Dear OCaml users,

Last week, we merged an update to the compiler-libs "shape" API for querying

definition information from the compiler in the 5.2 branch of the compiler.

Unfortunately, this small change of API breaks compatibility with at least odoc.
Generally, we try to avoid this changes to the compiler library during the beta

releases of the compiler. However, after discussions, we concluded that it will

be easier on the long term to fix the API right now in order to avoid multiplying

the number of supported versions of the shape API in the various OCaml

developer tools .

We have thus released a second beta version of OCaml 5.2.0 to give the time

to developer tools to update their 5.2.0 version ahead of the release

(see below for the installation instructions).

Beyond this changes of API, the new beta contains three minor bug fixes and three
documentation updates, which is a good sign in term of stability.

As usual, you can follow the last remaining compatibility slags on the
opam readiness for 5.2.0 meta-issue (https://github.com/ocaml/opam-repository/issues/25182).

If you find any bugs, please report them on OCaml's issue tracker (https://github.com/ocaml/ocaml/issues).

Currently, the release is planned for the beginning of May.

If you are interested in full list of features and bug fixes of the new OCaml version, the
updated change log for OCaml 5.2.0 is available on GitHub (https://github.com/ocaml/ocaml/blob/5.2/Changes).

Happy hacking,
Florian Angeletti for the OCaml team.

Installation Instructions
----------------------------

The base compiler can be installed as an opam switch with the following commands
on opam 2.1:

   opam update
   opam switch create 5.2.0~beta2

The source code for the beta is also available at these addresses:

- GitHub: https://github.com/ocaml/ocaml/archive/5.2.0-beta2.tar.gz
- OCaml archives at Inria: https://caml.inria.fr/pub/distrib/ocaml-5.2/ocaml-5.2.0~beta2.tar.gz

Fine-Tuned Compiler Configuration

-----------------------------------------------

If you want to tweak the configuration of the compiler, you can switch to the option variant with:


   opam update
   opam switch create <switch_name> ocaml-variants.5.2.0~beta2+options <option_list>

where `option_list` is a space-separated list of `ocaml-option-*` packages.

For instance, for a `flambda` and `no-flat-float-array` switch:

      opam switch create 5.2.0~beta2+flambda+nffa ocaml-variants.5.2.0~beta2+options ocaml-option-flambda ocaml-option-no-flat-float-array


All available options can be listed with `opam search ocaml-option`.


Changes since the first beta
----------------------------

### Compiler-libs API Changes

- #13001(https://github.com/ocaml/ocaml/issues/13001): do not read_back entire shapes to get aliases' uids when building the
  usages index
  (Ulysse Gérard, review by Gabriel Scherer and Nathanaëlle Courant)

### Bug Fixes

- #13058(https://github.com/ocaml/ocaml/issues/13058): Add TSan instrumentation to caml_call_gc(), since it may raise
  exceptions.
  (Fabrice Buoro, Olivier Nicole, Gabriel Scherer and Miod Vallat)

- #13079(https://github.com/ocaml/ocaml/issues/13079): Save and restore frame pointer across Iextcall on ARM64
  (Tim McGilchrist, review by KC Sivaramakrishnan and Miod Vallat)

- #13094(https://github.com/ocaml/ocaml/issues/13094): Fix undefined behavior of left-shifting a negative number.
  (Antonin Décimo, review by Miod Vallat and Nicolás Ojeda Bär)

### Documentation Updates

- #13078(https://github.com/ocaml/ocaml/issues/13078): update Format tutorial on structural boxes to mention alignment
  questions.
  (Edwin Török, review by Florian Angeletti)

- #13092(https://github.com/ocaml/ocaml/issues/13092): document the existence of the `[@@poll error]` built-in attribute
  (Florian Angeletti, review by Gabriel Scherer)

- #13066(https://github.com/ocaml/ocaml/issues/13066), update OCAMLRUNPARAM documentation for the stack size parameter l
  (Florian Angeletti, review by Nicolás Ojeda Bär, Tim McGilchrist, and Miod Vallat)