Free-before-overwriting code, how to fix memory leaks?

Asked Dec 02 '16 at 13:55

Active Nov 20 '17 at 04:05

Viewed 49 times

I have a function that uses two copies of a 2D array and does some mathematical operations on them, but I can free before overwriting. The code is something like this:

int **function(int **A)
{
    int **B = (int **)malloc(N*sizeof(int *));
    for(i = 0; i < N; i++)
         B[i] = (int *)malloc(M*sizeof(int));
    //the operations i need to do

   return B;
}

And in main the call is like this(A in int **):

A = function(A);

Is there a way to get rid of leaks without changing the code too much ?

edited Nov 20 '17 at 04:05

smci

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asked Dec 02 '16 at 13:55

Mihai Podaru

Inside `function()` deep-free `A` before returning. – alk Dec 02 '16 at 14:02
What do you mean ? for(i = 0; i < N; i++) free(A[i]); free(A); ? – Mihai Podaru Dec 02 '16 at 14:07
Yes, exactly this. – alk Dec 02 '16 at 14:09
I still get memory leaks if i do this. – Mihai Podaru Dec 02 '16 at 14:10
"*still get memory leaks*": Those then due to something else, you do not show us. How do you detect the leak(s)? – alk Dec 02 '16 at 14:12
BTW and unrelated, those casts to `malloc()` & Friends are useless in C. – alk Dec 02 '16 at 14:13
Does the code inside `function` (that you do not show us) by any means does `A[...] = ...` or `A = ...`? – alk Dec 02 '16 at 14:14
i use valrind --leak-check=yes – Mihai Podaru Dec 02 '16 at 14:16
1

Dare showing the Valgrind logs and the liens of code those logs refer to? – alk Dec 02 '16 at 14:16
Use Valgrind's option `--track-origins=yes` as well. – alk Dec 02 '16 at 14:17
It is a general question, but yes, i may have something like A[i][j] += B[j][i] or something. Is this the problem ? – Mihai Podaru Dec 02 '16 at 14:17
`A[x][y] = ....` is ok, as it modifies the array's elements. `A = ...` and `A[x] = ...` aren't, but change the pointers you allocated to create this "jagged" array. – alk Dec 02 '16 at 14:19

Free-before-overwriting code, how to fix memory leaks?

0 Answers0