Using macros in C to define data structures

Question

I am trying to wrap my head around the concept of using macros to define data structure operations. The following code is a simple example to use the built in list library i

Answer 1

First read this to get a hold what these macros do. And then go to queue.h. You'll get your treasure trove there!

I found a few gold coins for you-

#define STAILQ_HEAD(name, type)                                         \
struct name {                                                           \
        struct type *stqh_first;/* first element */                     \
        struct type **stqh_last;/* addr of last next element */         \
}

Lets dig in a bit deep and answer your questions

What is stailhead? This seems to be "just" defined.

#define STAILQ_HEAD(name, type)                                         \
struct name {                                                           \
        struct type *stqh_first;/* first element */                     \
        struct type **stqh_last;/* addr of last next element */         \
}
 STAILQ_HEAD(stailhead, entry) head =
 STAILQ_HEAD_INITIALIZER(head);
 struct stailhead *headp;            /* Singly-linked tail queue head. */

So stailhead is a structure

How to pass head and entries to a function?

#define STAILQ_ENTRY(type)                                              \
struct {                                                                \
        struct type *stqe_next; /* next element */                      \
}

So entries and head ( as explained before ) are just structures and you can pass them just as you pass other structures. &structure_variable

What type is head, how can I declare a pointer to it?

Already explained!

Read this man page for nice pretty examples.