Function to delete dynamically allocated 2D array

Question

Quick question here. Using this func to allocate memory for an arr:

int **createDynamicNumArray() {
int size;
cout << "Enter size: " << endl;
cin >> size;
int **numArr = new int *[size];
for (int i = 0; i < size; ++i) {
    numArr[i] = new int[size];
}
return numArr;
}

Is this the correct way for a function to clear said memory?:

void delArr(int **&numArr, int size) {
for (int i = 0; i < size; ++i) {
    delete[] numArr[i];
}
delete[] numArr;
}

Key note: Do I pass just a double pointer or a double pointer reference to the function for deleting?

Thank you in advance

FWIW, if you use a std::vector<std::vector<int>> numArr(size, std::vector<int>(size)) you don't need to worry about cleaning anything up. — NathanOliver
– NathanOliver, Commented Mar 2, 2022 at 20:49
No need for reference in this case unless you want to change where the caller's pointer points. Just having the pointer is sufficient to delete the object at the pointer. — user4581301
– user4581301, Commented Mar 2, 2022 at 20:50
To directly answer the (first) question: Yes, that would work. But it would resemble C code, in a language that has gone to great lengths to eliminate the need for bug-prone memory micro-management like this. — Drew Dormann
– Drew Dormann, Commented Mar 2, 2022 at 20:53

eerorika · Accepted Answer · 2022-03-02 21:02:03Z

3

Is this the correct way for a function to clear said memory?:

Yes.

Key note: Do I pass just a double pointer or a double pointer reference to the function for deleting?

Both work. I recommend not using a reference since that will be less confusing to the reader.

However, I recommend avoiding owning bare pointers in the first place. In this case, std::vector<std::vector<int>> could be appropriate.

Or, more efficient (probably; depends on how you intend to use it) alternative would be to use a single dimensional vector and translate the indices.

edited Mar 2, 2022 at 21:02

answered Mar 2, 2022 at 20:54

eerorika

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1 Comment

user4581301 Over a year ago

Very simple example of a std::vector-based 1D matrix as mentioned in the last paragraph.

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