I currently write an linked-list extension for Ruby, not
because I need it, but for practicing on a simple example.

There are some topics, which are only surficially 
covered by README.EXT:

Is the only task of the mark function, I pass over to 
the Data_Wrap_Structure, to call rb_gc_mark for all
elements held by the data structure?

Is it possible to pass over multiple arguments to the 
block using rb_yield or is there some similarly simple
method for this?
(I looked at the hash.c, but it uses a mechanism 
which seems to be internal.)

Can I relay on using FL_USER* (in ruby.h) flags
for my own objects?
(Are they guarateed to exist in future versions...)
 

Thanks, Christian
k