Dune and camlp4/camlp5 (actually, "dune and the -pp flag to ocamlc"

[up front: I’m not -complaining; rather, I’m just -verifying- that this is the current state of affairs.]
Hi, I’ve been digging around, and I can’t find any indication of support for camlp4/camlp5 in dune. To wit, I don’t find any indication of a way to specify “-syntax” to ocamlfind, nor a way to specify “-pp” to the ocamlc commandline.

Again: I can fully understand why these capabilities are not present; I just want to verify that that’s the case, and that I"m not overlooking something obvious.

ETA: ah, I see I can pass raw “-pp” flags to ocamlc. That’ll probably be enough for my purposes.

I think you can consider it as a preprocess step and even enable it only on some files

  (preprocess
    (per_module
      ((action (run camlp4o %{input-file})) your_module)))

Oh, nice! Thank you for the pointer! I’m not a dune user: I use makefiles and autoconf, b/c “too much C/C++ code in my projects”.

In GT we needed some hacking to extract right ocamlfind options to substitute them to camlp5 call

I’m curious what you meant by this. Can you explain a little? Perhaps you mean

when you have a compile-command that uses ocamlfind, and you want to instead produce the equivalent camlp5 command, you have to do a little work to figure out what arguments to camlp5 are required to get the same effect as what ocamlfind does internally.

Is that what you meant?

yes, exactly. I can link you dune config scripts if you need this

Oh, that’d be very useful. Thank you!

you can look at this repo: https://github.com/kakadu/ocanren/tree/dune