[英]In what cases the virtual base destructor can still go uncalled causing memory leaks?
具有基类Heap
和两个派生类MinHeap
和MaxHeap
如下所示:
我将派生类对象创建为:
MinHeap* myminheap = new MinHeap();
但是使用删除它
delete myminheap;
有/没有virtual ~Heap() {}
给我glibc内存泄漏错误! 症结是什么? 我已经在此发表了很多文章.....
....但我无法弄清楚为什么设置基本析构函数虚拟仍然会导致内存错误?
Heap* h_ptr = myminheap;
delete h_ptr;
ps。 不能做^事情,因为以下错误弹出,所以我无法将派生类对象指针转换为基本指针
‘class Heap’ has no member named ‘insert’
‘class Heap’ has no member named ‘pop_min'
我可以通过在Heap
类中介绍它们来照顾自己
后来,我意识到, delete h_ptr;
调用delete h_ptr;
如直接delete h_ptr;
如果我打电话给free(h_ptr);
我没有受到内存泄漏的影响..万岁! 但是我需要对此行为有一些了解!
堆
#include <cstdlib>
#include <vector>
#include <iterator>
using namespace std;
class Heap
{
public:
Heap() {}
~Heap() {}
vector <int> heap;
int left(int parent);
int right(int parent);
int parent(int child);
int size() {return heap.size();}
virtual void insert(int element) {}
virtual int pop_min() {}
virtual int pop_max() {}
void print();
};
class MinHeap : public Heap
{
private:
void heapify_up(int index);
void heapify_down(int index);
public:
MinHeap() {}
~MinHeap() {}
int pop_min();
void insert(int element);
};
class MaxHeap : public Heap
{
private:
void heapify_up(int index);
void heapify_down(int index);
public:
MaxHeap() {}
~MaxHeap() {}
int pop_max();
void insert(int element);
};
堆
#include <cstdlib>
#include <iostream>
#include <vector>
#include <iterator>
using namespace std;
#include "heap.h"
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
int Heap::left(int parent)
{
int i = (parent << 1) + 1; //2 * parent + 1 read more on bit shifts
return (i < heap.size()) ? i : -1;
}
int Heap::right(int parent)
{
int i = (parent << 1) + 2;
return (i < heap.size()) ? i : -1;
}
int Heap::parent(int child)
{
if(child){
int i = (child >> 1) - 1;
return i;
}
else return -1;
}
void Heap::print()
{
vector<int>::iterator i = heap.begin();
cout << "Heap = ";
while(i != heap.end()){
cout << *i << " ";
i++;
}
cout << endl;
}
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
int MinHeap::pop_min()
{
int min = heap.front();
heap[0] = heap[heap.size() - 1];
heap.pop_back();
heapify_down(0);
return min;
}
void MinHeap::insert(int element)
{
heap.push_back(element);
heapify_up(heap.size() - 1);
}
void MinHeap::heapify_up(int index)
{
while(index > 0 && parent(index) >= 0 && heap[parent(index)] > heap[index]){
int temp = heap[index];
heap[index] = heap[parent(index)];
heap[parent(index)] = temp;
index = parent(index);
}
}
void MinHeap::heapify_down(int index)
{
int child = left(index);
if(child > 0 && right(index) > 0 && heap[child] > heap[right(index)])
child = right(index);
if(heap[index] > heap[child]){
int temp = heap[child];
heap[child] = heap[index];
heap[index] = temp;
heapify_down(child);
}
}
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
int MaxHeap::pop_max()
{
int max = heap.front();
heap[0] = heap[heap.size() - 1];
heap.pop_back();
heapify_down(0);
return max;
}
void MaxHeap::insert(int element)
{
heap.push_back(element);
heapify_up(heap.size() - 1);
}
void MaxHeap::heapify_up(int index)
{
while(index > 0 && parent(index) >= 0 && heap[parent(index)] < heap[index]){
int temp = heap[index];
heap[index] = heap[parent(index)];
heap[parent(index)] = temp;
index = parent(index);
}
}
void MaxHeap::heapify_down(int index)
{
int child = left(index);
if(child > 0 && right(index) > 0 && child < right(index))
child = right(index);
if(heap[index] < heap[child]){
int temp = heap[child];
heap[child] = heap[index];
heap[child] = temp;
heapify_down(child);
}
}
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// test program
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
int main(){
// Create the heap
MinHeap* myminheap = new MinHeap();
myminheap->insert(700);
myminheap->print();
myminheap->insert(500);
myminheap->print();
myminheap->insert(100);
myminheap->print();
myminheap->insert(800);
myminheap->print();
myminheap->insert(200);
myminheap->print();
myminheap->insert(400);
myminheap->print();
myminheap->insert(900);
myminheap->print();
myminheap->insert(1000);
myminheap->print();
myminheap->insert(300);
myminheap->print();
myminheap->insert(600);
myminheap->print();
// Get priority element from the heap
int heapSize = myminheap->size();
for ( int i = 0; i < heapSize; i++ )
cout << "Get min element = " << myminheap->pop_min() << endl;
// Cleanup
delete myminheap;
return 1;
}
如果您新建了MinHeap,则无法通过在Heap类型上调用free来删除它。 您的问题是,您正在存储指向该对象的指针,并说这是另一回事,结果,删除例程不知道您要删除MinHeap,而仅删除(大致)了Heap部分。
您可以直接在myminheap对象上调用delete,这应该可以工作。
更好的解决方案是根本不在堆上创建MinHeap,在堆栈上创建它并在没有任何指针的情况下使用它。 如果由于某种原因需要在堆上创建它,请改为在智能指针类中创建它,例如,使用shared_ptr <>可以极大地帮助您。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.