c++ - 我很难修复我认为是双重免费的东西

Question

我正在尝试创建一个链表 vector 作为类成员。 Valgrind 显示没有内存泄漏，但也会在程序结束时产生 Invalid free()/delete/delete[]/realloc() 错误。

我试图通过为链表编写析构函数、复制构造函数和复制赋值运算符来解决这个问题。我相信这些已经正确实现。我还尝试了各种向成员 vector 添加链表的方法(引用、指针、智能指针)，但似乎都无法解决问题。

#include "lists.h"

lists::lists() {

}

void lists::newList() {
  int size, value;
  cout << "Please specify size of this list" << endl;
  cin >> size;
  shared_ptr<list> new_list(new list);
  //list *new_list = new list();
  for (int i = 0; i < size; i++) {
    cout << "Enter value for node " << i + 1 << endl;
    cin >> value;
    new_list->pushBack(value);
  }
  list_storage.push_back(new_list);
  //delete new_list;
}

void lists::deleteList() {

}

void lists::display() {
  for (int i = 0; i < list_storage.size(); i++) {
    list_storage[i]->display();
  }
}

#include "list.h"

list::list() {
  head = NULL;
}

list::list(const list& list) {
  head = NULL;
  node *current = head;
  while (current != NULL) {
    this->pushBack(current->data);
    current = current->next;
  }
}

list& list::operator=(const list& rhs) {
  list temp(rhs);
  swap(temp.head, head);
  return *this;
}

list::~list() {
  if (head != NULL) {
    node *current = head;
    while (current != NULL) {
      node *next = current->next;
      delete current;
      current = next;
    }
    delete head;
  }
}

这是 valgrind 的输出:

==15967== Invalid free() / delete / delete[] / realloc()
...
==15967== HEAP SUMMARY:
==15967==     in use at exit: 0 bytes in 0 blocks
==15967==   total heap usage: 9 allocs, 10 frees, 74,856 bytes allocated
==15967== 
==15967== All heap blocks were freed -- no leaks are possible
==15967== 
==15967== For counts of detected and suppressed errors, rerun with: -v
==15967== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

Answer 1

看看你的析构函数:

list::~list() {
  if (head != NULL) {
    node *current = head;
    while (current != NULL) {
      node *next = current->next;
      delete current;
      current = next;
    }
    delete head;
  }
}

进入循环，删除current，这是第一次迭代的head。在循环之后再次删除 head -> double free。