读取访问冲突(this->headPtr 0xCDCDCDCD)

Question

Remove （T &item） 应该删除 headPtr 并将该"item 值"存储在 "item" 中并返回 true，否则如果队列中没有元素，则返回 false。 我在此函数中收到"读取访问冲突错误"。以下是类和函数定义：

class SharedQueue {
public:
    SharedQueue();
    ~SharedQueue();
    //Return true if the queue is empty
    bool IsEmpty() const;
    //Enqueue the next item at the tail of the queue.
    void Add(T value);
    //Dequeue the next queue element and store it in "item" variable.  The function returns false if the queue is empty and no item can be retrieved.
    bool Remove(T &item);
    void Print();
private:
    struct QueueItem {
        T item;
        QueueItem *next;
    };
    //Fill in the The private data members.
    QueueItem *headPtr;
    QueueItem *tailPtr;
};
template <typename T> SharedQueue<T>::SharedQueue() {
    headPtr = NULL;
    tailPtr = NULL;
}
template <typename T>SharedQueue<T>::~SharedQueue() {
    QueueItem *temp;
    while (headPtr != NULL) {
        temp = headPtr;
        headPtr = headPtr->next;
        delete temp;
    }
}
template <typename T> bool SharedQueue<T>::IsEmpty() const {
    if (headPtr == NULL && tailPtr == NULL) {
        return true;
    }
    return false;
}
template <typename T> void SharedQueue<T>::Add(T aValue) {
    if (headPtr == NULL) {
        QueueItem *newItem = new QueueItem;
        newItem->item = aValue;
        tailPtr = headPtr = newItem;
    }
    else {
        QueueItem *newItem = new QueueItem;
        newItem->item = aValue;
        tailPtr->next = newItem;
        tailPtr = tailPtr->next;
    }
}
template <typename T> bool SharedQueue<T>::Remove(T &item) {
    if (headPtr == NULL) {
        return false;
    }
    else {
        QueueItem temp = *headPtr;
        item = headPtr->item;
        delete headPtr;
        headPtr = temp.next;
        return true;
    }
}
template <typename T> void SharedQueue<T>::Print() {
    QueueItem *temp = headPtr;
    while (temp != NULL) {
        std::cout << temp->item << "n";
        temp = temp->next;
    }
}

Answer 1

将项目添加到非空SharedQueue<T>时：

    QueueItem *newItem = new QueueItem;
    newItem->item = aValue;
    tailPtr->next = newItem;
    tailPtr = tailPtr->next;

您从未设置newItem->next = NULL 。

您的私有struct QueueItem可以（并且可能应该）拥有自己的构造函数/析构函数，以帮助确保一致地设置此类内容。