Newbie Pointer question

Hi-
What's the diffreence between doing this:

Code:

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

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and this:

Code:

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

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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.

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!

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.

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

Thanks!

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

Quote:

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Originally Posted by CornedBee

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

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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++.