segmentation fault in c

Question

1.00/5 (1 vote)

See more:

in this program i have segmentation fault error any one point-out where i was mistake in memory allocation in this program.

C#

//stack program
#include<stdio.h>
#include<conio.h>

struct node
{
       int data;
       struct node *next;   //this variable is refer the same structure
}*top=NULL;
int main()
{
//     clrscr();
     insert(34);   //insert node
     insert(20);

     display();
//     getch();
     return 0;
}
     // insert new stack value
insert(int val)
     {
                struct node *temp = (struct node *)malloc(sizeof(struct node));
                temp = top;
                temp->data = val;
                temp->next = top;
                top = temp;
                }
     //display the stack
display()
     {
              struct node *temp = top;
              while(temp)
              {
                         printf("%d",temp->data);
                         temp = temp->next;
                         }
                         }

Posted 11-Oct-11 5:08am

kschandru

Add a Solution

3 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Manfred Rudolf Bihy · Accepted Answer · 2011-10-11T05:21:00

In the beginning you initialize a pointer to a node variable called top to null.
Then in your insert method you initialize variable temp ( a pointer to a node ) with the pointer you got from allocating an appropriate sized memory chunk. Directly after that you overwrite that temp variable with the content of variable top (which is still null). After this you try to access elements within the node struct.

This explains your pains.

All you have to do is leave that statement out all together:

C#

insert(int val)
{
    struct node *temp = (struct node *)malloc(sizeof(struct node));
    // temp = top; // This is not needed as it overwrites the previously acquired pointer
    temp->data = val;
    temp->next = top;
    top = temp;
}

Best Regards,

—MRB

Albert Holguin · Accepted Answer · 2011-10-11T05:20:00

Solution 1

Why are you assigning top to temp right after you've just allocated temp? Off the back, you're loading NULL where you actually already had a valid heap memory address.

edit:
Also noticed in your small program you never deallocate the memory. You should probably do that unless you want memory leaks.

Posted 11-Oct-11 5:20am

Albert Holguin

Updated 11-Oct-11 7:20am

v2

Comments

Manfred Rudolf Bihy 11-Oct-11 11:24am

Correct! 5+

Albert Holguin 11-Oct-11 11:27am

thank you manfred... looks like a few of us answered almost at the same time...

Manfred Rudolf Bihy 11-Oct-11 11:29am

It was close enough to recognize that! :)

Chuck O'Toole · Accepted Answer · 2011-10-11T05:21:00

Solution 2

C#

struct node *temp = (struct node *)malloc(sizeof(struct node));
temp = top;

So you allocate this new shiny chunk of memory and store it's address in 'temp'

Then you immediately wipe out the pointer with 'top', which is initialized to NULL.

BOOM

Posted 11-Oct-11 5:21am

Chuck O'Toole

Comments

Manfred Rudolf Bihy 11-Oct-11 11:24am

Spot on! 5+