Lists are the most basic data structures

Everybody is implementing lists all the time

This is a trivial example, that reverses stdin lines to stdout

struct str_item { char str[16]; struct str_item *next; };
#define list_insert(h, new) \
     ({(new)->next = (h); (h) = (new);})
#define list_extract(h) \
     ({struct int_item *res = (h); if (h) (h)=(h)->next; res;})

        while (fgets(line, 16, stdin)) {
                item = malloc(sizeof(*item));
                memcpy(item->str, line, sizeof(item->str));
                list_insert(head, item);
        }
        while ( (item = list_extract(head)) ) {
                printf("%s", item->str); free(item);
       }