double free 或 corruption (out) 以及如何检查析构函数是否正常工作 [英] Double free or corruption (out) and how to check whether a destructor works properly

问题描述

我正在尝试改进我的二维数组 使用类创建.所有方法都工作正常，它被正确打印出来等等，但是当我尝试创建一个析构函数时，我要么得到一个错误double free or corruption，我能够摆脱错误消息，但是那么我不确定内存是否已正确解除分配，因为我使用了两个 new 关键字但只有一个 delete.

I am trying to improve my 2D array to be created using a class. All methods work fine, it is properly printed out and so on, but when I try to create a destructor I either get an error double free or corruption, I am able to get rid of the error message but then I am not sure whether the memory has been de-allocated properly, because I am using two new keywords but only one delete.

这是我的类声明:

#pragma once    
class myPlan 
{ 
    int slots; 
    int rows = 3;
  
    int **cell; 
  
public: 
    myPlan(int slots);   // Constructor 
    ~myPlan();
}; 

这里是定义

#include "myPlan.hpp"

myPlan::myPlan(int slots) 
{ 
    this->slots = slots;
  
    // Create a dynamic array of pointers 
    cell = new int* [rows]; 
  
    // Create a row for every pointer 
    for (int i=0; i<slots; i++) 
    { 
       cell[i] = new int[slots];  
    } 
   for(int i =0; i<3; i++)
   {
    for (int j=0; j<slots; j++) 
    { 
       cell[i][j] = 0;  //setting all cells to zero
    }
   }

} 

//this destructor works
myPlan::~myPlan()
{

   std::cout<<"preparing for destruction"<<std::endl;
        delete[] cell;
   
   std::cout<<"Destroyed class"<<std::endl;
}

//this returns the double free error
/*
myPlan::~myPlan()
{
    for(int i = 0; i < rows; ++i)    
        {
            delete[] cell[i];
        }
        delete[] cell;
}

*/

我知道这是性能方面较慢的解决方案(堆分配)，我尝试使用 std::vector 方式.

I know that this is performance-wise slower solution (heap allocation), I tried to use std::vector way.

非常感谢您的帮助

推荐答案

您的构造函数分配了一个大小为 rows (3) 的顶级数组，然后继续填充 slots(10)元素吧:

Your constructor allocates a top-level array of size rows (3) but then goes on to fill slots (10) elements of it:

cell = new int* [rows]; 

// Create a row for every pointer 
for (int i=0; i<slots; i++) 
{ 
   cell[i] = new int[slots];  
}

由于 cell 仅包含 3 个元素，因此通过写入过去分配的内存来牢固破坏堆后的 7 个分配.如果你在 valgrind 或 Memory sanitizer 下运行你的代码，这个错误应该立即突出.

As cell only holds 3 elements, the 7 allocations after firmly corrupt the heap by writing past allocated memory. If you run your code under valgrind or Memory sanitizer, this error should immediately stand out.

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