Thread: Delete and destroy in double linked lists

so here you free LISTdt which is on the stack or do you allocate ListDt and allocate after that the linked list ? if not then thats your problem and it would lead to other problem on noticed one in deleteDList in which ur deleting all including head.

Originally Posted by kira_coder

so here you free LISTdt which is on the stack or do you allocate ListDt and allocate after that the linked list ? if not then thats your problem and it would lead to other problem on noticed one in deleteDList in which ur deleting all including head.

This is were I create my list

Code:

ListDT *createDList()
// returns a pointer to the header cell of the created list
{

 ListDT *List=(ListDT*) malloc( sizeof (ListDT) );
 if (List != NULL)
      {
       List->size=0;
       List->first = NULL;
       List->last = NULL;
      }

 return List;
}

My main.c has only this:

Code:

ListDT *L=NULL;
    L=createDList()
    destroyDList(L);
    printDList(L);

I'm just trying to find out how this works.
It runs at infinity, printing a large number over and over again (eg. 7864235) (an adress I think)

So once you destroy the list, you lose the memory. L still points to that piece of memory, but now it has ... something ... in it, that is not necessarily your list. (Hence the suggestions to set L to NULL in your main, once you get back from the destroy function.) Any attempts to use that pointer after you've freed it are doomed to heartache.

Originally Posted by tabstop

So once you destroy the list, you lose the memory. L still points to that piece of memory, but now it has ... something ... in it, that is not necessarily your list. (Hence the suggestions to set L to NULL in your main, once you get back from the destroy function.) Any attempts to use that pointer after you've freed it are doomed to heartache.

It works. Thanks.

I'm working on a exact same code.

Is it possible to get your function to point L to NULL somehow, as it is user friendly.