Dear Caml riders,

I am trying to access C++ code from OCaml.  I have read
http://caml.inria.fr/Hump/msg778-782 but then this message uses the
interface prior to OCaml 3.00 so I have been trying to rewrite the
example using custom blocks (also to eventually have the added sugar
of comparison,...).  It sort of work; I have problems with the Garbage
Collector giving me a Segmentation fault.  The code is attached below.
If somebody is kind enough to have a look at the files and to point to
me the mistake I made I will be very grateful.

I also want to take opportunity of this message to mention another
problem I met.  To avoid name collisions, it is sometimes desirable to
use a private namespace for Caml .h files, e.g.:

namespace ml {
    extern "C" {
#include <caml/mlvalues.h>
#include <caml/alloc.h>
#include <caml/custom.h>
#include <caml/memory.h>
#include <caml/fail.h>
    }
}

This however has two consequences:

* Some macros do not work anymore since the namespace is not
  "propagated" into the macros definitions.  As a consequence, lost of
  macros need to be redefined which is not robust w.r.t. software
  upgrades...

* One must know what is a macro and what if a function: for example on
  must write ml::value, ml::alloc_custom, and
  ml::custom_serialize_default but one stays with Field, String_val,
  and custom_deserialize_default

Maybe future versions of the header files could solve this problem by
adding automatically a prefix/namespace for C++ compilation, making
everything a macro and making the macros compatible with the prefix
(or maybe there is a better solution ?).

Cheers,
ChriS