Deallocation of 3 dimensional array in C++

Question

I am creating the array like this in the header file:

double (*arrayName)[b][c];

And allocating it like this in the cpp file:

arrayName= new double[a][b][c];

Where a, b, and c are constants based on the size of the data I am dealing with.

How do I deallocate this array? I tried doing the suggestion in Deallocation of 3 dimensional array, but that gives me a "Warning C4154: deletion of an array expression; conversion to pointer supplied" and causes a heap corruption error.

I'd prefer to not change to vectors as I am working with legacy code that is being repurposed but needs to stay as similar to the original as possible. I've already had to change from using static allocation to new/delete, as with the scale of the data we are working with it was overflowing the stack.

Edit: WhozCraig's method appears to be correct. I thought the way I was deallocating this array (and others like it) was my problem, but I noticed another issue in my code. I think I've fixed that, and I'll report back once my program is done rerunning (will take a day or two at least). Thanks for everyone who responded.

Edit 2: Things still aren't working 100%, but the issues are outside the scope of this question and I was able to tweak some values to get things working well enough to get the job done. Thanks again for all who responded.

Odds are extremely good that you're better off using `std::vector` rather than C-style arrays. And if you really insist on doing (de)allocation yourself, you're best off just using pointers, not arrays and pointers in combination. — KRyan, Oct 02 '12 at 17:49
http://stackoverflow.com/questions/8579207/hypercube-with-multidimensional-vectors see this answer for how to do it with `std::vector` — pyCthon, Oct 02 '12 at 17:52

WhozCraig · Accepted Answer · 2012-10-17T22:28:48.697

The vector-delete should work for this.

static const int b = 10;
static const int c = 10;
double (*arrayName)[b][c] = NULL;
arrayName = new double[10][b][c];
delete [] arrayName;

If you must allocate this dynamically and immediately like this, and want proof that destructors are fired correctly...

#include <iostream>
using namespace std;

class MyObj
{
public:
    MyObj() : val(1.0) {};
    ~MyObj() { cout << "~MyObj()" << endl;}

private:
    double val;
};

int main()
{
    static const int b = 3;
    static const int c = 3;
    MyObj (*arrayName)[b][c] = NULL;
    arrayName = new MyObj[3][b][c];
    delete [] arrayName;
    return 0;
}

will result in the following output (don't bother counting, there are 27 of them)

~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()
~MyObj()

That is what I am doing. I was not 100% sure if it was correct because my program was running out of memory, so I figured that I may have been deallocating the multidimensional arrays wrong. Thanks for the verification! — Dillon Welch, Oct 02 '12 at 20:14

Deallocation of 3 dimensional array in C++

1 Answers1