How do I get rid of a NULL segmentation fault?

I am creating a linked list program in C and I keep on getting a segmentation fault. I've narrowed the problem down to a few lines of code and I believe i开发者_如何学Pythont has to do with checking for NULL. How can I fix this? Here's the code:

typedef struct node
{
  int contents;
  struct node *nextNode;
}  Node;



deleteNode(Node *currentNode)
{

  while((currentNode->contents) != NULL)
  {
    //.....Do Stuff.....
    currentNode = currentNode->nextNode;
  }
}

Thanks

Try checking to make sure that currentNode isn't NULL at the start of deleteNode(). I.e.

deleteNode(Node *currentNode)
{
    if (currentNode == NULL) return;
    // ...
    // ...
}

If the problem is as I suspect, currentNode is a null pointer. Just ensure that currentNode is not null before you attempt to access it.

deleteNode(Node* currentNode)
{
    while ((currentNode != NULL) && (currentNode->contents != NULL))
    {
        /* ... */
        currentNode = currentNode->nextNode;
    }
}

Well, I'm suspicious that this line:

while((currentNode->contents) != NULL)

is comparing the contents field of your Node structure, which is an int, with NULL... I would guess that this was supposed to be checking currentNode->nextNodeinstead!

So, probably: none of your contents are zero, so this test is true for every item in the list. Then the last item has a NULL currentNode->nextNode, which is assigned to currentNode, and it blows up dereferencing it the next time round the loop.

what happens when currentNode is NULL?. It is dereferencing a NULL memory in the while condition.