Segmentation Fault when using memcpy with void pointers - C

Question

So I've been creating a doubly linked generic list in C. I have successfully created it with ints as the data stored but now I need to make it generic.

I have created a list and node variable type:

struct node{

  struct node *prev;
  struct node *next;
  void *item;

};

struct list{

  struct node *first;
  struct node *current;
  struct node *last;
  int itemSize;

};

I am having issues with inserting values into item in the node. I have the following code to insert a newNode before the current pointer.

void insertBefore(list *l, void *p){

  struct node *new = (struct node*) malloc(sizeof(struct node));
  new->item = malloc(l->itemSize);

  memcpy(new->item,p,l->itemSize);

...

Void pointer p is some data and itemSize is the number of bytes of said data. Of course this is not the whole insertBefore code, but the logic in that should be sound as I have made the list work with int as the type of item.

When I call this I get a Segmentation fault: 11 error and I am not sure why.

Any help would be very much appreciated!

edit:

I've included some of the other code called as that might be where stuff is going back, although the seg fault is at the memcpy in insertBefore

list *newList(int b){

  list *l = (list*)malloc(sizeof(list));
  l->itemSize = b;
  l->first = NULL;
  l->current = NULL;
  l->last = NULL;

  return l;
}

and then this is called in the main:

list *l = newList(sizeof(int));
insertBefore(l, (void *)3);
...

Answer 1

Your code attempts to memcpy(new->item, 3, sizeof(int)) You are getting segmentation fault because 3 is not a dereference able address.

Instead, you should do this:

int x = 3;
insertBefore(l, &x);