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compatibility with lwt.6 #55

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Merged
raphael-proust merged 6 commits into from
Sep 10, 2026
Merged

compatibility with lwt.6 #55

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213d585
compatibility with lwt.6
raphael-proust Feb 18, 2026
0e2a76b
engine selection is based on lwt reporting its engine
raphael-proust Feb 18, 2026
048634d
incompatible with lwt<6
raphael-proust Feb 18, 2026
ce8acf6
suppress method override warning in engine's id
raphael-proust Sep 8, 2026
f1b5744
opam constraint for lwt: 5.10
raphael-proust Sep 8, 2026
3b7fcdd
prelude: fix log emission when checking lwt engine
raphael-proust Sep 10, 2026
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5 changes: 3 additions & 2 deletions devkit.opam
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Original file line number Diff line number Diff line change
Expand Up @@ -17,11 +17,12 @@ depends: [
"ounit2"
"camlzip"
"libevent" {>= "0.8.0"}
"ocurl" {>= "0.7.2"}
"curl" {>= "0.10.0"}
"curl_lwt"
"pcre2" {>= "8.0.3"}
"trace" {>= "0.12"}
"extunix" {>= "0.1.4"}
"lwt" {>= "5.7.0"}
"lwt" {>= "5.10"}
"lwt_ppx"
"base-bytes"
"base-unix"
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5 changes: 5 additions & 0 deletions lwt_engines.ml
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Expand Up @@ -30,13 +30,18 @@ method poll fds timeout =
l
end

type Lwt_engine.engine_id += Engine_id__Devkit_libevent

(** libevent-based engine for lwt *)
class libevent =
let once_block = Ev.[ONCE] in
let once_nonblock = Ev.[ONCE;NONBLOCK] in
object(self)
inherit Lwt_engine.abstract

(* suppressing warning 7: for compatibility with both lwt.5.10 and lwt.6
once we move fully to lwt.6 and drop compat with 5.10, we can remove the attribute *)
method[@warning "-7"] id = Engine_id__Devkit_libevent
val events_ = Ev.init ()
val mutable pid = Unix.getpid ()
method events =
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12 changes: 10 additions & 2 deletions prelude.ml
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Expand Up @@ -61,6 +61,14 @@ let call_me_maybe f x =
and poll is guaranteed to be available without the fd limitation.
*)
let () =
if not (Lwt_config._HAVE_LIBEV && Lwt_config.libev_default) then begin

@rr0gi rr0gi Mar 9, 2026

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is this method not available in lwt 6?

@raphael-proust raphael-proust Mar 14, 2026

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it is available

is the concern that then we don't have a version of devkit that's compatible with both 5.9 and 6 so it makes the upgrade for users more difficult? if that's the case then i have ocsigen/lwt#1106 in the works to allow specifically for that

@rr0gi rr0gi Mar 19, 2026

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yes, would prefer to be less disruptive

match Lwt_engine.id () with
| Lwt_engine.Engine_id__libev _ -> ()
| Lwt_engine.Engine_id__select ->
(* prefer poll over select, because select can only monitor fds up to 1024,
and poll is guaranteed to be available without the fd limitation. *)
eprintfn "Switching Lwt engine from select to poll to avoid fd limitations";
Lwt_engine.set @@ new Lwt_engines.poll
end
| Lwt_engine.Engine_id__poll -> ()
Comment on lines +65 to +71

@rr0gi rr0gi May 12, 2026

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Suggested change
| Lwt_engine.Engine_id__libev _ -> ()
| Lwt_engine.Engine_id__select ->
(* Otherwise, prefer poll over select, because select can only monitor fds up to 1024,
and poll is guaranteed to be available without the fd limitation. *)
Lwt_engine.set @@ new Lwt_engines.poll
end
| Lwt_engine.Engine_id__poll -> ()
| Engine_id__libev _ -> ()
| Engine_id__select ->
(* Otherwise, prefer poll over select, because select can only monitor fds up to 1024,
and poll is guaranteed to be available without the fd limitation. *)
Lwt_engine.set @@ new Lwt_engines.poll
| Engine_id__poll -> ()

| _ ->
(* unknown engine*)
()
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