Question

运行以下程序时出现此错误（它完美地执行代码，但看起来有一些关于指针/内存的问题）。提前感谢您的帮助...

这是我得到的信息：

REVIEW（8310）malloc： *对象0x100103b80的错误：未释放指针被释放 * 在malloc_error_break中设置断点以进行调试（lldb）

我的代码：

在文件Matrix.h中

template <typename T>
class Matrix
{

   private:
T** M;
// unsigned numCol, numRow;
unsigned minRowIndex, maxRowIndex;
unsigned minColIndex, maxColIndex;




public:

Matrix();  // default constructor



Matrix(const unsigned& _numRow,
       const unsigned& _numCol,
       const T& value,
       const unsigned& _minRowIndex = 0,
       const unsigned& _minColIndex = 0);

~Matrix();


void Print();

T& operator() (const unsigned& row, const unsigned& col);

};

 template<typename T>
 Matrix<T> :: Matrix()

 {

     maxRowIndex = 9;
     maxColIndex = 9;

      unsigned i,j;

      M = new T*[maxRowIndex + 1];

     for (i =  minRowIndex; i < maxRowIndex; i++)
          M[i] = new T[maxColIndex + 1];

     for (i = minRowIndex; i < maxRowIndex; i++)
         for (j = minColIndex; j < maxColIndex; j++)
              M[i][j] = 0;

  }

   template<typename T>
    Matrix<T> :: Matrix( const unsigned& _numRow,
                 const unsigned& _numCol,
                 const T& value,
                 const unsigned& _minRowIndex,
                 const unsigned& _minColIndex)

   {

       minRowIndex = _minRowIndex;
       minColIndex = _minColIndex;
        maxRowIndex = _minRowIndex + _numRow - 1;
            maxColIndex = _minColIndex + _numRow - 1;

     unsigned i,j;

        M = new T*[maxRowIndex + 1];

      for (i =  minRowIndex; i <= maxRowIndex; i++)
          M[i] = new T[maxColIndex + 1];

      for (i = minRowIndex; i <= maxRowIndex; i++)
           for (j = minColIndex; j <= maxColIndex; j++)
               M[i][j] = value;
 }


 template<typename T>
 Matrix<T> :: ~Matrix()
 {
       for (unsigned i = 0; i <= maxRowIndex; i++)
           delete[] M[i];

        delete[] M;
 }


 template<typename T>
 void Matrix<T> :: Print()
 {
        unsigned i,j;

       for (i = minRowIndex ; i <= maxRowIndex; i++)
           for (j = minColIndex; j <= maxColIndex; j++)
       {
         cout << M[i][j] << "   ";

         if (j == maxColIndex)
            cout << endl;
       }

   cout << endl;cout << endl;

 }

   template<typename T>
   T& Matrix<T> :: operator() (const unsigned& row, const unsigned& col)
    {
          return  M[row][col];
    }

在文件main.cpp中

      #include "Matrix.h"


      using namespace std;

  int s(Matrix<int> L)
   {

      return L(2,2);
   }



 int main()
 {

     Matrix<int> L (5,5,100);
     cout << "L(2,2) = " << s(L) << endl << endl;

     return 0;    
 }

Answer 1

使用new和delete分配字段的类应具有复制构造函数和重载operator=。如果不这样做，将使用默认表单，其中只复制字段。

在您的情况下，T** M在调用s(L)期间被复制，并且在返回时，副本被破坏，导致删除所有数组。在main的末尾，发生了另一次破坏，但现在指针指的是已经释放的块。

对于函数s，您也可以传递引用以避免复制（但这不能解决一般问题）。

矩阵指针释放问题

1 个答案: