OCaml Weekly News

Hello

Here is the latest OCaml Weekly News, for the week of October 29 to Novembe= r 05, 2024.

GPTar 1.0.0

Archive: ht= tps://discuss.ocaml.org/t/ann-gptar-1-0-0/15527/1

Reynir Bj=C3=B6rnsson announced

I am pleased to announce GPTar<= /a> 1.0.0!

GPTar is a small library to create a tartition table, that is, a tar= archive that also contains a valid GUID partition table (GPT).

It exploits the fact that the important areas of a protective MBR in GPT an= d a tar header are mostly disjoint. The tar header fits almost exactly in t= he boot strap code of a master boot record (MBR) with the last 54 bytes of = the tar header overlapping with the partition table of the (protective) MBR= . Thakfully, those are the 54 last bytes of the 155 byte long NUL terminate= d "filename prefix" of the tar header. So as long as we put a NUL byte befo= re the partition table tar will happily ignore the partition table data.

To further hide the actual GPT header & partition table from tar utilit= ies the first tar header uses the GNU volume header extension with the GPT = header & partition table as the "file contents". This makes GNU tar lis= t the volume header but when extracting files the volume header is skipped.= For released versions of bsdtar this unfortunately results in a "ba= d archive" error - however, the as-yet unreleased libarchive/bsdtar fixes t= his "bug" and allows for this abuse of volume headers (see the "update" blo= g post).

For more in depth details you may be interested in reading the following tw= o blog articles:

Why!?

Great question. At Robur we developed a= n opam-mirror uni= kernel that acts as an opam repository and package source archive cache sim= ilar to https://opam.ocaml.org/. Th= ere we use tar as a filesystem for the package source archive cache. Later,= we started using the end of the block device to cache data such as git sta= te and computed package source archive checksums.

The neat feature is we could use regular old bsdtar or GNU tar in the host = system to inspect the tar filesystem data. The downside was the lack of a p= artition table using offsets provided by boot arguments for where to find t= he cached data. With GPTar we can have both! Inspect the tar filesystem dat= a while being more robust with a partition table.

Also, it was very fun to develop.

opam 2.3.0~rc1

Archive: https://discuss.ocaml.org/t/ann-opam-2-3-0-rc1/15533/1

Kate announced

We're happy to announce the first and hopefully only release candidate of o= pam 2.3.0.

This version does not have any significant change compared to the previous = 2.3.0~beta2 release and we hope the final release to also have no significant change. Regardless, we invite users to test this version to make sure there isn't a= ny regressions.

Unless a regression is spotted or another problem arises, we hope to have t= he final release of 2.3.0 out on the 12th of November.

Try it!

The upgrade instructions are pretty much the same:

For Unix systems

bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh) --version 2.=
3.0~rc1"

or from PowerShell for Windows systems

Invoke-Expression "& { $(Invoke-RestMethod https://opam.ocaml.org/insta=
ll.ps1) } -Version 2.3.0~rc1"

Please report any issues to the bug-tracker.

Call for Contributions: BOB 2025 (Berlin, March 14 - Deadline = Nov 15)

Archive: https://discuss.ocaml.org/t/c= all-for-contributions-bob-2025-berlin-march-14-deadline-nov-15/15371/2

Later in this thread, Michael Sperber announced

OCaml content is most welcome at BOB - send us your proposal!

First beta release for OCaml 5.3.0

Archive: https://discuss.ocaml.org/t/first-beta-release-for-ocaml-5= -3-0/15551/1

octachron announced

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

The internal API of the compiler libraries has been frozen, and most core d= eveloper tools support (or will support soon) the new version of the compil= er.

We have thus released a first beta version of OCaml 5.3.0 to help you updat= e your software and libraries ahead of the release (see below for the insta= llation instructions). More information about the whole release process is = now available in the compiler repository.

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

Exceptionally, 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= keyword in the new effect handler syntax.

The progresses on stabilising the ecosystem are tracked on the opam readiness for 5.= 3.0 meta-issue.

The full release is expected in the end of November or beginning of Decembe= r, see the new prospective calendar for more information.

If you find any bugs, please report them on OCaml's issue tracker.

If you are interested in full list of features and bug fixes of the new OCa= ml version, the updated change log for OCaml 5.3.0 is available on GitHub and a short = list of the changes since the last alpha is available below.

Installation Instructions

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

opam update
opam switch create 5.3.0~beta1

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

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.5.3.0~beta1+options &=
lt;option_list>
```
where option_list is a space separated list of ocaml-opt= ion-* packages. For instance, for a flambda and no-flat-float-array = switch:
```
opam
```
switch create 5.3.0~beta1+flambda+nffa ocaml-variants.5.3.0~beta1+options o= caml-option-flambda ocaml-option-no-flat-float-array

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




Changes since the first alpha



Runtime fixes



#13502: Fix=
 misindexing related to Gc.finalise_last that could prevent
finalisers from being run.
(Nick Roberts, review by Mark Shinwell)
#13402, #13512, #13549, #13553: Revise bytecode implemen=
tation of callbacks
so that it no longer produces dangling registered bytecode fragments.
(Xavier Leroy, report by Jan Midtgaard, analysis by Stephen Dolan,
 review by Miod Vallat)
#13520: Fix=
 compilation of native-code version of systhreads. Bytecode fields
were being included in the thread descriptors.
(David Allsopp, review by S=C3=A9bastien Hinderer and Miod Vallat)




Typechecker fixes



#13579, #13583: Unsoundnes=
s involving non-injective types + gadts
(Jacques Garrigue, report by @v-gb,
 review by Richard Eisenberg and Florian Angeletti)
#13388, #13540: raises an =
error message (and not an internal compiler error)
when two local substitutions are incompatible (for instance module ty=
pe S:=3Dsig end type t:=3D(module S))
(Florian Angeletti, report by Nailen Matschke, review by Gabriel Scherer, a=
nd
Leo White)




Compiler flag



#13471: add=
 -keywords <version?+list> flag to define the list of ke=
ywords
recognized by the lexer, for instance -keywords 5.2 disable th=
e effect
keyword.
(Florian Angeletti, review by Gabriel Scherer)




Runtime event library fixes



#13419: Fix=
 memory bugs in runtime events system.
(B. Szilvasy and Nick Barnes, review by Miod Vallat, Nick Barnes,
 Tim McGilchrist, and Gabriel Scherer)
#13407: Add=
 Runtime_events.EV_EMPTY_MINOR
(Thomas Leonard)
#13522: Con=
firm runtime events ring is still active after callback.
(KC Sivaramakrishnan, review by Sadiq Jaffer and Miod Vallat)
#13529: Do =
not write to event ring after going out of stw participant set.
(KC Sivaramakrishnan, review by Sadiq Jaffer)




Documentation



#13424: Fix=
 Gc.quick_stat documentation to clarify that returned fields
live_words, live_blocks, free_words,=
 and fragments are not zero.
(Jan Midtgaard, review by Damien Doligez and KC Sivaramakrishnan)
#13440: Upd=
ate documentation of Gc.{control,get,set} to reflect fields
not currently supported on OCaml 5.
(Jan Midtgaard, review by Gabriel Scherer)
#13469, #13474, #13535: Document that [Ha=
shtbl.create n] creates a hash table
with a default minimal size, even if [n] is very small or negative.
(Antonin D=C3=A9cimo, Nick Bares, report by Nikolaus Huber and Jan Midtgaar=
d,
 review by Florian Angeletti, Anil Madhavapeddy, Gabriel Scherer,
 and Miod Vallat)




Standard library internal fix



#13543: Rem=
ove some String-Bytes conversion from the stdlib to behave better
with js_of_ocaml
(Hugo Heuzard, review by Gabriel Scherer)




Toplevel fix



#13263, #13560: fix printi=
ng true and false in toplevel and error
messages (no more unexpected #true)
(Florian Angeletti, report by Samuel Vivien, review by Gabriel Scherer)




Compiler internals



#13391, #13551: fix a prin=
ting bug with -dsource when using
raw literal inside a locally abstract type constraint
(i.e. let f: type #for. ...)
(Florian Angeletti, report by Nick Roberts, review by Richard Eisenberg)







dune 3.16


Archive: http=
s://discuss.ocaml.org/t/ann-dune-3-16/14889/2




Etienne Marais announced


We have release 3.16.1. This is a minor release of Dune to correct a bug re=
lated to the C++ compile. It comes with the following changes:




3.16.1 (2024-10-30)



Fixed



Call the C++ compiler with -std=3Dc++11 when using OCaml &=
gt;=3D 5.0
(#10962, @kit-ty-kate)












Other OCaml News



From the ocaml.org blog


Here are links from many OCaml blogs aggregated at the ocaml.org blog.



Making Crypto Safer: Introducing the ARGOS Proje=
ct
Postes=
, t=C3=A9l=C3=A9graphes et t=C3=A9l=C3=A9phones, next steps
GPTar (u=
pdate)









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Alan Schmitt

OCaml Weekly News

Table of Contents

GPTar 1.0.0

Reynir Bj=C3=B6rnsson announced

Why!?

opam 2.3.0~rc1

Kate announced

Try it!

Call for Contributions: BOB 2025 (Berlin, March 14 - Deadline = Nov 15)

Later in this thread, Michael Sperber announced

First beta release for OCaml 5.3.0

octachron announced

Installation Instructions

Changes since the first alpha

dune 3.16

Etienne Marais announced

3.16.1 (2024-10-30)

Other OCaml News

From the ocaml.org blog

Old CWN