Avoid zeroing a 1kb stack buffer on every call to std::sys::windows::fill_utf16_buf

[thomcc]

I've also tried to be slightly more careful about integer overflows, although in practice this is likely still not handled ideally.

r? @ChrisDenton

[rustbot]

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

• Stabilizing library features
• Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
• Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
• Changing public documentation in ways that create new stability guarantees
• Changing observable runtime behavior of library APIs

[thomcc]

FYI: I wrote this on macOS, so probably don't r+ this without a try run first (it should be fine but for all I know I got some logic backwards or something).

[ChrisDenton]

Well it doesn't look like there's anything in the try queue atm so we might as well use it for something...

@bors try

[bors]

⌛ Trying commit f50f878 with merge d286d96ed7aad502865c5797ecb8c6c49237bb5f...

[Mark-Simulacrum]

Try builds are Linux only dist builds without extra work so it probably won't show anything interesting.

[thomcc]

Try builds are Linux only dist builds without extra work so it probably won't show anything interesting.

Nards. I was pretty sure I'd seen them run the windows CI tests before.

[ChrisDenton]

Oh! That's annoying. If it helps I can test locally when I have a mo.

[Mark-Simulacrum]

https://github.com/rust-lang/rust/blob/master/.github/workflows/ci.yml#L7 has the file you need to edit and rerun the expander to regenerate the actual configuration. Mostly just a matter of copying a windows job to the try: section.

[klensy]

There few similar places like that

rust/library/std/src/sys/windows/stdio.rs

Line 60 in 8064a49

const MAX_BUFFER_SIZE: usize = 8192;

rust/library/std/src/sys/windows/stdio.rs

Lines 171 to 173 in 8064a49

	fn write_valid_utf8_to_console(handle: c::HANDLE, utf8: &str) -> io::Result<usize> {
	let mut utf16 = [0u16; MAX_BUFFER_SIZE / 2];
	let mut len_utf16 = 0;

or

rust/library/std/src/sys/windows/c.rs

Line 158 in 8064a49

pub const MAXIMUM_REPARSE_DATA_BUFFER_SIZE: usize = 16 * 1024;

rust/library/std/src/sys/windows/fs.rs

Lines 328 to 330 in 8064a49

	if info.dwFileAttributes & c::FILE_ATTRIBUTE_REPARSE_POINT != 0 {
	let mut b = [0; c::MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
	if let Ok((_, buf)) = self.reparse_point(&mut b) {

[bors]

☀️ Try build successful - checks-actions
Build commit: d286d96ed7aad502865c5797ecb8c6c49237bb5f (d286d96ed7aad502865c5797ecb8c6c49237bb5f)

[ChrisDenton]

Ok I've tested this locally and it looks great so let's get this merged.

@bors r+ rollup

[bors]

📌 Commit f50f878 has been approved by ChrisDenton

It is now in the queue for this repository.

[ChrisDenton]

@bors r- update comments

[ChrisDenton]

@bors r+ rollup

[bors]

📌 Commit d4cba61 has been approved by ChrisDenton

It is now in the queue for this repository.