Investing in the Future of OCaml: Thanking the 2025 Sponsors

How does a language like OCaml balance continuous innovation with long-term reliability? As one of many core maintainers of the OCaml compiler, Tarides is dedicated to strengthening the foundations and introducing new and improved workflows to the compiler, delivering reliability, performance, and versatility to OCaml users.

This goal is made possible through the continuous evaluation of the state of the compiler, followed by a targeted response, or what we call ‘maintenance work’.

Why is Compiler Maintenance so Important?

Many companies, organisations, and individuals work on the development and maintenance of the compiler. These groups meet to coordinate their efforts and align with the goals, wants, and needs of the wider community. Tarides is part of this group, and our focus is on performing maintenance that contributes to long-term goals such as multicore support, stability through quality assurance and CI processes, improved performance through benchmarking, and bug hunting and bug fixes.

As you can tell, the term ‘maintenance’ covers a whole host of useful work that is critical to the longevity and growth of OCaml. It can be hard to convey just how important maintenance work is, and that’s why we want to thank the stand-out sponsors that support this crucial effort.

In 2025, we received funding from Jane Street, the OCaml Software Foundation OCSF, and FLOSS/Fund. We want to thank them for their generosity and share some of the projects that their support has made possible.

2025 Projects

This (non-exhaustive) list of projects gives you an idea of the kind of work Tarides performs under the maintenance umbrella.

Opam

The source-based OCaml package manager opam is well-known to almost anyone who uses the language. Performing maintenance on opam involves addressing issues submitted by the community, investigating and testing CI tweaks, reviewing packages, and investing time in project and community management. Ensuring the long-term functionality of a workflow not only covers the technical, but also the social aspects of the project.

OCamlformat

OCamlformat is a code formatter that can automatically reformat your code according to a pre-existing profile or a customised profile. It is a highly configurable tool with many options that let users specify their formatting profiles according to their needs.

With every OCaml update, we update OCamlformat to ensure it remains compatible, in addition to regular maintenance like bug fixes, preparing new features, and discussing suggestions.

Relocatable OCaml

The ‘relocatable OCaml’ project also received funding as part of a maintenance effort. It is a recently merged long-term project with the aim of making the OCaml compiler able to be cloned and built on a different switch. Instead of being compiled from source code, it can now be built from pre-compiled binaries and therefore easily ‘moved’ to a new place.

Before the ‘relocatable’ project could be merged, we implemented a ‘test harness’ to accompany the compiler’s new powers. The test harness conducts a variety of – you guessed it – tests on the compiler when it is relocated to ensure that it works in its new location.

Both the PR implementing the test harness and its subsequent review were performed under the maintenance umbrella.

Multicoretests

The sizable ‘multicoretests’ contains property-based tests for the OCaml multicore compiler and runtime. These tests are vital to enabling OCaml 5’s use in production. Ensuring that they are up-to-date, performant, and bug-free is an ongoing work task performed under the maintenance umbrella.

TSan

Data races can happen when data is shared between multiple threads, as it is in multicore and OCaml 5. OCaml supports ThreadSanitizer, or TSAN, a data race detector. With a TSan-enabled compiler, all of the programs are instrumented with calls to the TSan runtime, which will flag any data races it encounters.

TSan support is continuously maintained; it is monitored and updated to address problems and bring improvements. For example, some of the TSan tests were exhibiting ‘flaky’ behaviour – yielding inconsistent and unreliable results. This was addressed by making the error output more deterministic, using a barrier to enforce the same order between the TSan report and the logging lines.

OCaml Manual

The OCaml Manual provides documentation for the language, and part of OCaml maintenance involves updating it whenever something changes. Two of the updates this year include: A new chapter on profiling with Linux’s perf which describes profiling OCaml’s native code inclusive of frame pointers and DWARF CFI. A [new chapter on the native debugger] (https://github.com/ocaml/ocaml/pull/13747), summarising information previously dispersed in many PRs, comments, issues, and people’s heads!

Reviews & Commits

Of course, far from all maintenance work is initiated by our teams at Tarides. A significant chunk of time and effort also goes into reviewing and merging PRs submitted by other developers. Core maintainers help each other out with reviews, keeping the whole operation going.

The PR “Commits for a signature mismatch with TSan” addressed a misnamed function signature resulting in warnings and failed tests. After general discussion and multiple reviews the PR was merged. This is what a lot of maintenance work looks like, offering review and providing input on PRs submitted to the OCaml repo and helping them get over the line.

Looking Ahead

We are continuing our commitment to performing OCaml maintenance in 2026, and look forward to working with the community to keep OCaml ready for new challenges.

You can connect with us on Bluesky, Mastodon, Threads, and LinkedIn or sign up for our mailing list to stay updated on our latest projects. We look forward to hearing from you!