I was also under the impression that ocamlbuild Ocamlfind integration was
unable to use archive(syntax) or archive(preprocessor) dependencies for
ocamlfind packages providing syntax extensions. This is a serious
limitation as it makes some ocamlfind packages unusable. If you're
considering improving this, I thank you in advance.

> I took a look at adding support for this into ocamlbuild (when
-use-ocamlfind is specified), but I couldn't spot any way to get ocamlfind
to output the syntax options.

I'm not sure what you're looking for exactly. If you whish to know what
archives should be included at the preprocessing step, this is done using
the "-predicates" option with, say, "-predicates syntax,preprocessor",
which will gives you the archives included in this situation:

  % ocamlfind query -predicates syntax,preprocessor -format '%A' type-conv
  pa_type_conv.cma

> Does everyone else manually run the camlp4o command when using syntax
extensions like type-conv or pa_lwt?

This is useful for debugging purposes, and for some (minor) modes of use of
Camlp4. However, for most Camlp4 development, this has the severe downside
of losing the location information of the original file, if I understand
correctly. This means that you don't want to use it as a transparent step
towards compilation, but only in exceptional situations where the
developers will re-edit the output code.

On Sat, Dec 31, 2011 at 12:19 AM, Anil Madhavapeddy <Anil@recoil.org> wrote:

> There's a very useful %.pp.ml target in OCamlbuild that runs the source
> through camlp4 and outputs the result.  This doesn't work when ocamlfind is
> used, as it includes the -pp flags within the ocamlfind invocation.
>
> I took a look at adding support for this into ocamlbuild (when
> -use-ocamlfind is specified), but I couldn't spot any way to get ocamlfind
> to output the syntax options.
>
> I just wanted to check that this is all in fact true, since it requires
> patching ocamlbuild, findlib, and oasis to make it work. Does everyone else
> manually run the camlp4o command when using syntax extensions like
> type-conv or pa_lwt?
>
> -anil
>
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