chore: update unix primitives names for 5.2

[kopecs]

ocaml/10926 updates the runtime functions from Unix in 5.x to be prefixed with caml_, which they previously were not. Thus we need to update that here.

[github-actions]

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[kopecs]

cc: @brandonspark if you're working on this

[aryx]

Does that mean the code will not compile with OCaml 4.14.0?
or using caml_xxx is backward compatible?

[kopecs]

Does that mean the code will not compile with OCaml 4.14.0?

That's correct -- they made a breaking change to the names. This should only get merged if we are building with 5.x.

[aryx]

That's annoying, because it's nice to be able to both compile in CI for 4.14.1 and 5.2.0.
Maybe we could use some ifdefs in this code? to make the code portable on both OCaml version?
I usually hate ifdefs, but might be a good use case here.

[ajbt200128]

@kopecs I don't see any reason why we can't export the function under both names. Ugly, and clutters the global namespace a bit, but shouldn't break anything. Might even be able to do //provides: name1, name2 or something simple

[kopecs]

Oh, perhaps. Not particularly opposed, but I would figure it just makes more sense to swap over when we move to 5 given we'd presumably be using other features which aren't backwards compatible so it wouldn't matter if this built with 4.

[ajbt200128]

I think @aryx wants to be able to have 5.2 working in CI before we actually start using its features and/or releasing with it. So we probably want to be able to merge this and have both versions work for now

[aryx]

yep, @ajbt200128 is correct;