Thanks for your suggestion Gabriel! If I change the extension of my parser
to mlypack, ocamlbuild fails to use it correctly:

[gesundheit:~/w/ocaml-r 17:05]$make
ocaml setup.ml -build
Finished, 0 targets (0 cached) in 00:00:00.
+ ocamlfind ocamlc -c -g -package camlp4 -package camlp4.extend -package
camlp4.lib -package camlp4.quotations -package camlp4.quotations.o -syntax
camlp4o -I src/syntax -o src/syntax/r_lang_lexer.cmo src/syntax/
r_lang_lexer.ml
File "src/syntax/r_lang_lexer.mll", line 4, characters 2-22:
Error: Unbound module R_lang_parser_y

It's not clear to me either what the mlypack are supposed to be. I'll try
to patch the non-modular menhir function in ocamlbuild/ocaml_tools.ml as
you suggest.

Thanks again!
ph.

2012/9/20 Gabriel Scherer <gabriel.scherer@gmail.com>

> I'm not familiar with this part of ocamlbuild, but a look at
> ocamlbuild/ocaml_tools.ml suggest that the different rule named
> "menhir_modular" (which creates stuff from a file with extension
> ".mlypack" rather than ".mly", and which I have never used) has a
> slightly more expression -ocamlc option, that includes (T
> ocamlc_tags), which includes in particular the tags for the .mlypack
> file.
>
> You could try to see if, naming your grammar file .mlypack and adding
> a "foo.mlypack: package(camlp4.lib)" to your _tags, you at least get a
> satisfying menhir invocation. From there, you could either find out
> what this "modular menhir" mode is and how to use it in your case, or
> suggest patching ocamlbuild to use this (T ocamlc_tags) also in simple
> menhir invocations.
>
> On Thu, Sep 20, 2012 at 3:45 PM, Philippe Veber
> <philippe.veber@gmail.com> wrote:
> > Dear camlers,
> >
> > I'm currently trying to implement a camlp4 quotation whose contents will
> be
> > parsed using ocamllex and menhir. Everything went unexpectedly well
> until I
> > tried to add antiquotations. Following Tiphaine Turpin's format syntax
> > extension (https://forge.ocamlcore.org/projects/format/), an
> antiquotation
> > is parsed as a token in ocamllex, and this token is defined in my parser
> as:
> >
> > %token <Camlp4.PreCast.Syntax.Ast.expr> EXPR
> >
> > The thing is when I try to compile my project with ocamlbuild I get the
> > following error:
> >
> > [gesundheit:~/w/ocaml-r 14:46]$make
> > ocaml setup.ml -build
> > Finished, 0 targets (0 cached) in 00:00:00.
> > + menhir --ocamlc 'ocamlfind ocamlc -I src/syntax' --infer
> > src/syntax/r_lang_parser_y.mly
> > File "src/syntax/r_lang_parser_y.mly", line 7, characters 40-44:
> > Warning: the token EXPR is unused.
> > File "src/syntax/r_lang_parser_y.mly", line 7, characters 8-38:
> > Error: Unbound module Camlp4
> > ...
> >
> > Now I can easily (but manually) fix this by adding the missing -I option
> for
> > camlp4 libs:
> >
> > [gesundheit:~/w/ocaml-r/_build 15:22]$menhir --ocamlc 'ocamlfind ocamlc
> -I
> > src/syntax -I +camlp4' --infer src/syntax/r_lang_parser_y.mly
> > File "src/syntax/r_lang_parser_y.mly", line 7, characters 40-44:
> > Warning: the token EXPR is unused.
> > [gesundheit:~/w/ocaml-r/_build 15:22]$
> >
> > My question is how do I tell ocamlbuild to add this option directly? I
> fear
> > the response is "you cannot", if I refer to the piece of code in
> ocamlbuild
> > that generates the call to menhir:
> >
> > let menhir mly env build =
> >   let mly = env mly in
> >   let menhir = if !Options.ocamlyacc = N then V"MENHIR" else
> > !Options.ocamlyacc in
> >   Ocaml_compiler.prepare_compile build mly;
> >   Cmd(S[menhir;
> >         A"--ocamlc"; Quote(S[!Options.ocamlc; ocaml_include_flags mly]);
> >         T(tags_of_pathname mly++"ocaml"++"parser"++"menhir");
> >         A"--infer"; Px mly])
> >
> > I fail to see in this function a hook which I could use to inject the
> > missing argument. Would any one know a workaround to use tokens that have
> > hold a value whose type is not defined in the standard library?
> >
> > Cheers,
> >   Philippe.
> >
> >
>