Delete last node in linked list

[Beginner of C]

Why am I getting an arbitrary output on the place of the deleted element ? Please help.
Below is the function I wrote
LINKED LIST: 4 3 2
RESULT: 4 3 16608944 NULL

  void delete_last()
    {
        node *tmp = head;
        int count=0;
        while(tmp != NULL){
            if(tmp->next == NULL){
                tail = tmp;
                delete tmp;
                break;
            }
            count++;
            tmp = tmp->next;
        }
    }

Thank you in advance

[keskiverto]

What is the value of member 'next' of the last element after the operation?

[jonnin]

Draw pictures until you get a feel for this stuff.

a list:
1-2-3-4-5-N
H
T
initially, after tmp = head... you  have the above. 
you loop a bit, and eventually tmp->next is null (N)

1-2-3-4-5-N
H       T

so tail = tmp = the 5 in this case. 
delete tmp.   tail and tmp are both now invalid. now what?

then loop ends and tmp = invalid->next.  what?

so what needs to happen?
here,
you need to set 4's next to null.
you need to delete 5.
it needs to work if there are 0, 1, and 2+ items in your list. in these cases you don't have next->next as a way to find the 5 while holding onto the 4. it must handle all these cases!
so what do you do when head == null, or the lists look like these
1 //delete the one and only element and set head to null
1 - 2 //delete the 2 and head-> next is null
1 - 2 - 3 //this is the more normal case that I already said.