Question

How come void del_begin() crashes when there’s only one node left (I have other functions to add nodes)?

 #include <iostream>
 using namesspace std;

 node *start_ptr = NULL;
 node *current;
 int option = 0;
 void del_end()
 {
     node *temp, *temp2;
     temp = start_ptr;
     if (start_ptr == NULL)
         cout << "There are no nodes" << endl;
     else
     {
         while (temp->nxt != NULL)
         {
            temp2 = temp;
            temp = temp->nxt;
         }
         delete temp;
         temp2->nxt = NULL;
     }
 }
 void display()
 {
     node *temp;
     temp = start_ptr;
     cout << endl;
     if (temp == NULL)
         cout << "There are no nodes to display" << endl;
     else
     {
         while(temp != NULL)
         {
        cout << temp->name << ", " << temp->profession << ", " << temp->age;
        if (temp == current)
            cout << "***";
        cout << endl;
        temp = temp->nxt;
        }
        cout << endl;
     }
 }

 int main()
 {
     start_ptr = NULL;
     int option;
      do
     {
         display();
         cout << "0 for EXIT" << endl;
         cout << "1 to ADD TO END" << endl;
         cout << "2 to ADD TO BEGINNING" << endl;
         cout << "3 to DELETE LAST" << endl;
         cout << "4 to DELETE BEGINNING" << endl;
         cout << ">>";
         cin >> option;
         switch (option)
         {
         case 1 : add_end(); break;
         case 2 : add_begin(); break;
         case 3 : del_end(); break;
         case 4 : del_begin(); break;
         }
     }
     while (option != 0);
     return 0;
 }

Answer 1

You didn’t show us the code for del_begin(), but your del_end() has a bug in the case you’re mentioning (single node list).

If you have only one node, your while loop will never execute, and temp2 will be uninitialized when you get to the line:

 temp2->nxt = NULL;

Crash!