MPR#5548: ocamlbuild's ocamlfind integration doesn't support syntax extensions

[damiendoligez]

PR transferred from https://caml.inria.fr/mantis/view.php?id=5548
[original reporter: @gasche ]

OCamlbuild's ocamlfind integration includes -I-options and stuff from ocamlfind in the "compile" and "link" ocamlbuild steps but, to my knowledge, does not include them during preprocessing ("pp"). This means that while ocamlfind libraries can be used, I don't know how to use their attached syntax extensions (ocamlfind's predicate "syntax"). It would be nice if that was fixed.

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With some ocamlfind package foo.syntax that enables syntax extensions, and some file test.ml using the extension,

  ocamlfind ocamlc -syntax camlp4o -package foo.syntax test.ml

does not raise a syntax error, while for instance

  ocamlbuild -use-ocamlfind -tag "package(foo.syntax)" test.pp.ml

does (because neither ocamlfind's -I-option nor the camlp4 extension archive name are included in the camlp4o invocation).

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I have discussed this with Anil Madhavapeddy which mentioned a related need on the mailing list:

https://groups.google.com/forum/#!topic/fa.caml/y6VsobyJV0s/discussion