I have a linked list structure

struct node {
 int data;
 node next;
}

and a function

struct node *insert_sorted (struct node *nodes, 
  int d) {
  // todo
}

I need to implement this so that, given a new piece of data, it constructs a new node and inserts into the linked list in sorted order.

The first thing I want to check inside of the insert_sorted function is whether nodes points to nothing or something. By that I don’t mean checking whether the pointer is NULL, which I’m familiar with. I mean that I want to check whether the address nodes holds a node struct or not. I think if this were Java I might be able to write

if (nodes == null) {
  ...
}

but I don’t think there is an analogous thing to do in C.

I know that I could try to manage the nodes pointer so that, if it is non-null then it always points to some struct. I’ll probably end up doing this.

But I just want to know if there exists a more direct way of solving the issue. Is there any way to take a given non-null pointer and check whether it points to anything or not?