0xC0000005: Access violation reading location 0xFDFDFDED

Question

So I wrote this: Matrix.h:

#pragma once
class Matrix
{
private:
int m, n;
double** M = nullptr;


public:
Matrix();
Matrix(int,int);
Matrix(const Matrix&);
~Matrix();

void set_m(int);
void set_n(int);
int get_m() const;
int get_n() const;
void setM(double**,int,int);
double** getM() const;
void show();
Matrix operator*(Matrix&) const;

};

Matrix.cpp:

#include "Matrix.h"
#include<iostream>

using namespace std;

/*

*/

Matrix::Matrix()
{

set_n(1);
set_m(1);
delete[] M;
M = new double*[get_m()];
for (int i = 0; i < m; i++) {
    M[i] = new double[get_n()];
}
for (int i = 0; i < m; i++)
    for (int j = 0; j < n; j++) M[i][j] = 1.0;

}

Matrix::Matrix(int m_,int n_)
{

set_n(n_);
set_m(m_);
delete[] M;
M = new double *[get_m()];
for (int i = 0; i < m; i++) {
    M[i] = new double[get_n()];
}
for (int i = 0; i < m; i++)
    for (int j = 0; j < n; j++) M[i][j] = 1.0;

 }

 Matrix::Matrix(const Matrix& M_)
 {

set_n(M_.get_n());
set_m(M_.get_m());
delete[] M;
M = new double*[get_m()];
for (int i = 0; i < m; i++) {

    M[i] = new double[get_n()];
}
for (int i = 0; i < m; i++)
    for (int j = 0; j < n; j++) M[i][j] = M_.getM()[i][j];

}

void Matrix::set_m(int m_) {
if (m_ > 0)
    m = m_;
else
    m = 1;
}

void Matrix::set_n(int n_) {
if (n_ > 0)
    n = n_;
else
    n = 1;
}

double** Matrix::getM() const {
return M;
}

Matrix Matrix::operator*(Matrix &M_) const
{
if (get_n() != M_.get_m()) {
    if (get_m() != M_.get_n()) return Matrix();
    else {
        Matrix T(*this);
        return M_*T;
    }
}
else {
    //n = m
    Matrix R(get_m(), M_.get_n());
    for (int i = 0; i < get_m(); i++) {
        for (int j = 0; j < M_.get_n(); j++) {
            double res = 0;
            for (int k = 0; k < get_n(); k++) {
                res += getM()[i][k] * M_.getM()[k][j];
            }
            R.getM()[i][j] = res;
        }
    }
    return R;
}
}

int Matrix::get_m() const {
return m;
}

int Matrix::get_n() const {
return n;
}

void Matrix::setM(double** M_, int m_, int n_) {
set_m(m_);
set_n(n_);
for (int i = 0; i < get_m(); i++) {
        delete M[i];
}
    delete[] M;

M = new double*[m_];
for (int i = 0; i < m; i++) {
    M[i] = new double[n_];
}
for (int i = 0; i < m_; i++)
    for (int j = 0; j < n_; j++) M[i][j] = M_[i][j];
}

void Matrix::show() {
for (int i = 0; i < get_m(); i++) {
    for (int j = 0; j < get_n(); j++) {
        cout << getM()[i][j]<<" ";
    }
    cout << endl;
}
}

Matrix::~Matrix()
{
for (int i = 0; i < get_m(); i++) {
    delete M[i];
}
delete[] M;
}

It crashes at void Matrix::setM(...) when I try to delete M[i] for i = 1; it doe perfectly fine for i=0; but crashes later and I do not have a rational explanation why does it do that. I can see the debugger showing me that the memory cannot be read even before it actually crashing but I do not understand how to fix it. Thanks in advance!

my guess is that get_m is returning different values. Use std::vector anyway — pm100, Jan 28 '16 at 22:09
If you're seeing 0xfdfdfdfd you have a memory overwrite somewhere. http://stackoverflow.com/questions/127386/in-visual-studio-c-what-are-the-memory-allocation-representations — Retired Ninja, Jan 28 '16 at 22:09
Your `Matrix` lacks an assignment operator. Also, most of this code could be replaced with a simple `std::vector>`. And last, show us the `main` program that exercises this class. — PaulMcKenzie, Jan 28 '16 at 22:12

score 0 · Answer 1 · answered Jan 28 '16 at 22:12

0

You are setting your m before deleting your array based on the old value of m and end up deleting your old array using the new value of m. You should first delete your array, then set mm, and then create your new array.

answered Jan 28 '16 at 22:12

Jim Buck

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0xC0000005: Access violation reading location 0xFDFDFDED

1 Answers1