OCaml 4.10.0, second beta

The release of OCaml 4.10.0 is near. We have released a second beta
version to help you adapt your softwares and libraries to the new features
ahead of the release.

This new beta contains an update to the internal runtime API that
should make it easier to maintain compatibility across version
for expert users; and a small fix for the analysis of recursive

The source code is available at these addresses:


The compiler can also be installed as an OPAM switch with one of the
following commands.

opam switch create ocaml-variants.4.10.0+beta2 --repositories=default,beta=git+https://github.com/ocaml/ocaml-beta-repository.git


opam switch create ocaml-variants.4.10.0+beta2+\<VARIANT\> --repositories=default,beta=git+https://github.com/ocaml/ocaml-beta-repository.git

where you replace <VARIANT> with one of these:

For a better experience, you can use the opam alpha repository provided by:

opam repository add alpha git://github.com/kit-ty-kate/opam-alpha-repository.git

This repository contains a handful of temporary patched packages, that you can use
while waiting for the packages to be properly patched.
This repository should not be used in production and you probably want to install
it only for the beta switch.

We want to know about all bugs. Please report them here:


Happy hacking.


Did you mean to write “beta2” in those “switch create” lines?

Indeed, this fixed now, thanks!

Could someone please look at these PRs to the ppx_deriving repository? So it will be ready for the upcoming 4.10 release:

And the corresponding ppx_deriving_yojson PRs: