OCaml Weekly News

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Here is the latest OCaml Weekly News, for the week of January 24 to 31, 2023.

Table of Contents

Stramon 0.2.2 - Process behavior monitoring utility based on strace

Darren announced

I’m happy to announce Stramon (right now mainly distributed as statically built binary here).

Stramon is primarily created to make usage of strace and the analysis of strace output easier.

Stramon invokes strace underneath, analyzes the piped output and summarizes the findings into a JSON file when the command finishes.

An example JSON created by running Firefox via Stramon can be seen here. (Network access section is trimmed.)

Diskuv OCaml 1.2.0 (Windows, MSVC)

jbeckford announced

There is a new release of the Diskuv OCaml installer available for Windows users at https://github.com/diskuv/dkml-installer-ocaml/releases/tag/v1.2.0. It contains critical changes that were blocking some Windows users from completing the install, and some performance improvements thanks in large part to @edwin. The release notes have been reproduced immediately below. It will be available using winget install Diskuv.OCaml in a week or so.

Upgrading? First uninstall the old Diskuv OCaml version using “Add or remove programs” in the Control Panel.

Callout to VirtualBox users: You’ll need a workaround for a not-yet backported FMA fix by doing the following in a PowerShell terminal inside VirtualBox before running the installer:

mkdir "$env:ProgramData\DiskuvOCaml\conf\"
Set-Content -Path "$env:ProgramData\DiskuvOCaml\conf\ocamlcompiler.sexp" -Value "((feature_flag_imprecise_c99_float_ops))"

Critical changes:

  • Switch from the official MSYS2 msys2-base install, plus a set of MSYS2 Internet updates, to a standalone msys2-dkml-base that has all the MSYS2 packages needed during installation. That removes the Internet, GPG keys, proxies, etc. as a source of failures during the MSYS2 sub-installation.
  • Special handling for Scoop package manager on Windows which comingles a conflicting bash.exe and git.exe in the same directory. A prior scoop install git should no longer present a problem during installation.
  • Fixed: No longer need to do opam pin remove ... to install merlin and ocaml-lsp.

Performance improvements:

  • Plumb the number of cpus to the compiler jobs. [@edwin]
  • Skip over cross-compiling support when no target ABIs specified.
  • Overall shaved ~15 minutes from installation on a 3-CPU machine (80m instead of 95m), with additional savings if you have more CPUs. Timings in https://github.com/diskuv/dkml-runtime-common/pull/1

Open source help wanted:

  • Byte-code only installation. That will be fast and simple and light, and is likely the best option for students. The existing installer already ships with a functioning ocamlrun and standard library, and is “component”-based so pieces can be added or removed. No Visual Studio, no MSYS2, no spending time compiling code during installation. However a shim would need to be developed so that ocaml, ocamlc, utop, etc. work without setting required OCaml environment variables. Almost all of this new byte-code only installation can be developed on macOS or Linux. If you would like to contribute post your github username on https://github.com/diskuv/dkml-installer-ocaml/issues/35

Component upgrades:

  • Bump utop from 2.9.0 to 2.10.0.
  • ocurrent ocaml/opam CI Docker image (a source of pins) updated from 2022-02-28 to 2022-11-22; numerous pins updated.

Bug fixes:

  • dkml-runtime-common-native works with spaces in the Windows home directory
  • Removed incorrect ptime.0.8.6 pin during dkml init; now ptime.1.1.0

Doc fixes:

  • Create dune-project in Beyond Basics documentation alongside existing dune init exe to adhere to Dune 3.x behavior. (Dune 3.6 was added in DKML 1.1.0)


  • The dkml --build-type build type option will be removed next release. It was originally created for Linux builds (perf and AFL variants), and can be resurrected and simplified if and when Linux support is added.

Internal changes:

  • Added Jane Street’s base package to global utop. In particular, base is now part of the dkml switch created during installation. core is too expensive (52 packages) to install automatically, but you can install utop and core in your own switch. For now this is not that useful. The lib/stublibs directory of the dkml switch needs to be in the PATH for #require "base";; to work in global utop. That would help readers of the Real World OCaml book. A future release will automate the PATH change.
  • Removed digestif.1.1.2+msvc pin since MSVC changes upstreamed to 1.1.3.
  • The bytecode *.bc embedded in the installer is compiled with 4.14.0 and its embedded runtime is also 4.14.0.
  • When using opam option setenv+= stop removing the environment file to force a rebuild of the environment.
  • Pin omd.1.3.1
  • Print timestamp for many logging operations to aid performance comparisons


Simple installation of packages without network

Anthony Scemama announced

I have access to machines that don’t allow me to download anything from the web, so I had difficulties installing software with Opam. With the help of Raja from OCamlPro, I came to a practical solution that solved my problem, and I turned it into a script: https://github.com/scemama/OpamPack It is a simple script that makes a tar.gz on your local machine with all the dependencies you need, and then you can copy the tar.gz o the remote isolated machine and install everything using Opam without needing the network.


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