Outputting a string pointer array

Question

I'm having a bit of trouble figuring out exactly what I am doing wrong here, and haven't found any posts with the same issue. I am using a dynamic array of strings to hold a binary tree with the root at [0], first row of children, left to right, at [1] and [2], etc. While I haven't debugged that output format yet, I am much more concerned as to why that specific line is crashing my program.

I thought it was a pointer de-referencing issue, but outStream << &contestList[i] prints addresses as I'd expect, and outStream << *contestList[i] throws errors as I'd expect them to.

//3 lines are from other functions/files
typedef string elementType;
typedef elementType* elementTypePtr;
elementTypePtr contestList = new elementType[arraySize];

void BinTreeTourneyArray::printDownward(ostream &outStream)
{
    int row = 1;

    for (int i = 0; i < getArraySize(); i++)
    {

        outStream << contestList[i]; //this is crashing the program

        if (isPowerOfTwo(i))
        {
            outStream << endl;
            row++;
        }
        else
        {
            outStream << ":";
        }
    }
}

arraySize is a private member arraySize = ((2 * contestants) - 1) where contestants is the number of contestants in my tournament. Each round or "row" in the tree is synonymous with a tournament bracket. If there are n contestants, then there are 2n-1 nodes needed in the tree. The issue wouldn't be with this function.

getArraySize() { return arraySize; }

"A string pointer array" Shudder! Any concise reasons to use arrays or pointers with your code? Could you elaborate about these please? — user0042
– user0042, Commented Dec 3, 2017 at 21:15
What is the value of arraySize when you call new? arraySize modified in any other place? — Michaël Roy
– Michaël Roy, Commented Dec 3, 2017 at 22:06
You probably shouldn’t use a raw pointer for your contestList. Instead, consider a std::vector<elementType>, or if the space overhead is a concern, std::unique_ptr<elementType[]>. — Daniel H
– Daniel H, Commented Dec 21, 2017 at 18:27

ViscousRandom · Accepted Answer · 2017-12-03 22:25:54Z

1

Turns out elementTypePtr contestList = new elementType[arraySize]; was the issue. contestList was a private member of the class, then I threw this line in a function declaring a local variable of the same name that disappears after the function ends. No biggie, except for the fact that I needed it in the print function...Oops.

answered Dec 3, 2017 at 22:25

ViscousRandom

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1 Comment

Daniel H Over a year ago

And this illustrates two of the reasons why I suggested unique_ptr in the question comments above. 1. This means you were leaking wenever you called the function which created contestList; a unique_ptr would have avoided that. 2. More importantly, with unique_ptr, this would have left the class member at nullptr, which would have made this a lot easier to debug.

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