OCaml 5.00 compatibility

[patricoferris]

OCaml 5.00 (at the moment trunk) has removed lots of functions that were deprecated including String.uppercase that is used in the unix library's discover executable.

lwt/src/unix/config/discover.ml

Line 67 in 1b123ff

let uppercase = String.uppercase [@ocaml.warning "-3"]

This needs fixed so lwt can be installed with OCaml 5.00. I have a fix here which aimed to keep things working on 4.02 (I think uppercase_ascii was added in 4.03). By the looks of it, lwt supports 4.02 but isn't tested against it so maybe there's a plan to drop support, in which case uppercase_ascii would probably suffice?

EDIT: I just noticed there are tests for 4.02 and they fail for my "fix" because an older version of dune is used. It probably needs something like https://github.com/janestreet/result? At any rate the issue still stands :))

[EduardoRFS]

There is also the problem of Unix.fork on Lwt_process, which I guess could be replaced by create_process.

[raphael-proust]

@EduardoRFS Is the issue that we can't use Unix.fork at all when we have domains spawned? How is create_process handled under the hood in 5.00?

[EduardoRFS]

@raphael-proust yes that's the issue. Unix.create_process uses spawn which is implemented in C directly https://github.com/ocaml/ocaml/blob/trunk/otherlibs/unix/unix.ml#L894

But that doesn't work as Lwt_process actually cannot be described on create_process because there is no way to close fd's on the child process, so this line cannot be implemented. https://github.com/ocsigen/lwt/blob/master/src/unix/lwt_process.ml#L159

And this changes behavior considerably, so likely lwt will need to implement it's own spawn in C. Like https://github.com/ocaml/ocaml/blob/trunk/otherlibs/unix/spawn.c#L31

[patricoferris]

If I understand correctly, I think something needs done with the bigarray library in lwt.unix too. The ocamlfind package is gone from 5.00 so on a 5.00.0+trunk switch it would seem lwt.unix will be hidden because it is optional and has unmet dependencies.

[raphael-proust]

Lwt is now OCaml.5-compatible. Closing.

[EduardoRFS]

It doesn't seems to have solved my problem at least from looking at code.

Lwt_process still calls Lwt_unix.fork

lwt/src/unix/lwt_process.cppo.ml

Line 153 in fbd4fc5

match Lwt_unix.fork () with

Which calls Unix.fork https://github.com/ocsigen/lwt/blob/master/src/unix/lwt_unix.cppo.ml#L2307

Which then will fail at
https://github.com/ocaml/ocaml/blob/trunk/otherlibs/unix/fork.c#L41

[raphael-proust]

@EduardoRFS I have opened a separate issue to track this problem.