Iteration in C

Hi there /prog/.

I know Python, and I'm learning C. Both langs have for loops. Python's nicely iterates over a collection of unknown length. C's usually has you specify the length of the collection at compile time, but what if the length is unknown?

My best newbie guess: you terminate the collection with NULL, or you write an iteration function that returns some end-of-collection value when it's done.

>>24
like this?
#define MALLOC_ARRAY(t, s) ((t)malloc(sizeof(t) * (s + 1)) - 1)
#define FREE_ARRAY(p) free((p) - 1)
...
int *int_array = MALLOC_ARRAY(int, 10);
...
FREE_ARRAY(int_array);