bad access error when pushing back vector - c++

Question

I have these two classes:
class card { //class that represents a card
int cardNumber; //the ID of the card that give it itse level and suit
std::vector<std::string> suits = { "hearts", "spades", "diamonds", "clubs" };
std::vector<std::string> levels { "Ace", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "Jack", "Queen", "King"};
std::string suit;
std::string level;
public:
card(int nCardNumber) { //constructor that initiliazes all properties of the card
cardNumber = nCardNumber;
level = levels[cardNumber%13];
suit = suits[cardNumber/13];
}
void printValue() { //prints the cards level and suit
using namespace std;
cout << level << " of " << suit << endl;
}
};
and
class hand { //represents the hand a player is holding
int playerNumber;
std::vector<card> playerHand; //vector of carsa
public:
hand(int m_playerNumber) {
playerNumber = m_playerNumber;
}
void addCard(int cardNumber) { //adds a card to the hand
card cardToBeAdded(cardNumber);
cardToBeAdded.printValue();
playerHand.push_back(cardToBeAdded);
}
void printHand() {
using namespace std;
cout << "Player " << playerNumber << " has:" << endl;
for (int i = 0; i < 2; i++) {
playerHand[i].printValue();
}
}
};
and whenever I call the addCard function in hand, I get EXC_BAD_ACCESS (code=1).
I've tried some debugging by declaring two members in the playerHandVector and changing the function to rewrite those values as opposed to appending new ones to the vector, but same error.
Any help would be appreciated!

Answer 1

With some proper debugging, it's pretty easy to see what's going on. I've reduced your example to the very minimum that will reproduce your bug, because I don't believe it's to do with std::vector::push_back.
#include <iostream>
#include <vector>
#include <string>
class card { //class that represents a card
int cardNumber; //the ID of the card that give it itse level and suit
std::vector<std::string> suits = { "hearts", "spades", "diamonds", "clubs" };
std::vector<std::string> levels { "Ace", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "Jack", "Queen", "King"};
std::string suit;
std::string level;
public:
card(int nCardNumber) { //constructor that initiliazes all properties of the card
cardNumber = nCardNumber;
std::cout << cardNumber % 13 << std::endl;
std::cout << cardNumber / 13 << std::endl;
level = levels[cardNumber%13];
suit = suits[cardNumber/13];
}
void printValue() { //prints the cards level and suit
using namespace std;
cout << level << " of " << suit << endl;
}
};
int main() {
std::vector<card> v;
for (size_t n = 0; n <= 52; ++n)
{
// Replicate "addCard" function
card c(n);
c.printValue();
v.push_back(c);
}
return 0;
}
You'll notice two things here: I've added some debugging help to the card constructor because I believed the problem was the access of the std::vector<std::string> and I'm attempting to add all 52 cards. 'lo and behold, the first 51 cards add successfully; however, trying to add the king of clubs has an error. Let's see why:
card(int nCardNumber) { // nCardNumber = 52;
cardNumber = nCardNumber; // 52
const int nCard = cardNumber % 13; // King
const int nSuit = cardNumber / 13; // 4
level = levels[nCard];
suit = suits[nSuit]; // whoops, out of bounds!
}
You can see here that you are trying to access the suits[4] which is out of bounds.

Answer 2

You probably have some code (which you haven't shown) which is using cardNumber as an array index, not cardNumber % 13 or similar and going out of array bounds.
Using cardnumber/13 as an array index will also fail if cardNumber is 52 or more.
Also .....
suits and levels are non-static members of card, so every instance of card will have its own copy of those vectors.
I wouldn't expect a problem to occur with every call of hand::addCard() but, if your code is creating lots of hands, adding lots of cards to them, and not cleaning up - then it will exhaust available memory quicker than you probably intend.
If you are then running into limits on available memory (that depends on you OS, available RAM, etc) then that would explain your problem.

Answer 3

This compiles and runs "correctly" on Visual Studio 2013 Community. Well, except that VS2013 doesn't do member initalizer lists so I had to, ugh, type those out. The only way I could get an error was to have a value outside of the obvious range of cards (>52, <0). Is that what you're doing?
Other issues: normal card decks don't have a '1' card, delete the 1 from the levels vector. After doing that, run this in main:
for (int i = 0; i < 52; ++i)
playerHand.addCard(i);
On mine it spits out all the cards, A to K, for all 4 suits, in order. However if I give it a value outside of those bounds it will give an error.
It's safer to get a value from the vector using vector.at(index) than the [] operator. The [] operator on a vector treats it just like a raw C-array, so if you don't have some kind of debugger running to catch it, it'll be undefined behavior if you feed it an inappropriate value. That means if you're lucky it crashes with no explanation. One of the advantages of a vector is that you can use the at method to summon the index, and throw an exception with a pretty clear name.
Also, if you have a function that calls for user input and it's possible to feed wrong numbers (as it is in this case), then it's a good idea to check the input to make sure it's good.
As Peter points out, using vectors in the class just to hold labels is inelegant, and wastes memory. An easy solution would be to make the variables:
static std::vector<std::string suits...
The static keyword means, among other things that you should definitely look into, that they will only be created once and persist across all instances of the class.