There is a segmentation fault in the remove function of this doubly linked list. Debugging with gdb in the linux terminal shows that
1) Only the first condition, if(curr->prev == NULL), where the node to delete is the first node in the list is ever reached.
2) On the command delete curr, the program steps into the destructor for the class that models the data object, and breaks on the command delete title.
Edit:
After implementing user6545984 answer, the only issue is a segementation fault on tail = tail->prev in the else if(curr->next == NULL) condition.
The program is unable to get past this conditional statement.
Also, additional code has been added below. I apologize for the length.
Code for the add and remove functions, as well as the for the destructor:
Add Function (creates doubly linked list)
void SongList::addSongSorted(const Song &aSong)
{
char title[MAX_CHAR];
char currTitle[MAX_CHAR];
aSong.getTitle(title);
Node * newNode = new Node(aSong);
Node * prev = NULL;
Node * curr = head;
while(curr)
{
curr->song.getTitle(currTitle);
if(strcmp(title, currTitle) < 0)
break;
prev = curr;
curr = curr->next;
}
newNode->next = curr;
newNode->prev = prev; //Added due to answer. See edit note.
if(!prev)
head = newNode;
else
{
prev->next = newNode;
}
size++;
}
Remove function
void SongList::remove(const Song& aSong)
{
Node *curr = head;
int indexRem = 0;
int j = 0;
//get the index to remove
cout << "Enter the index to remove.\n";
cout << "This value can be obtained via the list all functionality.\n";
cin >> indexRem;
while(indexRem > getSize()|| indexRem < 0)
{
cout << "Enter a valid index to remove.\n";
cin >> indexRem;
}
while(curr && j < indexRem)
{
curr=curr->next;
j++;
}
if(!curr)
{
cout << "didnt find anything" << endl;
}
else
{
if(curr->prev == NULL) //NOTE: this is the only condition ever engaged
{
head = head->next;
head->prev = NULL;
delete curr; //NOTE: goes to destructor
curr = NULL;
}
else if(curr->next == NULL)
{
tail = tail->prev; //EDIT: only issue is seg fault here
tail->next = NULL;
delete curr;
curr = NULL;
}
else
{
Node * previous = curr->prev;
Node * following = curr->next;
previous->next = following;
following->prev = previous;
delete curr;
}
}
Destructor (please now ignore)
Song::~Song()
{
if(title != NULL)
delete [] title; //Breaks here
if(artist != NULL)
delete [] artist;
if(album != NULL)
delete [] album;
}
Header file for object class
#ifndef SONG_H
#define SONG_H
#include<cstring>
#include<stdio.h>
#include<cstdlib>
const int MAX_CHAR = 101;
const int SONG_CAPACITY = 100;
class Song
{
public:
//constructors
Song();
Song(const char title[], const char artist[], const char album[], int min, int sec);
//Destructor
~Song();
//accessor functions
void getTitle(char title[]) const;
void getArtist(char artist[]) const;
void getAlbum(char album[]) const;
int getMin()const;
int getSec()const;
void print() const;
//mutator functions
void setTitle(const char title[]);
void setArtist(const char artist[]);
void setAlbum(const char album[]);
void setMin(int &min);
void setSec(int &sec);
private:
char* title;
char* artist;
char* album;
int min;
int sec;
};
#endif
Source file for object class
#include "song.h"
#include <iostream>
using namespace std;
Song::Song()
{
title = new char[strlen("no title")+1];
strcpy(title, "no title");
artist = new char[strlen("no artist")+1];
strcpy(artist, "no artist");
album = new char[strlen("no album")+1];
strcpy(album, "no album");
min = 0;
sec = 0;
}
Song::Song(const char title[], const char artist[], const char album[], int min, int sec)
{
this->title = new char[strlen(title)+1];
strcpy(this->title, title);
this->artist = new char[strlen(artist)+1];
strcpy(this->artist, artist);
this->album = new char[strlen(album)+1];
strcpy(this->album, album);
this->min = min;
this->sec = sec;
}
Song::~Song()
{
if(title != NULL)
delete [] title;
if(artist != NULL)
delete [] artist;
if(album != NULL)
delete [] album;
}
void Song::getTitle(char title[]) const
{
strcpy(title, this->title);
}
void Song::getArtist(char artist[]) const
{
strcpy(artist, this->artist);
}
void Song::getAlbum(char album[]) const
{
strcpy(album, this->album);
}
int Song::getMin()const
{
return min;
}
int Song::getSec()const
{
return sec;
}
void Song::print() const
{
cout << title << '\t'
<< artist << '\t'
<< album << '\t'
<< min << '\t'
<< sec << endl;
}
void Song::setTitle(const char title[])
{
if(this->title != NULL)
delete [] this->title;
this->title = new char[strlen(title)+1];
strcpy(this->title, title);
}
void Song::setArtist(const char artist[])
{
if(this->artist != NULL)
delete [] this->artist;
this->artist = new char[strlen(artist)+1];
strcpy(this->artist, artist);
}
void Song::setAlbum(const char album[])
{
if(this->album != NULL)
delete [] this->album;
this->album = new char[strlen(album)+1];
strcpy(this->album, album);
}
void Song::setMin(int &min)
{
this->min = min;
}
void Song::setSec(int &sec)
{
this->sec = sec;
}
###Header file for object management class
#ifndef SONG_LIST
#define SONG_LIST
#include "song.h"
#include <iostream>
using namespace std;
class SongList
{
public:
SongList();
SongList(const char fileName[]);
~SongList();
bool get(int index, Song& aSong) const;
//Search function declaration
void searchArtist(const char artist[], Song& match) const;
void searchAlbum(const char album[], Song& match) const;
int getSize() const;
void printAll() const;
void saveToFile(const char fileName[]) const;
void addSong(const Song& aSong);
// void addAtStart(const Song& aSong);
// void append(const Song& aSong);
void addSongSorted(const Song& aSong);
void loadFromFile(const char fileName[]);
void remove(const Song& aSong);
private:
struct Node
{
Song song;
Node * next;
Node * prev;
Node(const Song& aSong)
{
char title[MAX_CHAR];
char artist[MAX_CHAR];
char album[MAX_CHAR];
int min;
int sec;
aSong.getTitle(title);
aSong.getArtist(artist);
aSong.getAlbum(album);
min = aSong.getMin();
sec = aSong.getSec();
song.setTitle(title);
song.setArtist(artist);
song.setAlbum(album);
song.setMin(min);
song.setSec(sec);
next = NULL;
}
};
Node * head;
Node * tail;
int size;
};
#endif
###Source file for object management class
#include "songlist.h"
#include <iostream>
#include <fstream>
#include <iomanip>
#include <cstring>
using namespace std;
//Ok as is
SongList::SongList()
{
head = NULL;
tail = NULL;
size = 0;
}
//OK as is
SongList::SongList(const char fileName[])
{
head = NULL;
tail = NULL;
size = 0;
loadFromFile(fileName);
}
//Needs modification to deconstruct tail...
SongList::~SongList()
{
Node * curr = head;
while(head != NULL)
{
curr = head->next;
delete head;
head = curr;
}
}
//OK as is
void SongList::loadFromFile(const char fileName[])
{
ifstream in;
char title[MAX_CHAR];
char artist[MAX_CHAR];
char album[MAX_CHAR];
int min;
int sec;
Song aSong;
in.open (fileName);
if(!in)
{
in.clear();
cerr << endl << "Fail to open "
<< fileName << " for input!" << endl << endl;
exit(1);
}
//cout << "loading point reached" << endl;
in.getline(title, MAX_CHAR, ';');
while (!in.eof())
{
//cout << "check input from file" << endl;
in.getline(artist, MAX_CHAR, ';');
in.getline(album, MAX_CHAR, ';');
in >> min;
in.ignore(MAX_CHAR, ';');
in >> sec;
in.ignore(MAX_CHAR, '\n');
aSong.setTitle(title);
aSong.setArtist(artist);
aSong.setAlbum(album);
aSong.setMin(min);
aSong.setSec(sec);
addSong(aSong);
// aSong.print();
in.getline(title, MAX_CHAR, ';');
}
in.close();
}
//Ok as is
int SongList::getSize()const
{
return size;
}
bool SongList::get(int index, Song &aSong) const
{
char title[MAX_CHAR];
char artist[MAX_CHAR];
char album[MAX_CHAR];
int min;
int sec;
if(index < 0 || index >= size)
return false;
int i;
Node * curr = head;
for(i = 0; i < index; i++)
{
curr = curr->next;
}
curr->song.getTitle(title);
curr->song.getArtist(artist);
curr->song.getAlbum(album);
curr->song.getMin();
curr->song.getSec();
aSong.setTitle(title);
aSong.setArtist(artist);
aSong.setAlbum(album);
aSong.setMin(min);
aSong.setSec(sec);
return true;
}
//OK as is
void SongList::searchArtist(const char artist[], Song& match) const
{
Node * curr;
char currentTitle[MAX_CHAR];
char currentArtist[MAX_CHAR];
char currentAlbum[MAX_CHAR];
int currentMin;
int currentSec;
for(curr = head; curr != NULL; curr = curr->next)
{
curr->song.getTitle(currentTitle);
curr->song.getArtist(currentArtist);
curr->song.getAlbum(currentAlbum);
curr->song.getMin();
curr->song.getSec();
if(strcmp(artist, currentArtist) == 0)
{
cout << "Found: " << currentTitle << '\t'
<< currentArtist << '\t'
<< currentAlbum << '\t'
<< currentMin << ':'
<< currentSec << endl;
}
}
}
//Ok as is
void SongList::searchAlbum(const char album[], Song &match) const
{
Node * curr;
char currentTitle[MAX_CHAR];
char currentArtist[MAX_CHAR];
char currentAlbum[MAX_CHAR];
int currentMin;
int currentSec;
for(curr = head; curr != NULL; curr = curr->next)
{
curr->song.getTitle(currentTitle);
curr->song.getArtist(currentArtist);
curr->song.getAlbum(currentAlbum);
curr->song.getMin();
curr->song.getSec();
if(strcmp(album, currentAlbum) == 0)
{
cout << "Found: " << currentTitle << '\t'
<< currentArtist << '\t'
<< currentAlbum << '\t'
<< currentMin << ':'
<< currentSec << endl;
}
}
}
//OK as is
void SongList::printAll() const
{
Node * curr;
char title[MAX_CHAR];
char artist[MAX_CHAR];
char album[MAX_CHAR];
int min;
int sec;
int index = 0;
for(curr = head; curr != NULL; curr = curr->next)
{
curr->song.getTitle(title);
curr->song.getArtist(artist);
curr->song.getAlbum(album);
min = curr->song.getMin();
sec = curr->song.getSec();
cout << index << " " << title << " "
<< artist << " " << album << " "
<< min << ':' << sec << endl;
index++;
}
}
//OK as is
void SongList::saveToFile(const char fileName[])const
{
ofstream out;
Node* curr;
char title[MAX_CHAR];
char artist[MAX_CHAR];
char album[MAX_CHAR];
int min = 0;
int sec = 0;
out.open(fileName);
if(!out)
{
out.clear();
cerr << endl << "Fail to open" << fileName << ". Check your directory." << endl << endl;
exit(1);
}
for(curr = head; curr; curr = curr->next)
{
curr->song.getTitle(title);
curr->song.getArtist(artist);
curr->song.getAlbum(album);
min = curr->song.getMin();
sec = curr->song.getSec();
out << title << ';' << artist << ';' << album << ';' << min << ';' << sec << endl;
}
out.close();
}
void SongList::addSong(const Song &aSong)
{
addSongSorted(aSong);
}
//Don't think I need this
/*
void SongList::addAtStart(const Song &aSong)
{
Node * newNode = new Node(aSong);
newNode->next = head;
head = newNode;
size++;
}
//...or this
void SongList::append(const Song &aSong)
{
Node * newNode = new Node(aSong);
if(!head)
head = newNode;
else
{
Node * curr = head;
while(curr->next)
{
curr = curr->next;
}
curr->next = newNode;
}
size++;
}
*/
void SongList::addSongSorted(const Song &aSong)
{
char title[MAX_CHAR];
char currTitle[MAX_CHAR];
aSong.getTitle(title);
Node * newNode = new Node(aSong);
Node * prev = NULL;
Node * curr = head;
while(curr)
{
curr->song.getTitle(currTitle);
if(strcmp(title, currTitle) < 0)
break;
prev = curr;
curr = curr->next;
}
newNode->next = curr;
newNode->prev = prev;
if(!prev)
head = newNode;
else
{
prev->next = newNode;
}
// printAll();
size++;
}
void SongList::remove(const Song& aSong)
{
Node *curr = head;
int indexRem = 0;
int j = 0;
cout << "Enter the index to remove.\n";
cout << "This value can be obtained via the list all functionality.\n";
cin >> indexRem;
while(indexRem > getSize()|| indexRem < 0)
{
cout << "Enter a valid index to remove.\n";
cin >> indexRem;
}
while(curr && j < indexRem)
{
curr=curr->next;
j++;
}
if(!curr)
{
cout << "didnt find anything" << endl;
}
else
{
if(curr->prev == NULL)
{
head = head->next;
head->prev = NULL;
delete curr;
curr = NULL;
}
else if(curr->next == NULL)
{
tail = tail->prev;
tail->next = NULL;
delete curr;
curr = NULL;
}
else
{
Node * previous = curr->prev;
Node * following = curr->next;
previous->next = following;
following->prev = previous;
delete curr;
}
}
size--;
}
Any suggestions?
