David Allsopp’s blog featuring musings on O(x)Caml, Windows and other vaguely-related things. Views expressed are my own, rather than my employer’s.
On 16 December 2000, a young @dra1 stepped out on to the stage of St Martin-in-the-Fields making what would be the first of many performances of Johann Sebastian Bach’s great Mass in B minor. On 16 November last year, just under 25 years later, a slightly greyer @dra27 stepped out on the stage of King’s Hall at Newcastle University for what, for now at least2, would be his last performance of this…
The spring-cleaning continues! When I originally prototyped Relocatable OCaml, it was during the OCaml 4.13 development cycle. The focus for the work originally was always about multiple versions of the compiler co-existing without interfering with each other, so even the early prototypes were done on both OCaml 4.12 and OCaml 4.13. In fact, I see that in this talk, I even demo’d it on both…
As we settle into 2026, I have been doing a little early spring-cleaning. A few years ago, we had a slightly chaotic time in opam-repository over what should have been a migration from gforge.inria.fr to a new GitLab instance. Unfortunately, some release archives effectively disappeared from official locations, and although the content was available elsewhere, the precise archives weren’t…
As I was very happy to announce on Discuss on 12 December, OCaml is Relocatable! Today, the final piece of the puzzle was merged, which is the necessary support to allow opam to take advantage of all this to be able to clone switches instead of recompiling them. Before this, you could rename a local switch, for example, but opam would still be compiling them from scratch. The fruits of this…
Someone was kind enough a few weeks ago to comment on Hacker News that “Opam on Windows is a masterpiece of engineering”. There’s certainly a lot which has to go on under the hood to create what I believe is the necessary baseline experience. Unfortunately, it doesn’t always work out.
I spent last week at ICFP 2025. A nice (if exhausting!) week, as ever. Amusingly, the most reflections were actually sparked by Yaron’s talk which was right at the end (you can see the talk itself on YouTube).
Continuing the previous foray into file descriptors, and trying to remove Obj.magic both from ocaml-uring’s code itself, and from the recommended way for using it.
There was a flurry of activity on ocaml-multicore/ocaml-uring this month leading to a release (ocaml/opam-repository#28604). ocaml-uring provides bindings to the Linux’s io_uring, which allows batching various syscalls to the kernel for it to execute out-of-order, and in parallel. Its principal use at the moment is for the high-performance Linux backend of Eio.
Continuing the previous theme of dabbling with matters agentic. Previously, I’d quite assiduously kept my fingers away from files. This time, I wanted to try something exploratory, switching to the agent for things I was actively stuck on.
Over the summer, Lucas Ma has been investigating ideas surrounding using effects in the OCaml compiler itself. He’s blogged some of his discoveries and adventures. The technical core of this work leads towards being able to use the OCaml compiler as a library on-demand to create a longer-lived “compiler service”. Of itself, that’s not at all revolutionary, but it is quite hard to do that with a 30…