We could also use Bytes everywhere and add module Bytes = String for OCaml < 4.02, but that would mean we would have to preprocess every file with camlp4...
So it seems like the nicer option would be to add something like a compat module with bytes_create etc. functions and only preprocess the compat.ml and compat.mli with camlp4...

Is this an ok way to fix the makefile?
rijesha@af911cd

EDIT: probably not. I need to make sure that compat.ml compiles first. Ill work on it a bit more.

Ok so I think I fixed the Makefile. I used a shell if statement to only compile files listed in PP_SRC with the preprocessor. rijesha@81f9dfb

I started to modify the rest of the .ml files.

PPRZLINK will need to be modified. It compiles first so compat.ml will have to be copied into that repo as well and the Makefile will need to be set up for the campl4. Unless there is a better way of doing it?

Thanks for the work @rijeshaugustine !
Can you plz make a pull request?
pprzlink will have to be updated separately...

For pprzlink just adding the compat module to it will cause another warning when building sw/lib/ocaml due to compat.cmo already existing. Can this be rectified by telling the sw/lib/ocaml/Makefile to ignore compat.ml if compat.cmo exits in sw/ext/pprzlink/*/ocaml/ or will that cause other issues in the future?

Just an idea - can we update the ocaml version that is installed with paparazzi (i.e. package update)? That way we wouldn't have to worry about the backward compatibility (<4.02) I suppose? (I am assuming that even older OS like Ubuntu 12.04 can upgrade to the >4.02 Ocaml)

@podhrmic that would be only possible if you manually install a newer OCaml version (from source or via opam)...
Debian (Ubuntu) packages are available in these versions: http://packages.ubuntu.com/search?keywords=ocaml
So 4.02 is only available since latest xenial

What I did for the Debug module is that I just made a specific one for pprzlink with a different name...

made a pull request for pprzlink paparazzi/pprzlink#23

Thanks! closing this as the relevant pull requests have been merged...