Having trouble deleting elements in doubly linked list - c

Question

I've been trying for about 5 hours to get this code to work properly, and the code is written based on hours of internet research.
I have modified it several times, all of which gave me segmentation faults, so this is the only version that runs.
What is happening, is that the code is cycling through, and deleting not only the element you want to get rid of, but all elements preceding it. So, if you want to delete the last element, everything in the list goes. Or, if you wanted to delete the second element, the first and second go, and so on.
It thinks that every name entered is the top name for some reason.
static void menu_delete_employee(void)
{
char deletename[MAX_NAME_LENGTH+1];
char namecheck[MAX_NAME_LENGTH+1];
int errorcheck = 0;
int foundit = 0;
fprintf(stderr, "Enter the name of the employee you wish to delete\n");
gets(deletename);
employee_list = top;
employee_list->name;
do
{
strcpy (namecheck, employee_list->name);
printf("namecheck = %s\n", namecheck);
errorcheck = (strcmp (namecheck, deletename));
printf("errorcheck = %i\n", errorcheck);
switch (errorcheck)
{
case 0:
{
printf("This is the right name\n");
foundit = 1;
if (employee_list->prev == NULL)
{
printf("top name\n");
top = employee_list->next;
}
else
{
if (employee_list->next == NULL)
{
printf("last one\n");
temp = employee_list->prev;
temp-> next = NULL;
free (employee_list);
}
else
{
printf("somewhere in the middle");
temp = employee_list->prev;
temp->next = employee_list->next;
employee_list->next->prev = temp;
free (employee_list);
}
}
printf("delete successful\n");
break;
}
default:
{
printf("not this one\n");
errorcheck = 0;
employee_list = employee_list->next;
break;
}
}
}
while (foundit == 0);
if (foundit == 0)
printf("Name not recognised\n.");
return;
}
Any help would be much appreciated.

Answer 1

Maybe the doubly-linked list is not built up the way you think it should. This has to be checked first.
Assuming the topology is correct, there are still a couple of issues with this code:
employee_list->name; (just above the do loop): what is this?
strcpy (namecheck, employee_list->name); : you do not need to copy, this is just a shorthand, so namecheck could be a (const) string pointer.
switch (errorcheck) : this has only 2 arms, why don't you use an if ?
if (employee_list->prev == NULL) ...: you just move the top pointer here but do not delete the top item, this will cause memory leaks. You also do not set the prev pointer of the next-to-top item to NULL.
In the "somewhere in the middle" part: you free employee_list which is the current position pointer. The next item to be processed should be temp->next, right? This is probably your problem because you do not take care of moving the current pointer along. Moreover, it is much better to set a pointer explicitly called tobedeleted to the item to be deleted, make sure the pointer used to iterate along the list (employee_list in your case) is moved appropriately, and when *tobedeleted is appropriately isolated out from the doubly linked list then issue the free(tobedeleted) command.
employee_list = employee_list->next; : you should check for employee_list turning into NULL at the last item, and exit the loop. Otherwise Bad Things will happen.
Final advice: you really need to consult a good C book... Kernighan and Ritchie
for instance. Way better than "Internet research".