Dear OCaml users,

After two alpha releases, the release of OCaml 5.1.0 is drawing near.
We have thus released a first beta version of OCaml 5.1.0 to help you updat= e your softwares and libraries ahead of the release (see below for the inst= allation instructions).

Compared to the last alpha release, this beta contains two subtle internal = runtime fixes, and one Windows fix.
Overall, the opam ecosystem looks in a good shape for the first beta releas= e.

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

Nearly all core development tools supports OCaml 5.1.0, and you can follow = the last remaining wrinkles on the
opam readiness for 5.1.0 meta-issue: https://github.com/ocaml/opam-reposito= ry/issues/23669.

Currently, the release is planned for the end of July or the beginning of A= ugust.

If you are interested in full list of features and bug fixes of the new OCa= ml version, the
updated change log for OCaml 5.1.0 is available on GitHub: https://github.c= om/ocaml/ocaml/blob/5.1/Changes.

Happy hacking,
Florian Angeletti for the OCaml team.

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

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

   opam update
   opam switch create 5.1.0~beta1

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

* GitHub: https://github.com/ocaml/ocaml/archive/5.1.0-beta1.tar.gz
* OCaml archives at Inria: https://caml.inria.fr/pub/distrib/ocaml-5.1/ocam= l-5.1.0~beta1.tar.gz

Fine-Tuned Compiler Configuration
----------------------------------------------

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

    opam update
    opam switch create <switch_name> ocaml-variants.5.= 1.0~beta1+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 5.1.0~beta1+flambda+nffa ocam= l-variants.5.1.0~beta1+options ocaml-option-flambda ocaml-option-no-fla= t-float-array

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

Changes since the last alpha release:
--------------------------------------------------

### Runtime System Bugfix

- [#12037](https://github.com/ocaml/ocaml/issues/12037): Fix some da= ta races by using volatile when necessary
    (Fabrice Buoro and Olivier Nicole, review by Guillaume M= unch-Maccagnoni,
    Gabriel Scherer and Luc Maranget)

- [#12253](https://github.com/ocaml/ocaml/issues/12253), [#12342](ht= tps://github.com/ocaml/ocaml/issues/12342): Fix infinite loop in signal han= dling.
    (Guillaume Munch-Maccagnoni, report by Thomas Leonard, r= eview by
     KC Sivaramakrishnan and Sadiq Jaffer)

### Windows Bugfix

- [#12184](https://github.com/ocaml/ocaml/issues/12184), [#12320](ht= tps://github.com/ocaml/ocaml/issues/12320): Sys.rename Windows fixes on dir= ectory corner cases.
    (Jan Midtgaard, review by Anil Madhavapeddy)