Question

I have problems understanding why when I create two or more nodes (as shown below), the function void del_end()will only delete the char name[20] and not the whole node . How do I fix this problem without memory leak?

#include <iostream>
using namespace std;

struct node
{
    char name[20];
    char profession[20];
    int age;
    node *nxt;
    node *prv;
};

node *start_ptr = NULL;

void del_end()
{
    node *temp, *temp2;
    temp = start_ptr;
    if (start_ptr == NULL)
        cout << "Can't delete: there are no nodes" << endl;
    else if (start_ptr != NULL && start_ptr->nxt == NULL)
    {start_ptr=NULL;}
    else
    {
    while (temp->nxt != NULL)
    {
        temp = temp->nxt;
    }
    temp2=temp->prv;
    delete temp;
    temp->nxt= NULL;
    }
}

Answer 1

Your code has some problems, the worst being here:

temp2=temp->prv;
delete temp2;
temp->nxt= NULL;

You’re deleting the next-to-last node, leaving any pointers to it dangling, and losing the last node.

But if you post more of the real code, we can tell you more.

EDIT:
Here’s a slightly cleaned-up version of del_end (and there’s still plenty of room for improvement).

void del_end()
{
  if (start_ptr == NULL)
  {
    cout << "Can't delete: there are no nodes" << endl;
    return;
  }

  if (start_ptr->nxt == NULL)
  {
    delete start_ptr;
    start_ptr = NULL;
    return;
  }

  node *nextToLast = start_ptr;
  node *last = start_ptr->nxt;

  while(last->nxt != NULL)
  {
    nextToLast = last;
    last = last->nxt;
  }

  delete last;
  nextToLast->nxt = NULL;

  return;
}

Note that this does not assume that the prev links are correct, which seems prudent here.