Soustraction infinie

char *classic_sus_op(char const *str1, char const *str2)
{
    int i = my_strlen(str1) - 1;
    int j = my_strlen(str2) - 1;
    int k = 0;
    int rest = 0;
    char *result = malloc(sizeof(char) * (i + j + 1));
    int dec_i = 0;
    int dec_j = 0;
    int test = 0;

    while (i >= 0 || j >= 0 || rest != 0){
        dec_i = (i >= 0) ? str1[i] - '0' : 0;
        dec_j = (j >= 0) ? str2[j] - '0' : 0;
        test = dec_i - dec_j + rest;
        if (test < 0){
            result[k] = (test + 10) + '0';
            rest = 1;
        }
        if (test >= 0){
            result[k] = test + '0';
            rest = 0;
        }
        k++;
        i--;
        j--;
    }
    result[k] = '\0';
    result = my_revstr(result);
     if (result[0] == '0')
        my_putchar('0');
     else
         my_putstr(result);
     my_putchar('\n');
    return (result);
    free(result);
}

void infin_sus(char *av1, char *av2)
{
    int i = my_getnbr(av1);
    int j = my_getnbr(av2);

    if (i > j){
        classic_sus_op(av1, av2);
    } else {
        my_putchar('-');
        classic_sus_op(av2, av1);
    }
}

int main(int ac, char **av)
{
    infin_sus(av[1], av[2]);
}