dhil / ocaml-multicont Goto Github PK

As a follow-up to the discussion at https://discuss.ocaml.org/t/multi-shot-continuations-gone-forever/9072/13, I think the usual resource-management issues inside resumptions apply to resumptions themselves: currently they have to be dropped manually, which prevents us from referring to them inside other resumptions since it becomes impossible to track when they should be freed.

As suggested in the discussion, one solution is to make resumptions purely GC-managed values. To do so, one can represent a resumption either as a heap value obtained by copying a fiber, or as a fiber which is only discontinued by the GC using a finaliser and which is never reinstated/converted back to a continuation. The interface gets simplified by removal of demote, drop and Resumption_already_dropped.

The distinction between linear continuations, which are allowed to own resources, and multi-shot continuations, which are not, could be explained in the documentation, to underline the issues arising from promoting arbitrary continuations.

(cc @gasche)

In upstream, the module EffectHandlers has been renamed to Effect, c.f. ocaml/ocaml@f3f6ee0. The same change needs to be implemented in this library to restore compatibility.

I'm opening this just to track the issue started in kayceesrk/delimcc_of_fxhandler#1

According to @dra27 ocaml/ocaml#12735 could be the culprit

Currently the code makes some assumptions that are only true in native code mode.

This library should be packaged and released on https://github.com/ocaml-multicore/multicore-opam https://github.com/ocaml/opam-repository.

It would be nice to a minimal CI to test the examples both in native and bytecode modes.