Newbie Pointer question

[kook44]

Hi-
What's the diffreence between doing this:

Node *temp;
temp = new Node;
temp->data=x;

and this:

Node *temp;
Node n;
n.data = x;
temp = &n;

When I use the first one, I get the expected results for temp, so I guess that's correct, but I don't understand why the second one wouldn't also work.

[Slacker]

How wouldn't the second one work? Assuming you're doing everythng else right, the code you've posted is sound. Most likely you're trying to use local variables to build something like a linked list, and that usually ends up being an aliasing problem because all of the nodes point to the same memory.

Cheers!

[CornedBee]

The second snippet works, standing alone. But n will disappear once you leave the function you're in (presumably LinkedList::addNode or something similar), at which point temp will point to invalid memory. Allocating the node on the heap (with new) will prevent that.

[kook44]

yep, that was it - once the variable n gets descoped, I get all kinds of weird results. makes sense

Thanks!

[CornedBee]

You have no idea how much an advantage you have over most newbies for understanding that.

[kook44]

You have no idea how much an advantage you have over most newbies for understanding that.

Thanks.

Actually, I have 5 years programming experience in the java/web world. I'm just trying to get into desktop programming. Have to think back to my cs undergrad courses. It's hard getting back into the lower-level stuff and the syntax of C++.