使用链表实现堆栈时出现分段错误

Question

I am implementing stack using a linked list as it is given to us in college but am not able to remove the segmentation fault as I have not much idea about a segmentation fault. I am putting my code here. please tell my mistake and the reason so that not repeat this mistake again_/_

#include <stdio.h>
#include <stdlib.h>

struct node {   int data;   struct node *next; }; 
struct node *top = NULL;

//push function representation 
void push (int x) {   
    struct node*newnode;
    newnode = (struct node *) malloc (sizeof (struct node));
    newnode->data = x;
    newnode->next = top;
    top = newnode;
}

//traverse function representation
void traverse () 
{
    struct node*temp;
    temp = top;

    if (top == NULL)
    {
      printf ("Stack is empty, please push some element");
    }   
    else
    {
        while (top != NULL)
        {     
          printf ("The element(s) in Stack are %d", temp->data);
          temp = temp->next;
        }
    }
}

//peek function representation 
void peek () 
{   
    if (top == NULL)
    {
      printf ("Stack is empty");
    }   
    else
    {
        printf ("Top element is %d", top->data);
    } 
}

//pop function representation 
void pop ()
{   
    struct node *temp;   temp = top;   
    if (top == NULL)
    {
      printf ("This is underflow condition");
    }   
    else
    {
        printf ("%d", top->data);
        top = top->next;
        free (temp);
    } 
}

void main () 
{
   push (2);
   push (4);
   traverse ();
   peek ();
   pop ();
}

Answer 1

This part of the traverse function is wrong:

  while (top != NULL)  // <---- ups
  {     
    printf ("The element(s) in Stack are %d", temp->data);
    temp = temp->next;
  }

temp will become NULL when you reach the end of the list but since your check is done on top , you'll dereference the NULL and your program will crash.

It shall be:

  while (temp != NULL)  // <---- fixed
  {     
    printf ("The element(s) in Stack are %d", temp->data);
    temp = temp->next;
  }