> > > I wish to read the algorithm of gc, and I cannot.
> >
> > The Emacs gc is a simple mark and sweep collector.
>
> Right.
>
> Alin, you can start by reading the node "Garbage Collection" in the
> ELisp manual, and then proceed reading alloc.c, where you will see
> many functions named mark_SOMETHING and then gc_sweep that does the
> sweep stage.  If you want more background before reading the ELisp
> manual, try googling "mark and sweep garbage collection".
>

I have read the mark-sweep algorithm; I know it. However, I do not manage
making the connection with alloc.c.

For example, I cannot understand what kind of objects are kept in every
node of the red-black tree  (in books I never saw gc implemented with
red-black trees). I know that the objects are kept in obarrays. What link
is there between obarrays and red-black tree of gc ?

What happens to a Lisp_Object defined in C code? Is it freed if it is found
by conservative stack algorithm ? What is the link between GCPRO? macros
and the gc ?