Question

I have a structure as follows:

struct something{
  char *string_member;

};

now I created

struct something *s = malloc(sizeof(struct something));

s.string_member = malloc(5); //one way
s.string_member = "some thing wrong"; // second way

While I free the memory pointed by s. How do I free the memory allocated to string_member in the both the cases. Do I have to worry about string_member in second case at all?

Answer 1

You mustn’t free it in your second way example, and you have no way to (portably) make the difference between case one and case two by just looking at the pointer. So don’t do that, make sure you always allocate the string_member using malloc or e.g. strdup. That way, you can always free it (once).

s.string_member = strdup("some thing wrong");  // the other way

...

free(s.string_member);