当您具有二维数组（在C ++中）时，调用析构函数的正确方法是什么？

Question

这是我的构造函数：

Matrix::Matrix(int rows, int columns)
{
  elements = new int*[rows];
  for (int x = 0; x < rows; x++)
  {
    elements[x] = new int[columns];
  }
}

这是我的析构函数：

Matrix::~Matrix()
{
    delete elements;
}

我将析构函数更改为说“ delete [] elements”，“ delete * elements”，“ delete elements *”，以及各种组合，每种组合都会冻结程序。 我也尝试过“删除此”，但这也会冻结程序。 我会尝试“ free（）”，但是我听说这是不好的编程习惯，它实际上并没有释放内存。

任何帮助表示赞赏。

Answer 1

这使我没有用valgrind --leak-check=yes泄漏

编辑 ：添加了一个复制构造函数以允许Matrix myMat2 = myMat; 样式调用。 此时，您可能应该在寻找swap样式函数和复制分配运算符。 等等等等...

#include <iostream>

class Matrix
{
    int** elements;
    int rows_;

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

Matrix::Matrix(int rows, int columns)
{
    std::cout<< "Matrix constructor called" << std::endl;
    rows_ = rows;
    elements = new int*[rows];
    for (int x=0; x<rows; x++)
    {
        elements[x] = new int[columns];
    }
}

Matrix::~Matrix()
{
    for (int x=0; x<rows_; x++)
    {
        delete[] elements[x];
    }
    delete[] elements;
    std::cout<< "Matrix destructor finished" << std::endl;
}

Matrix::Matrix(const Matrix &rhs)
{
    std::cout<< "Called copy-constructor" << std::endl;
    rows_ = rhs.rows_;
    columns_ = rhs.columns_;
    elements = new int*[rows_];
    for (int x=0; x<rows_; x++)
    {
        elements[x] = new int[columns_];
        *(elements[x]) = *(rhs.elements[x]);
    }
}

int main()
{
    Matrix myMat(5, 3);
    Matrix myMat2 = myMat;
    return 0;
}

Valgrind输出：

user:~/C++Examples$ valgrind --leak-check=yes ./DestructorTest
==9268== Memcheck, a memory error detector
==9268== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==9268== Using Valgrind-3.10.0.SVN and LibVEX; rerun with -h for copyright info
==9268== Command: ./DestructorTest
==9268== 
Matrix constructor called
Called copy-constructor
Matrix destructor finished
Matrix destructor finished
==9268== 
==9268== HEAP SUMMARY:
==9268==     in use at exit: 0 bytes in 0 blocks
==9268==   total heap usage: 12 allocs, 12 frees, 200 bytes allocated
==9268== 
==9268== All heap blocks were freed -- no leaks are possible
==9268== 
==9268== For counts of detected and suppressed errors, rerun with: -v
==9268== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

Answer 2

您应该遵循@chris的建议。 但是，如果您仍然想知道如何做：

for (int i = 0; i < rows; i++)
{
    delete[] elements[i];
}

delete[] elements;