Hello,

More
> generally, is there a specification of the notion of root used by the
> garbage collector somewhere ?

I recommend you the following article. You should find what you want inside.

@inproceedings{DBLP:conf/ml/CuoqD08,
   author    = {Pascal Cuoq and
                Damien Doligez},
   title     = {Hashconsing in an incrementally garbage-collected system:
                a story of weak pointers and hashconsing in ocaml 3.10.2},
   booktitle = {ML},
   year      = {2008},
   pages     = {13-22},
   ee        = {http://doi.acm.org/10.1145/1411304.1411308},
   crossref  = {DBLP:conf/ml/2008},
   bibsource = {DBLP, http://dblp.uni-trier.de}
}

Hope this helps,
Julien Signoles
-- 
Researcher-engineer
CEA LIST, Software Reliability Lab
91191 Gif-Sur-Yvette Cedex
tel:(+33)1.69.08.71.83  fax:(+33)1.69.08.83.95  Julien.Signoles@cea.fr