在另一个 class 中完成删除时出现 Valgrind 错误

Question

我正在尝试在对象局部性较低时测试 C++ 性能，因此我正在尝试分配具有许多 "dead objects" 的大量内存。当它们之间有很多 "dead ones" 时，我将对 "live objects" 进行基准测试。

为此，我定义了一个简单的链表：

#include "LinkedList.hpp"
#include <iostream>
#include <string>

LinkedList::LinkedList() {
    this->first = NULL;
    this->last = NULL;
    this->size = 0;
}

void LinkedList::add(node_t *node) {
    if (!last) {
        first = node;
        last = first;
        size++;
        return;
    }
    last->next = node;
    last = last->next;
    size++;
}


void LinkedList::deleteFirst() {
    if (first == NULL || size <= 0) {
        std::cout << "Cannot Delete from empty list" << std::endl;
        return;
    }
    node_t* oldfirst = first;
    first = first->next;
    delete oldfirst;
    size--;
}

头文件：

#ifndef LINKEDLIST_HPP
#define LINKEDLIST_HPP

class node_t {
    public:
        node_t *next;
};


class LinkedList {

    public:
        LinkedList();
        void add(node_t*);
        void deleteFirst();
        node_t *first;
        int size;
    private:
        node_t *last;
};

#endif

在尝试实验时，我注意到 valgrind 显示我有一些内存泄漏。我很确定我正在删除每个分配的对象。这是我的主要内容：

#include "LinkedList.hpp"
#include <ctime>
#include <cstdlib>

bool doConnect() {
    int  r;
    r = rand();

    return ((r % 2) == 1);
}

int main() {

    srand(time(NULL));
    int size = 100000;
    int i = 0;
    LinkedList *node_list = new LinkedList();
    LinkedList *dead_node_list = new LinkedList();


    for (i=0; i < size; i++) {
        node_t *new_node = new node_t();
        if (doConnect()) {
            node_list->add(new_node);
        }
        else {
            dead_node_list->add(new_node);
        }
    }


    for (i=0; i < dead_node_list->getSize(); i++)
            dead_node_list->deleteFirst();

    for (i=0; i < node_list->getSize(); i++)
            node_list->deleteFirst();

    delete node_list;
    delete dead_node_list;



    return 0;
}

这是 valgrind 的输出：

==15291== Memcheck, a memory error detector
==15291== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==15291== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==15291== Command: ./main
==15291== 
==15291== 
==15291== HEAP SUMMARY:
==15291==     in use at exit: 199,720 bytes in 24,965 blocks
==15291==   total heap usage: 100,002 allocs, 75,037 frees, 800,048 bytes allocated
==15291== 
==15291== LEAK SUMMARY:
==15291==    definitely lost: 16 bytes in 2 blocks
==15291==    indirectly lost: 199,704 bytes in 24,963 blocks
==15291==      possibly lost: 0 bytes in 0 blocks
==15291==    still reachable: 0 bytes in 0 blocks
==15291==         suppressed: 0 bytes in 0 blocks
==15291== Rerun with --leak-check=full to see details of leaked memory
==15291== 
==15291== For counts of detected and suppressed errors, rerun with: -v
==15291== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

我是不是遗漏了什么明显的东西？

我编译我的代码：g++ -Wall -g LinkedList.cpp main.cpp -o main

Answer 1

您认为变量 i 在此代码中的作用是什么？

for (i=0; i < dead_node_list->getSize(); i++)
        dead_node_list->deleteFirst();

大小应该会下降，所以随着 i 的增加，你只删除了一半的原始节点。

你没有给出所有的代码，所以我不得不假设缺少的部分是普通的。但是有了这个假设，上面的代码应该是：

while ( dead_node_list->getSize())
        dead_node_list->deleteFirst();

与其他列表类似。

在另一个 class 中完成删除时出现 Valgrind 错误

Valgrind errors when delete is done in another class

c++

memory-leaks

valgrind

new-operator

delete-operator