求解C++析构函数释放内存错误原因，头疼。

拜托看一下我这个矩阵类实现里的析构函数哪里错了，编译没问题，运行出错。
删掉析构函数就可以运行了，为什么呢？

#include
using namespace std;
class CMatrix
{
public:
CMatrix(int, int); //构造函数
void output(); //输出矩阵各元素
CMatrix operator +(CMatrix &M2); //重载矩阵加运算
CMatrix operator -(CMatrix &M2); //重载矩阵减运算
friend istream & operator>>(istream &, CMatrix &);
friend ostream & operator<<(ostream &, CMatrix &);
~CMatrix()
{
delete[] m_pData;
}
private:
int m_row; //矩阵行数
int m_col; //矩阵列数
double *m_pData; //使用指针指向矩阵各元素
};
//构造函数
CMatrix::CMatrix(int r, int c)
{
m_row = r;
m_col = c;
m_pData = new double[r*c];
for (int i = 0; i<m_row*m_col; i++)
m_pData[i] = 0;
}
//矩阵输出函数
void CMatrix::output()
{
int j = 0;
for (int i = 0; i<m_row*m_col; i++)
{
cout << m_pData[i] << " ";
if ((i + 1) % m_col == 0)
cout << endl;
}
}
//重载矩阵相加运算
CMatrix CMatrix::operator +(CMatrix &M2)
{
CMatrix M(m_row,m_col);
for (int i = 0; i<m_row*m_col; i++)
M.m_pData[i] = m_pData[i] + M2.m_pData[i];
return M;
}
//重载矩阵相减运算
CMatrix CMatrix::operator -(CMatrix &M2)
{
CMatrix M(this->m_row,this->m_col);
for (int i = 0; i<m_row*m_col; i++)
M.m_pData[i] = m_pData[i] - M2.m_pData[i];
return M;
}
istream & operator>>(istream &input, CMatrix &c)
{
for (int i = 0; i < c.m_row*c.m_col; i++)
input >> c.m_pData[i];
return input;
}
ostream & operator<<(ostream &output, CMatrix &c)
{
for (int i = 0; i < c.m_row*c.m_col; i++)
{
output << c.m_pData[i];
if ((i + 1) % c.m_col == 0)
output << endl;
}
return output;
}
int main()
{
CMatrix M1(2, 2), M2(2, 2), M3(2, 2);
cin >> M1;
cout << M1;
cin >> M2;
cout << M2;
M3 = M1 + M2;
cout << M3;
M3 = M1 - M2;
cout << M3;
return 0;
}

http://bbs.csdn.net/topics/370209063

具体报的什么错误呢

 ~CMatrix()
{
delete[] m_pData;   //这里可以为空，不能释放，因为没使用一次就释放了，下次在使用时指针为空。。
}

如果真想释放内存，建议写一个函数释放，在变量彻底不使用时释放！！！

CMatrix& CMatrix::operator +(CMatrix &M2)
{
CMatrix M(m_row,m_col);
for (int i = 0; i<m_row*m_col; i++)
M.m_pData[i] = m_pData[i] + M2.m_pData[i];
return M;

}

CMatrix::CMatrix(CMatrix& a)
{
this->m_row = a.m_row;
this->m_col = a.m_col;
this->m_pData = new double[a.m_col * a.m_row];
memcpy(this->m_pData, a.m_pData, a.m_col * a.m_row);
}
加一个引用就可以了，或者加一个拷贝构造函数就可以了