Dear OCaml users,

One month and half= after the release of the first alpha for OCaml 5.3.0, the
release of OC= aml 5.3.0 is drawing near.

The internal API of the compiler librarie= s has been frozen, and most core
developer tools support (or will suppor= t soon) the new version of the compiler.

We have thus released a fir= st beta version of OCaml 5.3.0 to help you update
your software and libr= aries ahead of the release (see below for the installation
instructions)= . More information about the whole release process is now available
in t= he compiler repository
(https://github.com/ocaml/ocaml/blob/trunk/releas= e-info/introduction.md).

Compared to the first alpha release, this b= eta contains a few runtime or
typechecker fixes, a handful of fixes for = the runtime event library and other
miscellaneous fixes.

Exceptio= nally, this beta release also introduces a new flag `-keywords` for the
= compiler. This backward compatibility flag aims to help compiling old code = that
are using `effect` as a normal identifier, now that `effect` is a k= eyword in the
new effect handler syntax.

The progresses on stabil= ising the ecosystem are tracked on the
opam readiness for 5.3.0 meta-iss= ue
(https://github.com/ocaml/opam-repository/issues/26596).

The f= ull release is expected in the end of November or beginning of December,see the new prospective calendar
(https://github.com/ocaml/ocaml/blob/t= runk/release-info/calendar.md) for more
information.

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

If you are interested in full list of feature= s and bug fixes of the new OCaml
version, the updated change log for OCa= ml 5.3.0 is available on GitHub
(https://github.com/ocaml/ocaml/blob/5.3= /Changes),

and a short list of the changes since the last alpha = is available below.

Happy hacking,
Florian Angeletti for the OCam= l team.

---
## Installation Instructions

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

```bash
opam update
opam switch create 5.3.0~be= ta1
```

The source code for the beta is also available at these a= ddresses:

* [GitHub](https://github.com/ocaml/ocaml/archive/5.3.0-be= ta1.tar.gz)
* [OCaml archives at Inria](https://caml.inria.fr/pub/distri= b/ocaml-5.3/ocaml-5.3.0~beta1.tar.gz)

### Fine-Tuned Compiler Config= uration

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

```bash
opam update
opa= m switch create <switch_name> ocaml-variants.5.3.0~beta1+options <= option_list>
```

where `option_list` is a space separated list= of `ocaml-option-*` packages. For instance, for a flambda and no-flat-floa= t-array switch:

```bash
opam switch create 5.3.0~beta1+flambda+nf= fa ocaml-variants.5.3.0~beta1+options ocaml-option-flambda ocaml-option-no-= flat-float-array
```

All available options can be listed with `op= am search ocaml-option`.

-------

## Changes since the first a= lpha

### Runtime fixes

- #13502(https://github.com/ocaml/ocam= l/issues/13502): Fix misindexing related to `Gc.finalise_last` that could p= revent
finalisers from being run.
(Nick Roberts, review= by Mark Shinwell)

- #13402(https://github.com/ocaml/ocaml/issues/13= 402), #13512(https://github.com/ocaml/ocaml/issues/13512), #13549(https://g= ithub.com/ocaml/ocaml/issues/13549), #13553(https://github.com/ocaml/ocaml/= issues/13553): Revise bytecode implementation of callbacks
so tha= t it no longer produces dangling registered bytecode fragments.
(= Xavier Leroy, report by Jan Midtgaard, analysis by Stephen Dolan,
= review by Miod Vallat)

- #13520(https://github.com/ocaml/ocam= l/issues/13520): Fix compilation of native-code version of systhreads. Byte= code fields
were being included in the thread descriptors.
&nb= sp; (David Allsopp, review by S=E9bastien Hinderer and Miod Vallat)

= ### Typechecker fixes

- #13579(https://github.com/ocaml/ocaml/issues= /13579), [#13583](https://github.com/ocaml/ocaml/issues/13583): Unsoundness= involving non-injective types + gadts
(Jacques Garrigue, report = by @v-gb,
   review by Richard Eisenberg and Florian Angeletti= )

- #13388(https://github.com/ocaml/ocaml/issues/13388), [#13540](ht= tps://github.com/ocaml/ocaml/issues/13540): raises an error message (and no= t an internal compiler error)
when two local substitutions are in= compatible (for instance `module type
S:=3Dsig end type t:=3D(mod= ule S)`)
(Florian Angeletti, report by Nailen Matschke, review by= Gabriel Scherer, and
Leo White)

### Compiler flag

= - #13471(https://github.com/ocaml/ocaml/issues/13471): add `-keywords <v= ersion?+list>` flag to define the list of keywords
recognized = by the lexer, for instance `-keywords 5.2` disable the `effect`
k= eyword.
(Florian Angeletti, review by Gabriel Scherer)

###= Runtime event library fixes

- #13419(https://github.com/ocaml/ocaml= /issues/13419): Fix memory bugs in runtime events system.
(B. Szi= lvasy and Nick Barnes, review by Miod Vallat, Nick Barnes,
   = Tim McGilchrist, and Gabriel Scherer)

- #13407(https://github.com/oc= aml/ocaml/issues/13407): Add Runtime_events.EV_EMPTY_MINOR
(Thoma= s Leonard)

- #13522(https://github.com/ocaml/ocaml/issues/13522): Co= nfirm runtime events ring is still active after callback.
(KC Siv= aramakrishnan, review by Sadiq Jaffer and Miod Vallat)

- #13529(http= s://github.com/ocaml/ocaml/issues/13529): Do not write to event ring after = going out of stw participant set.
(KC Sivaramakrishnan, review by= Sadiq Jaffer)

### Documentation

- #13424(https://github.com/= ocaml/ocaml/issues/13424): Fix `Gc.quick_stat` documentation to clarify tha= t returned fields
`live_words`, `live_blocks`, `free_words`, and = `fragments` are not zero.
(Jan Midtgaard, review by Damien Dolige= z and KC Sivaramakrishnan)

- #13440(https://github.com/ocaml/ocaml/i= ssues/13440): Update documentation of `Gc.{control,get,set}` to reflect fie= lds
not currently supported on OCaml 5.
(Jan Midtgaard,= review by Gabriel Scherer)

- #13469(https://github.com/ocaml/ocaml/= issues/13469), #13474(https://github.com/ocaml/ocaml/issues/13474), #13535(= https://github.com/ocaml/ocaml/issues/13535): Document that [Hashtbl.create= n] creates a hash table
with a default minimal size, even if [n]= is very small or negative.
(Antonin D=E9cimo, Nick Bares, report= by Nikolaus Huber and Jan Midtgaard,
   review by Florian Ang= eletti, Anil Madhavapeddy, Gabriel Scherer,
   and Miod Vallat= )

### Standard library internal fix

- #13543(https://gith= ub.com/ocaml/ocaml/issues/13543): Remove some String-Bytes conversion from = the stdlib to behave better
with js_of_ocaml
(Hugo Heuz= ard, review by Gabriel Scherer)

### Toplevel fix

- #13263(htt= ps://github.com/ocaml/ocaml/issues/13263), #13560(https://github.com/ocaml/= ocaml/issues/13560): fix printing true and false in toplevel and error
&= nbsp; messages (no more unexpected \#true)
(Florian Angeletti, re= port by Samuel Vivien, review by Gabriel Scherer)

### Compiler inter= nals

- #13391(https://github.com/ocaml/ocaml/issues/13391), [#13551]= (https://github.com/ocaml/ocaml/issues/13551): fix a printing bug with `-ds= ource` when using
raw literal inside a locally abstract type cons= traint
(i.e. `let f: type \#for. ... `)
(Florian Angele= tti, report by Nick Roberts, review by Richard Eisenberg)