c++ - Segmentation Fault in deleting a node -

i have c++ code manipulates basic linked list - add new node, delete node , view list

//unix environment #include <iostream> #include <malloc.h> #include <stdlib.h> #include <stdio.h> #define clear() printf("\033[h\033[j") using namespace std;  struct node {     int val;     node *next; };  struct node* head = null;  void add_node(struct node *hea) {     char f;     int val;     cout<<"enter value : ";     cin>>val;     if(head==null)     {         head = new(struct node);         head->val = val;         head->next = null;     }     else     {         node *traverser = hea;         node *traverser_prev = null;         while(traverser!=null)         {             traverser_prev = traverser;             traverser=traverser->next;         }         traverser = new(struct node);         traverser->val = val;         traverser->next = null;         traverser_prev->next=traverser;     }     cout<<"\nenter y return : ";     cin>>f;     while(f!='y')     {         cout<<"wrong entry.enter again : ";         cin>>f;     }     return; }  void view_list(struct node *hea) {     char f;     node *traverser = hea;     while(traverser!=null)     {         cout<<traverser->val<<" ";         traverser=traverser->next;     }     cout<<"\nenter y return : ";     cin>>f;     while(f!='y')     {         cout<<"wrong entry.enter again : ";         cin>>f;     }     return; }  void delete_node(node *hea) {     char f;     int del_value;     cout<<"enter value deleted :";     cin>>del_value;      node *traverser = hea;     cout<<"ok1\n";     node* traverser_prev = null;     cout<<"ok2\n";      while(traverser!=null)     {         if(traverser->val==del_value)         {             if(traverser==hea)             {                 hea=traverser->next;                 cout<<"here cond1\n";                 delete traverser;             }             else             {                 traverser_prev->next = traverser->next;                 cout<<"here cond2\n";             }         }         else         {             traverser_prev = traverser;             traverser = traverser->next;             cout<<"here cond3\n";         }     }     cout<<"\nenter y return : ";     cin>>f;     while(f!='y')     {         cout<<"wrong entry.enter again : ";         cin>>f;     }     return; } int main(int argc, char* argv[]) {     while(1)     {         clear();         int choice;         cout<<"pointer basics\n";         cout<<"1. add new element\n";         cout<<"2. view elements\n";         cout<<"3. delete element\n";         cout<<"4. exit\n";         cout<<"enter choice: ";         cin>>choice;         switch(choice)         {             case 1: add_node(head);                     break;             case 2: view_list(head);                     break;             case 3: delete_node(head);                     break;             default:break;         }         if(choice==4)             break;     } } 

however, whenever try delete node, throws me segmentation fault error core dumped. reason error?

one problem in delete_node function pass list head by value, means pointer copied , inside function modify copy.

there 2 solutions: either don't use argument @ , use global variable, or pass argument by reference:

void delete_node(node*& hea)