Segmentation Fault(core dump)

[chaitu21191]

M just a beginner !
The topic name is my issue at runtime !!
here is the code ! its a linked list by the way..

#include<iostream>
using namespace std;

struct structure
{
int value;
struct structure *next;
};
typedef struct structure node;

class linked_list
{
node *head; node *tail;
node *newnode;
public:
linked_list()
{
head = NULL;
tail = NULL;
}
void create(node *newnode);
void deletenode(node *newnode);
void display(node *newnode);
};

void linked_list::create(node *newnode)
{
int x;char place;
if(head==NULL && tail==NULL)
{
cout<<"Enter a number\n";
cin>>x;
newnode->value = x;
newnode->next = NULL;
head = newnode;
tail = newnode;
cout<<"Node Inserted";
}
else
{
cout<<"Enter a number\n";
cin>>x;
cout<<"Enter where do you want to insert... H for Head and T for Tail\n";
cin>>place;
if(place == 'H')
{
newnode->value = x;
newnode->next = head;
newnode = head;
cout<<"Node Inserted";
}
else
{
if(place == 'T')
{
newnode->value = x;
newnode->next = NULL;
tail->next = newnode;
newnode = tail;
cout<<"Node Inserted";
}
else
{
cout<<"please enter a valid place to insert... H for Head and T for Tail\n";
create(newnode);
}
}
}
display(head);
}

void linked_list::deletenode(node *newnode)
{
int x;
node *prev;
head = NULL;
tail = NULL;
cout<<"enter the value you want to delete\n";
cin>>x;
prev = head;
newnode = head->next;
if(head->value == x)
{
head = head->next;
display(head);
}
else
{
if(newnode->value==x)
{
prev->next = newnode->next;
display(head);
}
else
{
newnode = newnode->next;
prev = prev->next;
deletenode(newnode);
}
}
}

void linked_list::display(node *newnode)
{
newnode = head;
cout<<newnode->value;
if(newnode->next == NULL)
{
cout<<".";
}
else
{
cout<<"->";
newnode = newnode->next;
display(newnode);
}
}

int main()
{
int x;
node *newnode;
node *head = NULL;
node *tail = NULL;
linked_list l;
cout<<"1.Insert 2.Delete 3.Display 4.Exit\n";
cout<<"Enter your choice\n";
cin>>x;
switch(x)
{
case 1:
l.create(newnode);
case 2:
l.deletenode(newnode);
case 3:
l.display(newnode);
case 4:
return 0;
}
}

[ne555]

[code] "Please use code tags" [/code]
backtrace

[chaitu21191]

Thanks ..
Here is the code with tag
pl help me out !!
Segmentation fault error at runtime

#include<iostream>
using namespace std;

struct structure
{
    int value;
    struct structure *next;
};
typedef struct structure node;

class linked_list
{
     node *head; node *tail;
     node *newnode;
     public:
          linked_list() 
          {
                head = NULL;
                tail = NULL;
           }
          void create(node *newnode);
          void deletenode(node *newnode);
          void display(node *newnode);
};

void linked_list::create(node *newnode)
{
          int x;char place;
          if(head==NULL && tail==NULL)
          {
               cout<<"Enter a number\n";
               cin>>x;
               newnode->value = x;
               newnode->next = NULL;
               head = newnode;
               tail = newnode;
               cout<<"Node Inserted";
          }
          else
         {
               cout<<"Enter a number\n";
               cin>>x;
               cout<<"Enter where do you want to insert... H for Head and T for Tail\n";
               cin>>place;
               if(place == 'H')
               {
                              newnode->value = x;
                              newnode->next = head;
                              newnode = head;
                              cout<<"Node Inserted";
               }
               else 
               {
                              if(place == 'T')
                              {
                                             newnode->value = x;
                                             newnode->next = NULL;
                                             tail->next = newnode;
                                             newnode = tail;
                                             cout<<"Node Inserted";
                               } 
                              else
                              {
                                             cout<<"please enter a valid place to insert... H for Head and T for Tail\n";
                                             create(newnode);
                              }
               } 
        }
       display(head); 
} 

void linked_list::deletenode(node *newnode)
{
               int x;
               node *prev;
               head = NULL;
               tail = NULL;
               cout<<"enter the value you want to delete\n";
               cin>>x;
               prev = head;
               newnode = head->next;
               if(head->value == x)
               {
                              head = head->next;
                              display(head);
               }
               else
               {
                              if(newnode->value==x)
                              {
                                             prev->next = newnode->next;
                                             display(head);
                              }
                              else
                              {
                                             newnode = newnode->next;
                                             prev = prev->next;
                                             deletenode(newnode);
                              }
               }
}

void linked_list::display(node *newnode)
{
               newnode = head;
               cout<<newnode->value;
               if(newnode->next == NULL)
               {
                              cout<<".";
               }
               else
               { 
                              cout<<"->";
                              newnode = newnode->next;
                              display(newnode);
               }
}

int main()
{
               int x;
               node *newnode;
               node *head = NULL;
               node *tail = NULL;
               inked_list l;
               cout<<"1.Insert 2.Delete 3.Display 4.Exit\n";
               cout<<"Enter your choice\n";
               cin>>x;
               switch(x)
               {
                              case 1:
                                             l.create(newnode);
                              case 2:
                                             l.deletenode(newnode);
                              case 3:
                                             l.display(newnode);
                              case 4:
                                             return 0;
               }
}  

[S G H]

1. You can use the Edit button
2. That indentation... :/
3.

ne555 wrote:

backtrace

4. At which point does it crash?
5. l.create(newnode);
newnode is undefined. you should use new node(); instead, or avoid using pointers while you're learning program basics.

[chaitu21191]

3. Pl help me with backtrace... can i get more info on it !
4.It crashes when i type in a value for insertion/deletion. I think the function call works fine cause the first cout commands are being executed !
5.isnt node *newnode; defining the newnode ?

[S G H]

It's declaring it.
But not defining its content.
Its content is not a regular pointer, it's a random value.
You use new node(); to request a pointer to a node.
But you must delete (newnode); to free it.

Also:
http://www.cplusplus.com/articles/Lw6AC542/

[ne555]

http://ftp.gnu.org/old-gnu/Manuals/gdb-5.1.1/html_node/gdb_42.html

$ g++ main.cpp -ggdb
$ gdb a.out
> run
(Seg fault)
> backtrace
#0  0x0000000000400a00 in linked_list::create (this=0x7fffffffe2c0, newnode=0x4008c0 <_start>) at main.cpp:33
#1  0x0000000000400d4d in main () at main.cpp:132

there you see the exact line where it crashes, /*33*/ newnode->value = x; probably because you never initialized its value

[chaitu21191]

Thanks a lot.
Can you please help me how do i do that ??