Thanks a lot for the MR. I don't have a windows machine to test this on so I can't reproduce locally. Nevertheless, I'll be reviewing this MR soon.

i dunno if you can get CI to run on the first diff (1d199cd) but it'll show the bug. for example: https://github.com/mroch/lwt/actions/runs/3284275234/jobs/5410034604

I believe the EINVAL comes from passing just a single null terminated string, without the additional \0 to terminate the block (and it's only passing the first of many envs, but I think it's the malformed block that causes the EINVAL specifically)

i dunno if you can get CI to run on the first diff

I don't know either. I don't understand github's UI very well. ❓ ❗

But that's ok. When I do the review I might push a branch with just the first commit to force the CI.

At first I was pleased that the code was so similar.
Then I thought it'd be even better if the code was even more similar.
And then I started thinking about licenses and now I don't know what to do about this PR.

I'll ask if it's ok. Basically, the added code is calling the functions provided by the ocaml project in the appropriate sequence. I think the alternative to using the same code is making a pull-request on the ocaml project to provide this sequence of calls as a function itself to be called. That might not be desirable upstream anyway…

Anyway, I'll ask.

A similar situation happened on the eio bugtracker:
ocaml-multicore/eio#352 (comment)

It's not exactly the same (not the same code being copied, not the same size of code) but it's also copying parts of the C code.

I've made raphael-proust/ocaml@bdbddd2 which aims to expose the code that we actually need from the OCaml source. Please leave comments on there, I don't know that I did anything correctly.

As per ocaml/ocaml#12492 (comment) it turns out licensing is not an issue. We can go ahead on this PR.