add HermitOS support to branch v0.8.x

[stlankes]

Backport of #1759

HermitOS is a library operating system. The handling of the socket streams is compatible to unix. However, other parts are not compatible to Unix. Consequently, HermitOS doesn't belong to the unix family.

To support MIO, MIO's unix is revised to support HermitOS. Currently, the implementation based on the unix system poll.

[stlankes]

Hm, I think that the my changes aren't the reason for the clippy warnings

[Thomasdezeeuw]

Hm, I think that the my changes aren't the reason for the clippy warnings

You can ignore the Clippy warnings.

[Thomasdezeeuw]

So, we're using hermit-abi as libc? That's rather misleading.

[Thomasdezeeuw]

I just realised I accept it on master, that was a mistake.

[stlankes]

I can rename it to hermit_abi. Should we also rename src/sys/unix to src/sys/hermit because the prefix libc is often used in this directory. But the code is more or less identical. Also in other parts of the prefix is often used and code is identical.

[stlankes]

Ah, I have an idea to solve it. I will revise it.

[Thomasdezeeuw]

Can you add this to the CI and the Makefile as well?

[stlankes]

Yes, I will do it.

[Thomasdezeeuw]

I just realised I accept it on master, that was a mistake.

[Thomasdezeeuw]

I made some changes to the cfg of Hermit in #1789, this should be reflected when backporting to v0.8.

[stlankes]

Looks good for me. By the way, we try to move parts of ABI to libc (see rust-lang/libc#3724). At least the stabilized interfaced should be moved to libc.

[stlankes]

I have to revert a8a5c5b We don't return always -1. It could be also other negative values.

I wait also for rust-lang/libc#3766 to be part of libc 0.2.

[Thomasdezeeuw]

I have to revert a8a5c5b We don't return always -1. It could be also other negative values.

Should we also fix that in v1:

mio/src/sys/unix/mod.rs

Lines 5 to 15 in 1ce1545

	macro_rules! syscall {
	($fn: ident ( $($arg: expr),* $(,)* ) ) => {{
	#[allow(unused_unsafe)]
	let res = unsafe { libc::$fn($($arg, )*) };
	if res < 0 {
	Err(std::io::Error::last_os_error())
	} else {
	Ok(res)
	}
	}};
	}

?

I wait also for rust-lang/libc#3766 to be part of libc 0.2.

👍 also like to make this change in v1.

Is the main aim of this to support Tokio? Because if so, it might make more sense to merge tokio-rs/tokio#6635 instead.

[stlankes]

Should we also fix that in v1:

The code in v1 is correct and similar to the current version in 0.8.

Is the main aim of this to support Tokio? Because if so, it might make more sense to merge tokio-rs/tokio#6635 instead.

Yes! What is the current state of tokio-rs/tokio#6635 ?

[Darksonn]

The summary I gave in tokio-rs/tokio#6635 (comment) is still accurate. I am on vacation right now.

[Thomasdezeeuw]

I am on vacation right now.

Then you should not be reading emails/GitHub, but enjoying your vacation instead ;)

[stlankes]

I think, we can close this PR. mio 1.0 is already used by tokio