs){
           if(m_nrows != rhs.m_nrows || m_ncols != rhs.m_ncols){
               m_nrows = rhs.m_nrows;
               m_ncols = rhs.m_ncols;
           }
           free();
           init();
           for (int i = 0; i < m_nrows; i++)
               for (int j = 0; j < m_ncols; j++)
                   m_data[i][j] = rhs.m_data[i][j];
       }
       return *this;
   }
   Matrix operator + (const Matrix &rhs)
   {    
       if (m_nrows == rhs.m_nrows && m_ncols == rhs.m_ncols ){
           Matrix new_mat(m_nrows, m_ncols);
           for (int i = 0; i < new_mat.m_nrows; i++)
               for (int j = 0; j < new_mat.m_ncols; j++)
                   new_mat.m_data[i][j] = m_data[i][j] + rhs.m_data[i][j];
           return new_mat;
       }
       else
           std::cerr << "Operator '+' Matrix dimensions must agree";
   }
};

int main()
{
    double x[6] = { 1, 2, 3, 4, 5, 6};
    Matrix a
    Matrix b(2,3,x);
    Matrix c(2,3,x);

    a = c;
    a.print();
    std::cout<<std::endl;
    c = a+b;
    return 0;
}

Hello,

This code is for doing simple 2d matrix operations. However, I just cannot get the operator "+" right. The rest of code is valid under my testing. There is something wrong, but I just cannot find it. NEED YOUR HELP!

The error message shows * glibc detected * ./a.out: double free or corruption (out): 0x0000000001ec4160 ***. or Segmentation fault: 11 using different compilers.

TensorNetowork
  • 13
  • 2
  • Your class violates the Rule Of Three. See the linked question for more information. Your class must implement a copy constructor, and an assignment operator. – Sam Varshavchik Oct 06 '16 at 03:38
  • I do make the destructor for it. Just didn't post it to save the space. But I don't use either destructor or copy constructor, so does it really matter? – TensorNetowork Oct 06 '16 at 03:43
  • 1
    When did I say anything about a destructor? Of course the copy constructor and the assignment operator matters. Read the linked question. I am not going to repeat all the information that's explained in there. `Matrix m1=m2`. Now both `m1` and `m2` have the same `m_data` pointer, and both's destructors will try to `delete[]` the same pointer. Hillarity ensues. Your compiler does not apparently elide the copy resulting from `operator+`, and does copy-construction on the result. Think hard. – Sam Varshavchik Oct 06 '16 at 03:48
  • Oh! Thanks. You're absolutely right! The copy constructor is IMPORTANT. I'm totally a newbie. Still learning from mistakes! – TensorNetowork Oct 06 '16 at 03:55

0 Answers0