Thread: add node in a list

i'm having troubles with this, it compiles fine, but doesn't printf anything, it seems that no nodes are added to the list at all

Code:

#include <stdio.h>
#include <stdlib.h>

struct node 
{
  int dat;
  struct node *next;
};
typedef struct node* link;

void addnode(link *list, int d);
void delall(link *list);
int count(link list);

int main(void)
{
  link root = NULL, index; 
  int x;

  for (x = 0; x < 5; x++)
    addnode(&root, x);
  
  for (index = root; index != NULL; index = index->next)
    printf("%d ", index->dat);

  putchar('\n');

  printf("%d nodes\n", count(root) );

  delall(&root);

  return 0;
}


void addnode(link *list, int d)
{
  link new;
  link cur = *list;
  new = malloc( sizeof(*new) );
  if (new == NULL)
    exit(1);
  else
    new->dat = d;

  while (cur != NULL)
    cur = cur->next;

  cur = new;
  new->next = NULL;

}

void delall(link *list)
{
  link cur = *list, sav;
  while (cur != NULL)
  {
    sav = cur->next;
    free(cur);
    cur = sav;
  }
}

int count(link list)
{
  link cur = list;
  int c = 0;
  while (cur != NULL)
  {
    cur = cur->next;
    c++;
  }

  return c;
}

problem is on this loop

Code:

while (cur != NULL)
    cur = cur->next;

this runs as long cur is null and when you are at list end
previous node->next wont point any allocated mem. area.
so assigning new to cur don't have any effects to cur previous
node->next. it changes only cur to point new.

run loop as long cur->next is not null
and assigning
cur->next = new;
cur = cur->next.

Code:

void addnode(link *list, int d)
{
  link new;
  link cur = *list;
  new = malloc( sizeof(*new) );
  if (new == NULL)
    exit(1);
  else
    new->dat = d;

  while (cur->next != NULL)
    cur = cur->next;

  cur->next = new;
  cur = cur->next;

}

Segfault

I've tried this also, no segfault, but the output is still '0 nodes'.

Code:

void addnode(link *list, int d)
{
  link new;
  link cur = *list;
  new = malloc( sizeof(*new) );
  if (new == NULL)
    exit(1);
  else
    new->dat = d;

  if (cur == NULL)
  {
    cur = new;
    cur->next = NULL;
  }
  else
  {

    while (cur->next != NULL)
      cur = cur->next;

    cur->next = new;
    new->next = NULL;
  }

}

it works perfectly!! thanks Prelude
however, I don't understand where my mistake was and why was it printing 0 nodes?

That's naturally one way to go about it, but I get the impression that viaxd wants the function to accept an empty list (signified by a null pointer for the root node) and treat it accordingly.

Yes, exactly what i wanted, i believe that is called the head pointer, null tail linked list type (i'm so confused in all these list types right now )