valgrind在单个链接列表示例中显示内存泄漏

Question

Here is my code.

#include <bits/stdc++.h> 
using namespace std; 

class Node { 
public: 
    int data; 
    Node* next; 
}; 

void printList(Node* n) 
{ 
    while (n != NULL) { 
        cout << n->data << " "; 
        n = n->next; 
    } 
} 

void delete_list(Node *n)
{
    Node *tmp = NULL;
    tmp = new Node();
    while (n != NULL){
        tmp=n->next;
        delete (Node *)n;
        n=tmp;
    }
    delete (Node *)tmp;
}


int main() 
{ 
    Node* head = NULL; 
    Node* second = NULL; 
    Node* third = NULL; 

    head = new Node(); 
    second = new Node(); 
    third = new Node(); 

    head->data = 1; 
    head->next = second;

    second->data = 2;
    second->next = third; 

    third->data = 3;
    third->next = NULL; 

    printList(head); 

    // Delete the entire list
    delete_list(head);

    return 0; 
} 

• HEAP摘要：enter code here退出时使用：1块中的16个字节堆总使用量：6个分配，5个释放，73,792字节分配1块中的16个字节肯定在1的丢失记录中丢失在0x4C3017F：运算符new（unsigned long）（在/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so中）通过0x10895E：delete_list（Node *）（demo.cpp：24）通过0x108A87：主（demo.cpp：58）泄漏摘要：绝对丢失：1个块中的16个字节间接丢失：0字节（0块）可能丢失：0字节（0块）仍可访问：0字节（0块）已抑制：0字节，0块有关检测到和抑制的错误的计数，请重新运行：-v错误摘要：来自1个上下文的1个错误（禁止显示：0至0）

Answer 1

void delete_list(Node *n)
{
    Node *tmp = NULL;

    // this is your memory leak:
    // you just created a new node ...
    tmp = new Node();

    while (n != NULL)
    {
        // ... and very first thing you do is assigning another node to the only
        // pointer holding the node created just before
        tmp = n->next;

        delete (Node *)n;
        n = tmp;
    }

    // apart from cast being obsolete (tmp HAS appropriate type!)
    // tmp is already nullptr and you don't delete anything at all
    delete (Node *)tmp;
}

此示例很好地说明了为什么将变量尽可能地保持局部是一个好主意：

while (n != NULL)
{
    Node* tmp = n->next;
    delete (Node *)n;
    n = tmp;
}

[您根本无法在没有需要的情况下尝试分配任何东西（甚至创建不相关的对象）或试图删除不再存在的东西...

Answer 2

是的，我做了同样的事情。谢谢你们。

void delete_list(Node *n)
{
        Node *tmp = NULL;
//      tmp = new Node();
        while (n != NULL){
        tmp=n->next;
        delete (Node *)n;
        n=tmp;
    }
//    delete (Node *)tmp;
}

现在没有内存泄漏。 :)Memcheck，内存错误检测器版权所有（C）2002-2017，以及Julian Seward等人的GNU GPL。使用Valgrind-3.13.0和LibVEX;使用-h重新运行以获取版权信息命令：./ a.out1 2 3文件描述符：3在出口打开。打开文件描述符2：/ dev / pts / 3打开文件描述符1：/ dev / pts / 3打开文件描述符0：/ dev / pts / 3堆摘要：在出口使用：0字节，0块堆总使用量：5个分配，5个释放，73,776字节分配所有堆块都已释放-不可能泄漏有关检测到和抑制的错误的计数，请重新运行：-v错误摘要：0个上下文中的0个错误（禁止显示：0个中的0个）