C free an array multidimensional correctly

Question

I have this following code, and i really don't understand why i have this segmentation fault

static char** game_alloc(char **game, int n, int m) {
    game = calloc(n, sizeof(char *));
    for(int i = 0; i < n; i++)
    {
        game[i]= calloc(m, sizeof(char));
    }
    if(*game == NULL) {
        perror("Error: calloc in not initialized correctly");
        exit(EXIT_FAILURE);
    }
    return game;
}

static void game_free(char **game, int n) {

    for (int i = 0; i < n; i++) { 
        free(game[0]);
    }
    free(game);
}

The problem is when i call the function game_free. I have a segementation fault with the free

When i run it into valgrind i have this :

==11449== Use of uninitialised value of size 8
==11449==    at 0x400AE5: game_free (john.c:27)
==11449==    by 0x400DAE: main (john.c:114)
==11449== 
==11449== Invalid free() / delete / delete[] / realloc()
==11449==    at 0x4C29730: free (vg_replace_malloc.c:468)
==11449==    by 0x400AEF: game_free (john.c:27)
==11449==    by 0x400DAE: main (john.c:114)
==11449==  Address 0x495641ff89415741 is not stack'd, malloc'd or (recently) free'd
==11449== 
==11449== Conditional jump or move depends on uninitialised value(s)
==11449==    at 0x4C296E6: free (vg_replace_malloc.c:468)
==11449==    by 0x400B07: game_free (john.c:29)
==11449==    by 0x400DAE: main (john.c:114)
==11449== 
==11449== Invalid free() / delete / delete[] / realloc()
==11449==    at 0x4C29730: free (vg_replace_malloc.c:468)
==11449==    by 0x400B07: game_free (john.c:29)
==11449==    by 0x400DAE: main (john.c:114)
==11449==  Address 0x400f10 is in the Text segment of /autofs/netapp/account/cremi/mpuygren/MasterCSI/projet/john-2/john
==11449== 
==11449== 
==11449== HEAP SUMMARY:
==11449==     in use at exit: 33 bytes in 4 blocks
==11449==   total heap usage: 4 allocs, 4 frees, 33 bytes allocated

Don't understand, i follow this post but ....

C: Correctly freeing memory of a multi-dimensional array

Just to spread the word, this is **not** a multidimensional array. It is only an emulation of it. C has real multidimensional arrays with variable bounds since 1999. Among other things you would avoid this particular problem by using the correct tool from the start. — Jens Gustedt, Sep 11 '14 at 20:36

ani627 · Answer 1 · 2014-09-11T19:06:08.237

3

It should be free(game[i]);, instead of free(game[0]);

edited Sep 11 '14 at 19:06

answered Sep 11 '14 at 18:57

ani627

5,578
8
39
45

score 1 · Accepted Answer · answered Sep 11 '14 at 18:56

1

Instead of:

for (int i = 0; i < n; i++) { 
        free(board[0]);
    }

write:

for (int i = 0; i < n; i++) { 
        free(board[i]);
    }

answered Sep 11 '14 at 18:56

Igor Pejic

3,658
1
14
32

C free an array multidimensional correctly

2 Answers2