Thanks for all you answers, removing all oasis generated and compiled
files didn't help but switching to 4.03.0 without flambda solved the
problem.

I will upload my example on the tracker, mine is really small (37 lines).

On 28/09/2016 20:30, Ivan Gotovchits wrote:
> Can confirm that I've seen the same issues 100% reproducible on
> 4.03+flambda with oasis 0.4.7. Everything worked fine with `<
> oasis.0.4.6`.
>
> I created an issue[1] on the tracker and I also CC'ed the author. It
> would be nice if you, guys, will also upload your examples to the
> issue tracker, so that we can fix it ASAP (mine example is too big its
> an _oasis file that is more than thousand lines of code, I've tried on
> a smaller example, but bug didn't manifest itself). 
>
> [1]: https://forge.ocamlcore.org/tracker/index.php?func=detail&aid=1674&group_id=54&atid=291
>
> On Sun, Sep 25, 2016 at 10:20 PM, Boutillier, Pierre
> <Pierre_Boutillier@hms.harvard.edu
> <mailto:Pierre_Boutillier@hms.harvard.edu>> wrote:
>
>     DISCLAIMER: I don't know anything about oasis.
>     > Le 22 sept. 2016 à 17:37, Yann Hamdaoui <yann.hamdaoui@gmail.com <mailto:yann.hamdaoui@gmail.com>> a écrit :
>     >
>     > I run oasis version 0.4.7 with compiler switch 4.03.0+flambda
>     It seems indeed that oasis.0.4.7 hates 4.03.0+flambda
>     Here is my story:
>     I tried an `opam update` on a debian jessie machine. It had the
>     consequence to attempt an update of `tls`. (`tls` forces an `oasis
>     setup` during its ./configure) it fails with `none: unknown option
>     '--enable-lwt'.`
>     Strange...
>     So I tried to install tls on a MacOS "just to see" (using switch
>     4.03.0+flambda too) There, the compilation of `nocrypto` fails at
>     `oasis setup` with `E: Unknown flag 'modernity'` By random
>     copy/paste I experience that the only way to remove this error is
>     indeed to make `Flag modernity` the last Flag section of the file
>     but in this case other flags seems to be ignored (let's stay
>     factual: --enable-lwt and --disable-xen are unrecognized options)
>
>     Then I remembered about your message and I realized that we were
>     both using +flambda. So I  `opam switch 4.03.0 && opam install
>     tls` ... Success!
>     Finally in my +flambda switch I downgrade oasis to 0.4.6 (on
>     debian because on MacOS this operation was too much for opam
>     internal solver: it suggests something implying `===== ∗  4   ↻ 
>     10   ↘  15   ⊘  18 =====` :-)) Success, I can install tls again!
>
>     I stopped here. I was too happy to be back in a working setting
>     but there is something to investigate...
>
>     All the best,
>     Pierre B.
>
>
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