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Controlling module loading order.
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Date: -- (:)
From: Gerd Stolpmann <gerd@g...>
Subject: Re: [Caml-list] Controlling module loading order.
Hi Guillaume,

if you want to control from findlib that a certain function is invoked,
the usual way to do it is to put a .cmo/.cmx file into the "archive"
variables. The problem is that the linker drops all unused modules
from .cma/.cmxa archives, and as a consequence the initialization code
of these modules is not executed. So you could make R.interpreter
a .cmo/.cmx - in this case the module is always initialized.

The other workaround is to provide an init function in R.interpreter
like

let init() = ()

By calling this function the user references the interpreter, and all
the initialization code is executed.

Gerd

Am Freitag, den 08.01.2010, 21:54 +0100 schrieb Guillaume Yziquel:
> Hi.
> 
> I've been reimpleminting the OCaml-R binding, and implemented a simple 
> wrapper around the Quantmod package in R:
> 
> http://yziquel.homelinux.org/gitweb/?p=ocaml-r.git;a=tree
> http://yziquel.homelinux.org/gitweb/?p=ocamlr-quantmod.git;a=tree
> 
> Testing these modules from the toplevel is quite fine. However, when 
> compiling stuff using these pieces of code, I have issues with the way 
> the modules are loaded, since the order in which they are loaded has 
> side-effects: Initialisation of the R interpreter in the good case, 
> segfaults in the bad case...
> 
> For instance, the META file of OCaml-R:
> 
> >    1 name = "R"
> >    2 version = "0.2"
> >    3 description = "R bindings for OCaml"
> >    4 requires = "unix"
> >    5 archive(byte) = "r.cma"
> >    6 archive(native) = "r.cmxa"
> >    7 
> >    8 package "interpreter" (
> >    9   version = "0.2"
> >   10   description = "Embedded R interpreter"
> >   11   requires = "R"
> >   12   archive(byte) = "oCamlR.cma"
> >   13   archive(native) = "oCamlR.cmxa"
> >   14 )
> 
> The stub functions are in package "R", and package "R.interpreter" 
> contains a module with and empty signature, whose side-effects are to 
> initialise the R interpreter through an application of the functor
> 
> >   19 module Interpreter (Env : Environment) : Interpreter = struct
> >   20 
> >   21   let () = init ~name: Env.name
> >   22                 ~argv: Env.options
> >   23                 ~env:  Env.env
> >   24                 ~sigs: Env.signal_handlers
> >   25                 ()
> >   26 
> >   27 end
> 
> My issue concerns the Quantmod wrapper: How can I make sure that when 
> the Quantmod module is loaded, the OCamlR module of the "R.interpreter" 
> findlib package gets loaded before?
> 
> Currently the ocamlbuild _tags file for ocamlr-quantmod is
> 
> >    1 <quantmod.ml>: pkg_R.interpreter, pkg_CRAN-zoo
> 
> But that doesn't seem to do the trick...
> 
> My question is: do I have to put a line like "module X = OCamlR" in 
> quantmod.ml, or is there a way to load OCamlR beforehand just by 
> tweaking the build process, order of modules when linking, etc...
> 
> All the best,
> 
-- 
------------------------------------------------------------
Gerd Stolpmann, Bad Nauheimer Str.3, 64289 Darmstadt,Germany 
gerd@gerd-stolpmann.de          http://www.gerd-stolpmann.de
Phone: +49-6151-153855                  Fax: +49-6151-997714
------------------------------------------------------------