c++ - 尽管有析构函数调用，但内存泄漏

Question

我正在研究一个看起来像这样的 LinkedList 类:

private:
    LL_element* first;
    LL_element* last; 
    int size;
public:
    //constructor
    Linkedlist(): first(NULL), last(NULL), size(0) {}

    //destructor
    ~Linkedlist();

    //adds element at the end of the list.
    void push_back(int value);

    //removes an element at the end of the list.
    bool pop_back(int& value);

函数 push_back 创建一个新的 LL_element 对象(动态分配)。 函数 pop_back 显式删除列表末尾的元素。 只要列表不为空，析构函数就会使用函数 pop_back。 问题是当我创建一个 Linkedlist 对象时:

Linkedlist foo =   Linkedlist();
foo.push_back(3);
foo.push_back(5);

当 foo 超出范围时，调用析构函数，但 Visualstudio 仍然给我 LL_elements 的内存泄漏。但是当我动态分配时:

Linkedlist* foo = new Linkedlist();
foo->push_back(3);
foo->push_back(5);

然后用'delete'调用析构函数，VS不给memoryleaks。

是编译器没有正确调用析构函数还是在堆栈上创建 Linkedlist 时没有正确使用默认构造函数？是真的 把我弄糊涂了……

push_back 和 pop_back 的代码:

bool Linkedlist:: pop_back(int& value) {

//only if the list is not empty, an element can be removed.
if(!this->is_empty()) {

    value = this->last->get_value();
    LL_element* removed = this->last;
    this->last = removed->get_previous();

    if(this->size!=1) {
    this->last->set_next(NULL);
    }

    delete removed; 
    size--;
    return true;
}   

value = 0;
cout << EMPTY_LIST_MESSAGE << endl;
return false;}

void Linkedlist:: push_back(int value)
{

LL_element* to_add = new LL_element(value);

//if there already is a first element, we can ignore it
if(!this->is_empty()) {

    this->last->set_next(to_add);
    to_add->set_previous(last);
    this->last = to_add;
    size++;

}

//if the list is empty --> special case.
else {

    this->first = to_add;
    this->last = to_add;
    size++;

}
}

SSCCE:

int main(int argc, const char * argv[]) {

Linkedlist foo; 
foo.push_back(3);
foo.push_back(5);
foo.push_back(6);
foo.push_back(7); 
_CrtDumpMemoryLeaks();
return 0;
}

输出:

Detected memory leaks!
Dumping objects ->
{139} normal block at 0x00A58148, 12 bytes long.
 Data: <            > 00 00 00 00 00 81 A5 00 07 00 00 00 
{138} normal block at 0x00A58100, 12 bytes long.
 Data: <H           > 48 81 A5 00 B8 80 A5 00 06 00 00 00 
{137} normal block at 0x00A580B8, 12 bytes long.
 Data: <     0      > 00 81 A5 00 F0 30 A5 00 05 00 00 00 
{136} normal block at 0x00A530F0, 12 bytes long.
 Data: <            > B8 80 A5 00 00 00 00 00 03 00 00 00 
Object dump complete.
The program '[5592] linkedlist.exe' has exited with code 0 (0x0).

Answer 1

您正在检查 foo 超出范围之前的内存泄漏，因此它没有机会调用其析构函数，这反过来可能会清除所有 LL_elements(假设，因为您没有发布析构函数代码)。像这样尝试:

int main(int argc, const char * argv[]) {
    {
        Linkedlist foo; 
        foo.push_back(3);
        foo.push_back(5);
        foo.push_back(6);
        foo.push_back(7); 
    }
    _CrtDumpMemoryLeaks();
    return 0;
}