Thread: Linked List problem

I am writing a few functions for link lists, but I can't get these to work, and I can't see what the problem is. The NewList() function works, but the other two don't. If I use these functions to make two lists which are linked, then they end up pointing to each other, and so the linked lists makes a cycle.

Code:

struct DATA {
       int val;
       struct DATA *link;
       };
       
typedef struct DATA INFO;
typedef INFO *LISTPTR;

LISTPTR NewList(void);
LISTPTR AddListStart(LISTPTR base);
LISTPTR AddListEnd(LISTPTR base);

LISTPTR NewList(void)
{
        LISTPTR base=NULL;
        base = (LISTPTR)malloc(sizeof(INFO));
        
        if(base != NULL) {
                base->link = NULL;
                return base;
                }
                
        return NULL;
}

LISTPTR AddListEnd(LISTPTR base)
{
        LISTPTR temp=NULL;
        LISTPTR current=NULL;
        
        if(base != NULL) {
                current = base;
                while(current->link != NULL) {
                                    current = current->link;
                                    }
                                    
                temp = (LISTPTR)malloc(sizeof(INFO));
                
                if(temp != NULL) {
                        current->link = temp;
                        temp->link = NULL;
                        }
                }
        FreePointers(temp, current, NULL);
        return base;
}

LISTPTR AddListStart(LISTPTR base)
{
     LISTPTR temp;
     LISTPTR current;
     
     if(base == NULL) {
             // This function doesn't start a new list, NewList() does that
             }
             else {
                  temp = (LISTPTR)malloc(sizeof(INFO));
                  
                  if(temp != NULL) {
                          temp->link = base;
                          base = temp;
                          }
                  }
     
     FreePointers(temp, current, NULL);
     return base;
}

Link lists work because the pointers to data aren't freed until you're done with a part of or the whole list.