Freeing the memory - two dimensional array

Question

I use Visual C++ 2010 and I'm trying to use free() with two dimensional array:

#include <stdio.h>
#include <stdlib.h>
#define SIZE 8


int main(){

    int **matrix = (int**)malloc(sizeof(int*)*SIZE);
    int i;
    for(i=0; i<SIZE; i++){
        matrix[i] = (int*)malloc(sizeof(int)*SIZE);
    }
    for(i=0; i<SIZE; i++){
        free(matrix[i]);
    }
    free(matrix);
    getch();
    return 0;
}

Am I doing this right?

Regards.

So far, it looks right, are you geting crash or nasty effects ?.. — xtof pernod, Apr 17 '13 at 20:47
looks ok, I'd probably just allocate it in one malloc if you just want a matrix of ints. — Keith Nicholas, Apr 17 '13 at 20:49
@bash.d There are good arguments for and against casting malloc. Read about them and you will realize stating *Don't cast the return value of malloc* is futile. — , Apr 17 '13 at 20:50

Heisenbug · Accepted Answer · 2013-04-17T21:04:39.410

7

Basically it should be right.

Btw you don't need to call malloc for each row of the 2d array you are trying to allocate (unless you have specific reasons to do that).

You can use just one malloc and one free:

malloc(sizeof(int*)*ROW_NUM * COL_NUM);

Using a single call to malloc has also the benefits to allocate continuosly in memory the elements of your matrix.

edited Apr 17 '13 at 21:04

answered Apr 17 '13 at 20:50

Heisenbug

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why the downvote? The answer is right. At least give some reasons – Heisenbug Apr 17 '13 at 20:52
5

sometimes you just get them for no reason. – Keith Nicholas Apr 17 '13 at 20:56

score 2 · Answer 2 · edited May 23 '17 at 11:43

2

Looks like it. Although you can and probably should (for efficiency purposes) do just one malloc and one free as shown here

If you don't need to be in C explicitly, it might be worth taking a look at vectors to handle the memory for you.

edited May 23 '17 at 11:43

Community

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answered Apr 17 '13 at 20:51

bdwain

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Freeing the memory - two dimensional array

2 Answers2