Question

I am just starting to learn C and (of course) struggling with pointers 🙂

Given this snippet:

int *storage, *storage_p;
storage = malloc(sizeof(int[GROW_BY]));
storage_p = storage;
// do something with storage, using storage_p
free(storage);
storage = NULL;

Is it really necessary to have two variables declared to work with the malloc()‘ed data? Is it good practice to create a storage and storage_p the way I did? If not, what would would be ‘the way’?

Answer 1

You will need a pointer that will hold the value returned by malloc(), so that you can free it later.

If what you plan on using storage_p for is going to change it value, then you are going to need two pointers.

However, I generally keep the pure initial pointer, and create new ones, ad hoc, as I need one.

int *storage = (int*) malloc(sizeof(int[GROW_BY])); 
// :
int* ptr = storage;
while (*ptr)
{
  // :
  ++ptr;
}