I have char* flexible array member stored within a stuct. Each of the values within the flexible array member have been strdup'd. I am unsure as how to free each of the strdup'ed values since I do not know exactly how many elements I have stored in the char* flexible array member.
This is my struct with the flexible array member;
struct Mall{
char *mallName;
char *shops[]; <--- Flexible array member which stores shop names in the mall
} Mall;
Since you allocate room for the flexible array member, you must know the number of shops at some point. This allows you to choose from multiple options. The ideas presented below are all functions that assume you pass the shops array itself and the extra item mentioned, where applicable:
object_count methodYou could track the number of shops added (add something like size_t shop_count; to the structure definition). Freeing the strings is as simple as:
void
free_shops(
char **shops,
size_t n)
{
while (n-- > 0)
free(my_mall->shops[n]);
}
You could also use a sentinel value (e.g. a null pointer) as an extra member, so you'd allocate shop_count + 1 shops every time. In that regard, it's no different than the other two options since you still allocate an extra bit of memory to store the sentinel value:
void
free_shops(char **shops)
{
for (; *shops != NULL; ++shops)
free(*shops);
}
end pointer methodAnother, perhaps more complex method, is a variation of tracking the number of shops added. Since you allocated the flexible array member, you know how many shops there are at some point. All you'd need to do is add a char **end_shops; member and assign my_mall->shops + shop_count to it whenever you know the shop count. Then when you want to free the strings allocated by strdup():
void
free_shops(
char **shops,
char **end)
{
while (end-- != shops)
free(*end);
}
If you didn't have an object count, you'd be stuck with the sentinel method only as the others rely on arithmetic. Of course, if you iterated through the array to find the sentinel value, that would allow you to determine the object count, though you could just as easily free things while searching for the sentinel value, making it pointless to do so in the first place. :P
