Linked list problem

[hydeous]

Hi, I'm having a strange problem with my linked list program.
This is slightly embarrassing because I'm getting back to coding in C++ after 4 years and don't remember much.

This is the code

#include<iostream.h>
#include<conio.h>
#include<string.h>


void printList(struct node *&);

struct node
{
node* next;
int data;
};

int main()
{
clrscr();

node *node1, *node2, *node3, *node4;
node1->data = 1;
node2->data = 2;
node3->data = 3;
node4->data = 4;

node1->next = node2;
node2->next = node3;
node3->next = node4;
node4->next = node1;

printList(node1);

getch();
return 0;
}

void printList(node*& head)
{
node* current = head;
int counter = 0;
while(current != NULL && counter < 10)
{
cout<<"\n "<<current->data;
current = current->next;
counter++;
}
}

It doesn't seem to be accessing node4, could someone point me towards what's wrong? Thanks.

[rxlim]

You must allocate memory for your nodes.

[hydeous]

:D

okay, changed the code to

node *node1 = new node;

Thanks! Why did it print the first three nodes though? How did it allocate memory if I didn't allocate memory initially?

[rxlim]

Since your pointers are located on the stack they got the values that happen to be there, which might be a valid memory address, or not. A function's stack frame, which is the memory that the compiler allocates for your local variables, is not cleared (set to 0) when a function returns or when a new stack frame is allocated (normally). This means that the stack may contain more than just random data since parts of previous stack frames might be reused.

[hydeous]

I see.
Thanks for your help.