C++ Program crashes when executing object functions

Question

Here is part of the code:

class Inventory {
    public:
        void PrintInventory();
        void AddItemToInventory();
        void UpdateItemQtyInInventory();
        void RemoveItemFromInventory();
    private:
        vector<Item*> inventory;
};

void Inventory::PrintInventory() {
    unsigned int i = 0;
    if (inventory.size() == 0) {
        cout << "No items to print." << endl;
    } else {
        for (i=0; i < inventory.size(); ++i) {
            cout << i << " - ";
            inventory.at(i)->Print();
        }
    }
    return;
}

void Inventory::AddItemToInventory() {
    string usrInptName = "";
    string usrInptQntyStr = "";
    string usrInptPriceStr = "";
    string usrInptOptn = "default";
    istringstream inSS;
    int usrInptQnty = 0;
    int usrInptPrice = 0;
    string usrInptOther = "";
    bool valid = false;

    while (valid == false) {
        cout << "Enter (b)ook or (p)roduce: ";
        getline(cin, usrInptOptn);

        if (usrInptOptn.size() == 0) {
                continue;
        } else if (usrInptOptn.at(0) == 'p') {
            Produce* prdct;

            cout << "Enter name of new produce: ";
            getline(cin, usrInptName);

            cout << "Enter the price per item: $";
            getline(cin, usrInptPriceStr);
            inSS.str(usrInptPriceStr);
            inSS >> usrInptPrice;
            inSS.clear();

            cout << "Enter quantity: ";
            getline(cin, usrInptQntyStr);
            inSS.str(usrInptQntyStr);
            inSS >> usrInptQnty;
            inSS.clear();

            cout << "Enter expiration date: ";
            getline(cin, usrInptOther);

            prdct = new Produce;
            prdct->SetName(usrInptName);
            prdct->SetPrice(usrInptPrice);
            prdct->SetQuantity(usrInptQnty);
            prdct->SetExpiration(usrInptOther);

            inventory.push_back(prdct);
            valid = true;

        } else if (usrInptOptn.at(0) == 'b') {
            Book* prdct;

            cout << "Enter name of new book: ";
            getline(cin, usrInptName);

            cout << "Enter the price per item: $";
            getline(cin, usrInptPriceStr);
            inSS.str(usrInptPriceStr);
            inSS >> usrInptPrice;
            inSS.clear();

            cout << "Enter quantity: ";
            getline(cin, usrInptQntyStr);
            inSS.str(usrInptQntyStr);
            inSS >> usrInptQnty;
            inSS.clear();

            cout << "Enter Author: ";
            getline(cin, usrInptOther);

            prdct = new Book;
            prdct->SetName(usrInptName);
            prdct->SetPrice(usrInptPrice);
            prdct->SetQuantity(usrInptQnty);
            prdct->SetAuthor(usrInptOther);

            inventory.push_back(prdct);
            valid = true;
        } else {
            cout << "Invalid choice\n";
        }

    }

    return;
}

Inventory* inventory;

int main() {
    string usrInptOptn = "default";

    while (true) {
        // Get user choice
        cout << "\nEnter (p)rint, (a)dd, (u)pdate, (r)emove, or (q)uit: ";
        getline(cin, usrInptOptn);

        // Process user choice
        if (usrInptOptn.size() == 0) {
            continue;
        } else if (usrInptOptn.at(0) == 'p') {
            inventory->PrintInventory();
        } else if (usrInptOptn.at(0) == 'a') {
            inventory->AddItemToInventory();
        } else if (usrInptOptn.at(0) == 'u') {
            inventory->UpdateItemQtyInInventory();
        } else if (usrInptOptn.at(0) == 'r') {
            inventory->RemoveItemFromInventory();
        } else if (usrInptOptn.at(0) == 'q') {
            cout << "\nGood bye." << endl;
            break;
        }

    }

    return 0;
}

The program crashes when it is running the functions. I don't have the slightest idea why. The AddItemtoIventory function runs through it's entirety before the program crashes while the other one ,and the others, just crashes.

What about using the debugger to step through your code, and ask a more specific question? — πάντα ῥεῖ, Nov 21 '14 at 18:28
`Inventory* inventory;` <- this. This is uninitialized and bad. 1. You don't need a global here. 2. You don't need a pointer here. — crashmstr, Nov 21 '14 at 18:28
It would be helpful if you could post crash logs related to this issue — Paul Renton, Nov 21 '14 at 18:28
You call through a `NULL`-pointer and wonder why all hell breaks loose? Isn't it obvious? — Deduplicator, Nov 21 '14 at 18:31
Include your Inventory pointer inside main and initialise it by using new and calling the constructor for Inventory class. You are invoking functions on a pointer that points to nothing. — itachi, Nov 21 '14 at 18:33
So "my understanding of C++ is feeble at best, BTW I am qualified to know that is not a dupe" interesting — Lightness Races in Orbit, Nov 21 '14 at 18:35
I don't understand pointers. I have no idea what a null instance is or what it has to do with this. I thought Inventory* inventory; was initializing the object. To sum everything up I don't know what the hell I'm doing, ok. So no this isn't a dupe because that other question doesn't help me at all. — Eegxeta, Nov 21 '14 at 18:50

Paul Renton · Accepted Answer · 2014-11-21T19:40:19.907

-1

You do not need a global variable here. Just create an inventory object within the scope of main

int main() {
    Inventory inv;
    // Rest of your code below

    return 0;
}

Or, alternatively you can still use a pointer and use new.

int main() {
    Inventory* inv = new Inventory;
    // Rest of your code below

    return 0;
}

edited Nov 21 '14 at 19:40

answered Nov 21 '14 at 18:32

Paul Renton

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That's simply wrong. (First two sentences) Static and thread-local memory is always statically initialized at a minimum. – Deduplicator Nov 21 '14 at 18:33
@Deduplicator: s/sweet/plain/ – Lightness Races in Orbit Nov 21 '14 at 18:44

C++ Program crashes when executing object functions

1 Answers1