图书馆模拟程序出现Segmentation Fault，无法访问公共变量

我正在编写一个图书馆模拟程序，其中的add函数出现了Segmentation Fault，不清楚故障原因。

函数开头代码：

void add()
{
    Book* newBook = new Book;
    Book* temp = new Book;
    temp = head;
    string tempstring;
    int id;
    int n;

    cout << "Enter the ID of the book you wanna add: ";
    cin >> id;

下方的if条件用于检查链表是否为空，若为空则添加书籍并退出函数：

if(head == NULL)
    {
        newBook->id = id;
        cout << "Enter the name of the Book: ";
        cin >> tempstring;
        newBook->nameOfTheBook = tempstring;
        cout << "Enter the Name of the Author: ";
        cin >> tempstring;
        newBook->author = tempstring;
        cout << "Enter The number of copys you're going to add: ";
        cin >> n;
        newBook->numOfBooks += n;

        newBook->next = NULL;
        head = newBook;
        return;
    }

我的错误出现在if(temp->id == id)这个条件判断处：

if(

    while(temp != NULL)
    {
        if(temp->id == id)
        {
            temp->numOfBooks += 1;
            if(temp->avaliable == 0)
            temp->avaliable = 1;
            return;
        }
        temp = temp->next;
    }
    newBook->id = id;
    cout << "Enter the name of the Book: ";
    cin >> tempstring;
    newBook->nameOfTheBook = tempstring;
    cout << "Enter the Name of the Author: ";
    cin >> tempstring;
    newBook->author = tempstring;
    cout << "Enter The number of copys you're going to add: ";
    cin >> n;
    newBook->numOfBooks += n;

此时temp的值应为NULL，我尝试将temp替换为newBook：

newBook->prev = temp->prev;
    newBook->next = NULL;
    temp->prev->next = newBook;

    newBook->avaliable = 1;   
}

内容的提问来源于stack exchange，提问作者kan3