Add more WASI libc bindings

[sunfishcode]

I was writing some WASI code and needed some more bits from libc. Here's a patch adding more things from the intersection of things that WASI libc defines and things that other platforms in libc have bindings for.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @gnzlbg (or someone else) soon.

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[gnzlbg]

@alexcrichton this LGTM, wasi is experimental so I don't see any issues with iterating on this in tree.

Some of the symbols are named __wasilibc, but others aren't. Is there a reason for this?

[sunfishcode]

Some of the symbols are named __wasilibc, but others aren't. Is there a reason for this?

The __wasilibc_* functions are functions which are WASI-specific and not part of a typical libc API.

[alexcrichton]

All looks good to me!

@sunfishcode looks like there's some verification errors on CI, and libc-test/build.rs may need to be updated for including more headers files or such on wasi.

While you're here, want to update the wasi check in src/lib.rs to any(target_env = "wasi", target_os = "wasi")?

[alexcrichton]

@bors: r+

[bors]

📌 Commit 5fda33e has been approved by alexcrichton

[bors]

⌛ Testing commit 5fda33e with merge 19e81f3...

[sunfishcode]

Investigating this more, this has turned up some bugs in on the wasi-sysroot side, so I'm going to step back here momentarily, fix those, and them come back to this.