例外がスローされたエラー

Question

私は例外がどこにあるのか把握しようとしており、私のプログラムではそれを実際に把握できません。プログラムリストが行うことは、ノードを見つけて削除することです。ここに私のヘッダファイルです：

#ifndef DOUBLYLIST_H 
#define DOUBLYLIST_H 

#include <string> 
#include <iostream> 
using namespace std; 

class Node 
{ 
public: 
    Node() : data(0), previousLink(NULL), nextLink(NULL) {} 
    Node (int theData, Node *previous, Node *next) 
      : data(theData), previousLink(previous), nextLink(next){} 
    Node *getNextLink() const { return nextLink; } 
    Node *getPreviousLink() const { return previousLink; } 
    int getData() const { return data; } 
    void setData(int theData) { data = theData; } 
    void setNextLink(Node *newNext) { nextLink = newNext; } 
    void setPreviousLink(Node *newPrev) { previousLink = newPrev; } 
    ~Node(){} 
private: 
    int data; 
    Node *nextLink; 
    Node *previousLink; 
}; 


class DoublyList 
{ 
public: 
DoublyList(); 

void insertBack(int newData); 
bool search(int searchData) const; 
void deleteNode(int deleteData);  
void print() const; 
void reversePrint() const; 

void destroyList(); 
~DoublyList(); 

private: 
    Node *first; // pointer to the first node on the list 
    Node *last;  // pointer to the last node on the list 
    int count;  // number of nodes in the list 
}; 
#endif 

そして、ここでのcppファイルです：destroyListで

/* 
    Huynh, Dex 
    CS A250 
    October 9, 2016 

    Lab - 7 Dll Error 
*/ 
#include "DoublyList.h" 

DoublyList::DoublyList() 
{ 
    first = NULL; 
    last = NULL; 
    count = 0; 
} 

DoublyList::~DoublyList() 
{ 
    destroyList(); 
} 

void DoublyList::insertBack(int newData) 
{ 
    Node *newNode = new Node(newData, last, NULL); 

    if (first == nullptr) 
     first = newNode; 
    else 
    { 
     last->setNextLink(newNode); 
     newNode->setPreviousLink(last); 
    } 
} 

bool DoublyList::search(int searchData) const 
{ 
    Node *current = first; 

    while (first != nullptr)  
    {  
     if (current->getData() == searchData) 
      return true; 
     else 
      current = current->getNextLink(); 
    } 
} 

void DoublyList::deleteNode(int deleteData) 
{ 
    if (first == nullptr)  
    { 
     cerr << "Cannot delete from an empty list." << endl; 
    } 
    else 
    { 
     Node *current;  

     if (first->getData() == deleteData) 
     { 
      current = first;     
      first = first->getNextLink(); 

      if (first == NULL) 
       last = NULL;     

      delete current; 
      current = NULL;  
     } 
     else 
     { 
      bool found = false;        
      current = first;  

      while (current != NULL || !found) 
      {     
       if (current->getData() == deleteData) 
        found = true;      
       else 
        current = current->getNextLink(); 
      } 

      if (current == NULL)  
       cerr << "The item to be deleted is not in the list." << endl; 
      else   
      { 
       if (current != last)   
        current->getPreviousLink()->setNextLink(current->getNextLink()); 
       else 
        last = current->getPreviousLink();   

       --count; 
       delete current; 
       current = NULL; 
      } 
     } 
    } 
} 

void DoublyList::print() const 
{ 
    if (first == nullptr) 
     cerr << "List is empty. Cannot print." << endl; 
    else 
    { 
     Node *temp = first; 

     while (temp != NULL) 
     { 
      cout << temp->getData() << " "; 
      temp = temp->getNextLink(); 
     } 
     cout << endl; 
    } 
} 

void DoublyList::reversePrint() const 
{ 
    if (first == nullptr) 
     cerr << "List is empty. Cannot print." << endl; 
    else 
    { 
     Node *temp = last; 

     while (temp != NULL) 
     { 
      cout << temp->getData() << " "; 
      temp = temp->getPreviousLink(); 
     } 
     cout << endl; 
    } 
} 

void DoublyList::destroyList() 
{ 
    Node *temp; 

    while (first != NULL) 
    { 
     first = temp; 
     temp = temp->getNextLink(); 
     delete first; 
     first = NULL; 
    } 

    last = NULL;  
    count = 0; 
} 

Answer 1

Node *temp; 
... 
temp = temp->getNextLink(); 

は、このコードは初期化されていない値を使用しています。プログラムの動作は未定義です。