Trouble creating a new array when old one is full

Question

I'm currently trying to implement my own version of a stack, which will be an array that contains structs. Here is the code:

struct some_struct{
    std::string name;
};

ExStack::ExStack(){
    cout << "Please enter a capacity for the stack: ";
    cin >> capacity;
    stack = new some_struct[capacity];
    size = 0;
}
    void ExStack::create_new_array(some_struct item){
        size ++;
        if (size == capacity){
        some_struct* new_stack = new some_struct[2 * capacity];
        for (int i = 0; i < size; i++){
            cout << stack[i];
            new_stack[i] = stack[i];

        }
        delete[] stack;
        stack = new_stack;
        capacity *= 2;
        delete[] new_stack;
    }

For debugging purposes, I'm currently entering 10 for the capacity of the ExStack, and then calling create_new_array until size == capacity. However, my code is crashing right when it gets to the for loop, as it tries to copy everything over to the new stack and delete the old stack. Any ideas?

what is the value of `capacity` when you enter that `if` statement? — sfletche, May 09 '15 at 01:56
Your code does not conform to any visible structure, making it hard to follow (global variables? ewww)... or just meaningless (for example `ExStack()` is never called). Anyway, your crash might be cause by your incorrect iteration of elements in `stack` in your `for` loop as you are exceeding the bounds of the array. — Dai, May 09 '15 at 01:56
@sfletche If the user enters 10 when the `ExStack` is created, capacity would be 10. It can hold 10 items at most. — Tyler, May 09 '15 at 01:57
@Tyler - did you put a `cout` statement in there to test your assumption? — sfletche, May 09 '15 at 01:59
How about `cout << stack[i];`...is that outputting anything? — sfletche, May 09 '15 at 02:02
This is terrible code, I find it hard to call this C++. I would *highly* recommend that you get a [decent book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) and actually learn the language. — Baum mit Augen, May 09 '15 at 02:04
@sfletche That is actually giving me an error. Operand types are std::ostream << some_struct — Tyler, May 09 '15 at 02:05
@Tyler - The code is very hard to follow as to what you're doing. You have a class called `ExStack` but you also have a stand-alone function called `create_new_array`. Shouldn't that function be a member of your ExStack class? — PaulMcKenzie, May 09 '15 at 02:14

score 2 · Accepted Answer · answered May 09 '15 at 01:56

2

You are deleting the new stack that you created at the end of your function.

delete[] new_stack;

You only need delete[] stack; to get rid of the old memory. The new memory that you allocated in new_stack needs to be kept.

answered May 09 '15 at 01:56

NathanOliver

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But the program is crashing even during the for loop. – Tyler May 09 '15 at 02:07
1

Then you really need to post an [MCVE](http://stackoverflow.com/help/mcve) or [SSCCE](http://sscce.org/). As is your `create_new_array()` function is missing a closing curly brace. – NathanOliver May 09 '15 at 02:29
Sorry, I tried out your solution and it worked! Thank you very much! – Tyler May 09 '15 at 06:42

Trouble creating a new array when old one is full

1 Answers1