std :: vector中的内存泄漏代表2D数据

Question

我编写了一个简单的模板化Matrix类,用于操作数据基质的主应用程序.截断的Matrix代码是:

template <typename T> 
class Matrix{
   private:
      std::vector<T> matrixRepresentation;
      bool transposed;
  public: 
  Matrix(int r, int c);
  int maxRows;
  int maxCols;
  void setMatrixValue(int row, int col, T val);
  T getMatrixValue(int row, int col);
};

template <typename T>
Matrix<T>::Matrix(int r, int c){
   maxRows = r;
   maxCols = c;
   matrixRepresentation.resize((r+1)*(c+1));
}   

template <typename T>
void Matrix<T>::setMatrixValue(int row, int col, T val){
   matrixRepresentation[row + col*maxCols] = val;
}

template <typename T>
T Matrix<T>::getMatrixValue(int row, int col){
   return matrixRepresentation[row + col*maxCols];
}

正如您所看到的,我只是将2D矩阵表示为向量,并提供包装方法来隐藏该事实.即使我将堆栈变量matrixRepresentation调整为

(r+1)(c+1)

我最后在代码中遇到了内存损坏问题,valgrind告诉我以下内容:

==3753==    at 0x8049777: Matrix<int>::setMatrixValue(int, int, int) (in a.out)
==3753==    by 0x8049346: DataFile::readAllData() (ina.out)
==3753==    by 0x8049054: DataFile::DataFile(char const*) (in a.out)
==3753==    by 0x804C386: main (in a.out)
==3753==  Address 0x42cc970 is 0 bytes after a block of size 5,600 alloc'd
==3753==    at 0x4026351: operator new(unsigned int) (vg_replace_malloc.c:255)
==3753==    by 0x804A603: __gnu_cxx::new_allocator<int>::allocate(unsigned int, 
            void   const*) (in /a.out)
==3753==    by 0x8049F0D: std::_Vector_base<int, std::allocator<int> 
            >::_M_allocate(unsigned int) (in a.out)
==3753==    by 0x804A181: std::vector<int, std::allocator<int> 
            >::_M_fill_insert(__gnu_cxx::__normal_iterator<int*, std::vector<int, 
            std::allocator<int> > >, unsigned int, int const&) (in a.out)
==3753==    by 0x8049AEF: std::vector<int, std::allocator<int> 
            >::insert(__gnu_cxx::__normal_iterator<int*, std::vector<int, 
            std::allocator<int> > >, unsigned int, int const&) (in a.out)
==3753==    by 0x80499AB: std::vector<int, std::allocator<int> >::resize(unsigned int,
            int) (in a.out)
==3753==    by 0x8049709: Matrix<int>::Matrix(int, int) (in a.out)
==3753==    by 0x80492AD: DataFile::readAllData() (in a.out)
==3753==    by 0x8049054: DataFile::DataFile(char const*) (in a.out)
==3753==    by 0x804C386: main (in a.out)

readAllData()方法(此矩阵类的用户)只是从文本文件中读取并尝试填充矩阵

void DataFile::readAllData(){
   int currentValue;
   featureMatrix = new Matrix<int>((theHeader.totalNumSamples),
   (theHeader.numFeatures));

    if (infile.is_open()){
       if (!infile.eof()){
          for (int row=0; row < theHeader.totalNumSamples; row++){
            for (int col=0; col < theHeader.numFeatures; col++){
               infile >> currentValue;
               featureMatrix->setMatrixValue(row, col, currentValue);
             }
          }
       }
       else{
          cout << "EOF reached before we should have been done!  Closing file";
          infile.close();
       }
   }
   else cout << "File not open when attempting to read data";

   infile.close();
}

标头值有效(例如,theHeader.totalNumSamples = 15,theHeader.numFeatures = 100).

如果我能提供更多信息,请告诉我,我真的可以使用一些帮助.

Answer 1

此代码段(在代码中出现两次):

 [row + col*maxCols]

不对.它应该是[row * maxCols + col]或[col*maxRows + row]

就此而言,您不需要matrixRepresentation.resize((r+1)*(c+1)); 分配,而是可以分配matrixRepresentation.resize(r*c);

你应该对极端情况进行数学计算(比如访问元素(maxRows-1,maxCols-1)以便自己检查一下以便理解).