CPP- I am getting Segmentation fault (core dumped)?

Question

I am trying to implement a singly linked list.. I am executing the code on terminal and i get the Segmentation fault (core dumped). I dont understand why is it happening? I read the other answers for the same and unfortunately none of them helped..

Any help will be appreciated..Please explain where did it went wrong? Thanks!

 //singly linked list 

#include<iostream>

using namespace std;

class node
{
int data;
node *next;

public:

node()    //constructor
{
    data=0;
    next=NULL;
}

void setdata(int x)
{
    data=x;
}

void setnext(node *x)
{
    next=x;
}

int getdata()
{
    return data;
}
node* getnext()
{
    return next;
}

};

class list
{
node *head;


public:

list()                               // constructor
{
    head=NULL;
}

void firstnode(int x)
{
    node *temp;
    temp=new node;
    temp->setdata(x);
    temp->setnext(head);
    head=temp;
}

void insertbeg(int x)
{

    node *temp1;        
    temp1=new node;                            //Allocate memory to temp1
    temp1->setdata(x);                         // set data  in new node to be inserted
    temp1->setnext(head);          // new node points to previous first node
    head=temp1;                              // head now points to temp1

}

void insertbet(int x,int y)
{
    node *temp1;
    node *temp2;

    temp1=new node;                       // Allocate memory to temp1
    temp2=new node;                        // Allocate memory to temp2

    temp1=head;                           // point temp1 to head so both of them point to first node

    for(int i=0;i<y;i++)                  // To reach the desired node where data is to be inserted
    {
        temp1->getnext();                // point to next of node pointed by temp
        temp1=temp1->getnext();          // temp1 now contains address of node pointed by next
    }

    temp2->setdata(x);
    temp2->setnext(temp1->getnext());         // insert new node in list 
    temp1->setnext(temp2);                  // points the y-1 node to new node

}

void insertend(int x)
{
    node *temp1;
    node *temp2;

    temp1=new node;
    temp2=new node;

    temp1=head;

    while(temp1!=0)
    {
        temp1=temp1->getnext();
    }

    temp2->setdata(x);
    temp1->setnext(temp2);
    temp2->setnext(NULL);

}

void print()
{
    node *temp1;
    temp1=new node;

    temp1=head;

    while(temp1!=0)
    {
        cout<<temp1->getdata()<<endl;;
        temp1=temp1->getnext();
    }
}

};

int main()
{
list l;
l.firstnode(4);
l.insertbeg(3);
l.insertbeg(4);
l.insertbeg(6);
l.insertend(45);
l.insertend(9);
l.insertbet(2,46);
l.print();

return 0;
}

edit:Sorry guys i am new to coding, i am trying to debug with little progress. I already read the question,the answer is too broad, i need something specific to solve the error.

Possible duplicate of [What is a segmentation fault?](http://stackoverflow.com/questions/2346806/what-is-a-segmentation-fault) — Xiobiq, Aug 22 '16 at 09:08
You should try to use a debugger. I'm not trying to be glib, but sincerely you will benefit most from finding such issues yourself. — Paul Rooney, Aug 22 '16 at 09:10
The laymans debugger is `printf`/`cout`. Stick a load of them in the code and see which is the last to be printed. This will point you towards your crash location. — Paul Rooney, Aug 22 '16 at 09:16

score 3 · Accepted Answer · answered Aug 22 '16 at 09:16

That's why there are debug tools like gdb (just google for it ;) ).

This is the backtrace:

#0  0x00000000004009ba in node::setnext (this=0x0, x=0x614cc0) at a.cpp:25
#1  0x0000000000400c18 in list::insertend (this=0x7fffffffdf10, x=45) at a.cpp:109
#2  0x00000000004008df in main () at a.cpp:137

that means in line 137 there is a function call (l.insertend(45)), then in line 109, there is the next function call (temp1->setnext(temp2)) and the segfault occurs on line 25 (next = x). This is because the node is not initialised (temp1 is 0 in line 109).

Your while-loop is the problem, if you change is to something like this:

while (temp1->getnext() != 0)
    temp1 = temp1->getnext();

This will solve your first issue, but you will get another segfault ;) Try to solve it on your own with the tools provided. If you still need help, please leave a comment and I will post the answer.

CPP- I am getting Segmentation fault (core dumped)?

1 Answers1