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Pants

I'm general bumping your fd limit is a solid plan. You can also try running tests less in parallel with `cargo test -- --test-threads=1` if you end up bumping into resource limits you can't overcome

I wonder why I didn't run into this yesterday

does it repro if you jump back a few commits?

1024 is a small number in general though imho

yea, i think approximately everyone runs into this at some point on osx

looks like it's 592c511409b8d9970198cd313ede45b2b85e0ef6 that breaks on my system

Use Docker to build Python 3.7 PEX in CI (#7899)

I wonder if these are transient failures?

yea, you need to fix your FD limit. that's not new.

sorry. we could add something to warn if it's too low probably.

okay with the FD limit fixed I get, transliently

```---- tests::backoff_when_unhealthy stdout ----
thread 'tests::backoff_when_unhealthy' panicked at 'called `Result::unwrap()` on an `Err` value: Canceled', src/libcore/result.rs:997:5


```

that... might just be a flaky test. sigh.

can check the `flaky-test` label in github to see if it's been reported

<@UKQ8DL2PP>: re: traps crossing the cffi boundary. function pointers need to have the appropriate shape: <https://github.com/pantsbuild/pants/blob/55a562c772aea7693f0ae805487ad4e7998056c4/src/rust/engine/src/externs.rs#L23-L25> vs <https://github.com/pantsbuild/pants/blob/55a562c772aea7693f0ae805487ad4e7998056c4/src/python/pants/engine/native.py#L285-L291> , for example

_most_ other pitfalls were resolved via cbindgen though (yay, thanks Danny!)

there is still some boilerplate that could be made better

luckily that can just mean editing python and editing rust now

is it possible to have a C extern rust function with an Option&lt;&gt; parameter?

Yes: <https://github.com/eqrion/cbindgen/blob/master/docs.md#supported-types>

which would imply it doesn't work for rust types that aren't underlyingly pointers

Hrm. It would be strange if Option&lt;u64&gt; were'nt supported since, IIUC A None maps to the equivalent of NULL.

er, it's only for references, which can't be 0, so rustc can optimize

maybe a better question is,what's the idiomatic way to pass a value that may be `None` or may be something from python into a rust FFI function? (I think I'll need this for the union stuff I was talking about earlier)

cbindgen should tell you something useful if it isn't possible

things like `enums` work (with an interesting syntax), which surprised me

I didn't find an obvious way when I was passing `Option&lt;String&gt;` around, but empty strings weren't valid where I was so I just used empty as `None`. I suspect you may need to just pass around a bool and a value, unless cbindgen offers you something fancy

I think that if it generates that same syntax for all enums, then... It might just do that for `Option` as well...?