Trying to learn pointers and structs, getting stuck (C)

Question

Hello. I've been reading along in the K&R (2nd ed, ofc!) and my aim is to make a simple blackjack clone as my first game. It's supposed to run in the terminal and have simple keystrokes for actions. I'm stuck on building the initial deck and a debug function to test and ensure the deck is built properly. What I have so far is in the following paste:
http://sprunge.us/JUMS?c
Understand that I'm sort of flailing about in my understanding of pointers and how they interact with structs. As far as I can tell, there are two ways to do this; with pointers and with array subscription. I'd prefer the latter if possible since it would be easier to understand, but I'd like to learn both. The problem I'm getting is that my deck isn't being built properly, which makes the test_deck() function return a few bogus cards and then a bunch of zeros (if it doesn't segfault!)
Any help would be great.

Answer 1

struct card nd;
struct card *pnd;
int suits;
pnd = &nd;
pnd++;
nd = *pnd;
Not good. "nd" is *one* instance of the struct, and "pnd" points to that. Incrementing "pnd" points it to a memory location after the end of the 'array' (which is only one element long). This is why it's segfaulting.
Here are two ways to do it, one using pointers and one using array indices (pointers in disguise). Both return a pointer to the deck (as it's an array), so the rest of your code will need to be slightly modified:
struct card* create_deck (void)
struct card* nd = (struct card*) malloc (sizeof (struct card) * 52);
struct card *pnd;
int suits;
pnd = nd;
for (suits = 1; suits <= 4; suits++) {
int n;
for (n = 1; n <= 13; n++) {
switch(suits) {
case 1:
pnd->suit = 'h';
break;
case 2:
pnd->suit = 'd';
break;
case 3:
pnd->suit = 'c';
break;
case 4:
pnd->suit = 's';
break;
pnd->value = n;
pnd++;
return nd;
struct card* create_deck (void)
struct card *nd = (struct card*) malloc (sizeof (struct card) * 52);
int suits, n, i;
i = 0;
for (suits = 1; suits <= 4; suits++) {
for (n = 1; n <= 13; n++) {
switch(suits) {
case 1:
nd[i].suit = 'h';
break;
case 2:
nd[i].suit = 'd';
break;
case 3:
nd[i].suit = 'c';
break;
case 4:
nd[i].suit = 's';
break;
nd[i].value = n;
i++;
return nd;
edit: Of course, you will also need to free the returned value at some point.
Last edited by Barrucadu (2011-01-25 18:11:17)