c++ - 我找不到 valgrind 告诉我的内存链接

Question

我正在编写一个链表和一个向其中添加新值的函数，这是我的代码:

    #include <iostream>

    using namespace std;

    struct ListNode {
        int m_value;
        ListNode *m_next;
        ListNode () {}
        ListNode(int i) {
            m_value = i;
            m_next = NULL;
        }
    };

    void append(int const value, ListNode *head) {
        ListNode *list = new ListNode(value);
        if (head != NULL) {
            while (head->m_next != NULL) {
                head = head->m_next;
            }
            head->m_next = list;
        } else {
            head = list;
        }
    }

    void print(ListNode *head) {
        while (head != NULL) {
            cout << head->m_value << endl;
            head = head->m_next;
        }
    }

    int main() {
        ListNode *list = new ListNode(1);
        append(2, list);
        append(3, list);
        append(4, list);
        append(5, list);

        print(list);

        delete list;
}

然后我使用 valgrind 检查内存泄漏，使用这个命令:

    valgrind --leak-check=full --show-reachable=yes --trace-children=yes ./listnodes 

显示:

  64 (16 direct, 48 indirect) bytes in 1 blocks are definitely lost in loss record 4 of 4
  at 0x4C3017F: operator new(unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
  by 0x108B1D: append(int, ListNode*) (in /home/qihao/c/test/listnodes/listnodes/listnodes)
  by 0x108968: main (in /home/qihao/c/test/listnodes/listnodes/listnodes)

  LEAK SUMMARY:
  definitely lost: 16 bytes in 1 blocks
  indirectly lost: 48 bytes in 3 blocks
  possibly lost: 0 bytes in 0 blocks
  still reachable: 0 bytes in 0 blocks
  suppressed: 0 bytes in 0 blocks

  ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

有一处泄漏。我不知道我的代码中发生泄漏的地方，有人可以帮忙吗？谢谢。

Answer 1

因为您只删除了列表的头部。每次调用 append 函数时，您都会创建一个新节点。在你的程序结束时，你必须删除所有节点，尝试做这样的事情:

int main()
{
    ListNode *list = new ListNode(1);
    append(2, list);
    append(3, list);
    append(4, list);
    append(5, list);

    print(list);

    ListNode *tmp1 = list;
    ListNode *tmp2;
    while (tmp1 != NULL)
    {
        tmp2 = tmp1->m_next;
        delete tmp1;
        tmp1 = tmp2;
    }
}