Add wasi select, FD_SET, FD_ZERO, FD_ISSET

[youknowone]

Please check if it fits in the project policy.

This is port of wasi-libc type definitions and functions. wasi-libc has different fd_set design to widely used one.

[rustbot]

r? @JohnTitor

rustbot has assigned @JohnTitor.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[tgross35]

Could you start a wasi file at libc-test/semver and add these? Also needs a rebase.

I believe this is the original source: https://github.com/WebAssembly/wasi-libc/blob/230d4be6c54bec93181050f9e25c87150506bdd0/libc-bottom-half/headers/public/__fd_set.h and https://github.com/WebAssembly/wasi-libc/blob/230d4be6c54bec93181050f9e25c87150506bdd0/libc-bottom-half/headers/public/__typedef_fd_set.h#L10-L12

[tgross35]

@rustbot author

[youknowone]

@rustbot review

[tgross35]

Thanks!

This is fine as-is, but please consider adding FD_CLR and FD_COPY as a followup PR so we have all the functions in that file.

[tgross35]

@youknowone it looks like this isn't working when the rustc-dep-of-std feature is enabled (which is how std is allowed to have dependencies), see here rust-lang/rust#129226 (comment). Could you put up a fix for it? You should just need to update this line to include super::{Send, Sync, iter::Iterator}:

libc/src/wasi.rs

Line 4 in 5375260

use super::{Send, Sync};

Try the build locally, you may also need #[allow(unused_imports)] if Cargo complains