Excerpts from Dario Teixeira's message of Mon Mar 10 16:33:56 +0100 2008:
> > Nice!  Apart  the link with findlib.cma that is not supported yet and could
> > be with  the  multiple-plugins support in ocamlbuild. I think that one can
> > easily build a generic plugin for ocamlfind packages.
> 
> Hi,

Hi,

> 
> I hope so too.  However, note that no one has managed yet to provide a solution
> to my original question, namely of integrating Ocamlbuild with findlib *and*
> camlp4.  Perhaps I should have explained better what this entails:
> 
> Suppose you are using the Sexplib syntax extension.  This syntax extension
> depends on Sexplib itself and on another syntax extension, offered by the
> Type-conv package.  The META package for Sexplib should contain the following:
> (note that the version currently shipping with GODI is incomplete)
> 
> ###############################################################
> name="sexplib"
> version="3.0.0"
> description="Sexplib - automated S-expression conversions"
> requires="bigarray"
> archive(byte)="sexplib.cma"
> archive(native)="sexplib.cmxa"
> 
> package "statements" (
>   requires = "sexplib,type-conv.statements,camlp4"
>   version = "3.0.0"
>   description = "Syntax extension for Sexplib"
>   archive(syntax,preprocessor) = "pa_sexp_conv.cmo"
>   archive(syntax,toploop) = "pa_sexp_conv.cmo"
>   )
> ###############################################################
> 
> 
> To compile with Findlib a data.ml file that makes use of the Sexplib syntax
> extension is very simple.  You just have to specify the "sexplib.statements"
> package, and findlib will *automatically* take care of also loading libraries
> or even other syntax extensions needed by sexplib.statements:
> 
> ocamlfind ocamlc -package sexplib.statements -syntax camlp4o -c data.ml
> 
> 
> Why am I insisting on this?  Because when we manage to integrate these
> three tools, we will essentially have solved the very common request of
> providing easy access to common syntax extensions (just last week there was
> an OSR on this subject).  All that will be required to compile a file such as
> data.ml using the Sexplib syntax extension will be to add a line "<data.ml>:
> use_sexplib.statements" to the _tags file.  You won't even need to create
> a custom Ocamlbuild plugin or anything, because this findlib support could
> be provided by a default plugin (living on $HOME/.ocamlbuild or something).
> So, Nicolas, is this altogether feasible with the current Ocamlbuild?
> (And if so, could you lent us a hand -- you are of course the most
> competent person to do so).

First  I  would  like  thanks  everyone that participated in also helping you.
Keep up!

Currently  we  must  add  a  myocamlbuild.ml  file  in  your  project  because
ocamlbuild  does  not support multiple plugins (allowing $HOME/.ocamlbuild for
instance).

However  one  can  have  a  reusable  myocamlbuild.ml file. Here is a starting
point:

###################################
open Ocamlbuild_plugin
open Command (* no longer needed for OCaml >= 3.10.2 *)

(* these functions are not really officially exported *)
let run_and_read = Ocamlbuild_pack.My_unix.run_and_read
let blank_sep_strings = Ocamlbuild_pack.Lexers.blank_sep_strings

(* this lists all supported packages *)
let find_packages () =
  blank_sep_strings &
    Lexing.from_string &
      run_and_read "ocamlfind list | cut -d' ' -f1"

(* this is supposed to list available syntaxes, but I don't know how to do it. *)
let find_syntaxes () = ["camlp4o"; "camlp4r"]

(* ocamlfind command *)
let ocamlfind x = S[A"ocamlfind"; x]

let _ = dispatch begin function
   | Before_options ->

       (* override default commands by ocamlfind ones *)
       Options.ocamlc   := ocamlfind & A"ocamlc";
       Options.ocamlopt := ocamlfind & A"ocamlopt";
       Options.ocamldep := ocamlfind & A"ocamldep";
       Options.ocamldoc := ocamlfind & A"ocamldoc"

   | After_rules ->

       (* When one link an OCaml library/binary/package, one should use -linkpkg *)
       flag ["ocaml"; "link"] & A"-linkpkg";

       (* For each ocamlfind package one inject the -package option when
       	* compiling, computing dependencies, generating documentation and
       	* linking. *)
       List.iter begin fun pkg ->
         flag ["ocaml"; "compile";  "pkg_"^pkg] & S[A"-package"; A pkg];
         flag ["ocaml"; "ocamldep"; "pkg_"^pkg] & S[A"-package"; A pkg];
         flag ["ocaml"; "doc";      "pkg_"^pkg] & S[A"-package"; A pkg];
         flag ["ocaml"; "link";     "pkg_"^pkg] & S[A"-package"; A pkg];
       end (find_packages ());

       (* Like -package but for extensions syntax. Morover -syntax is useless
       	* when linking. *)
       List.iter begin fun syntax ->
         flag ["ocaml"; "compile";  "syntax_"^syntax] & S[A"-syntax"; A syntax];
         flag ["ocaml"; "ocamldep"; "syntax_"^syntax] & S[A"-syntax"; A syntax];
         flag ["ocaml"; "doc";      "syntax_"^syntax] & S[A"-syntax"; A syntax];
       end (find_syntaxes ());

   | _ -> ()
end
###################################

Then  consider  that  I want to compile yahoo.ml that requires the json-static
syntax extension, plus json-wheel and netclient.

$ cat _tags
<yahoo.*>: pkg_json-static, pkg_netclient, syntax_camlp4o

$ ocamlbuild yahoo.byte -- ocaml
...


Best regards,

[1]: http://martin.jambon.free.fr/yahoo.ml

-- 
Nicolas Pouillard aka Ertai