Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag #101260

ChrisDenton · 2022-09-01T03:30:43Z

I've been looking at this code recently and it just occurred to me we don't actually use the full reparse data at this point, only the tag. GetFileInformationByHandleEx can do exactly that by filling a FILE_ATTRIBUTE_TAG_INFO struct.

r? @thomcc since you've made changes here recently (which is why I have this code on my mind atm)

This avoid unnecessarily getting the full reparse data when all we need is the tag.

thomcc

Ah, great!

thomcc · 2022-09-01T23:17:45Z

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

+                    self.handle.as_raw_handle(),
+                    c::FileAttributeTagInfo,
+                    ptr::addr_of_mut!(attr_tag).cast(),
+                    mem::size_of::<c::FILE_ATTRIBUTE_TAG_INFO>().try_into().unwrap(),


Kind of goofy to do this here, but I guess I'm not opposed since the unwrap should vanish and I would generally like us to be more careful about a usize->dword.

Yeah. I was thinking of our conversation here and noticed it codegened fine. But it is weird. I do think it'd ultimately be better to have a proper wrapper for these cases that can statically assert the size fits into a u32. And also something for the cases that could possibly fail.

thomcc · 2022-09-01T23:18:03Z

@bors r+

bors · 2022-09-01T23:18:05Z

📌 Commit 630f831 has been approved by thomcc

It is now in the queue for this repository.

Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag I've been looking at this code recently and it just occurred to me we don't actually use the full reparse data at this point, only the tag. [`GetFileInformationByHandleEx`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getfileinformationbyhandleex) can do exactly that by filling a [`FILE_ATTRIBUTE_TAG_INFO`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/ns-winbase-file_attribute_tag_info) struct. r? `@thomcc` since you've made changes here recently (which is why I have this code on my mind atm)

Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag I've been looking at this code recently and it just occurred to me we don't actually use the full reparse data at this point, only the tag. [`GetFileInformationByHandleEx`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getfileinformationbyhandleex) can do exactly that by filling a [`FILE_ATTRIBUTE_TAG_INFO`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/ns-winbase-file_attribute_tag_info) struct. r? ``@thomcc`` since you've made changes here recently (which is why I have this code on my mind atm)

Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag I've been looking at this code recently and it just occurred to me we don't actually use the full reparse data at this point, only the tag. [`GetFileInformationByHandleEx`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getfileinformationbyhandleex) can do exactly that by filling a [`FILE_ATTRIBUTE_TAG_INFO`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/ns-winbase-file_attribute_tag_info) struct. r? ```@thomcc``` since you've made changes here recently (which is why I have this code on my mind atm)

Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag I've been looking at this code recently and it just occurred to me we don't actually use the full reparse data at this point, only the tag. [`GetFileInformationByHandleEx`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getfileinformationbyhandleex) can do exactly that by filling a [`FILE_ATTRIBUTE_TAG_INFO`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/ns-winbase-file_attribute_tag_info) struct. r? ````@thomcc```` since you've made changes here recently (which is why I have this code on my mind atm)

Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag I've been looking at this code recently and it just occurred to me we don't actually use the full reparse data at this point, only the tag. [`GetFileInformationByHandleEx`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getfileinformationbyhandleex) can do exactly that by filling a [`FILE_ATTRIBUTE_TAG_INFO`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/ns-winbase-file_attribute_tag_info) struct. r? `````@thomcc````` since you've made changes here recently (which is why I have this code on my mind atm)

Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag I've been looking at this code recently and it just occurred to me we don't actually use the full reparse data at this point, only the tag. [`GetFileInformationByHandleEx`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getfileinformationbyhandleex) can do exactly that by filling a [`FILE_ATTRIBUTE_TAG_INFO`](https://docs.microsoft.com/en-us/windows/win32/api/winbase/ns-winbase-file_attribute_tag_info) struct. r? ``````@thomcc`````` since you've made changes here recently (which is why I have this code on my mind atm)

…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#100121 (Try normalizing types without RevealAll in ParamEnv in MIR validation) - rust-lang#100200 (Change implementation of `-Z gcc-ld` and `lld-wrapper` again) - rust-lang#100814 ( Porting 'compiler/rustc_trait_selection' to translatable diagnostics - Part 1) - rust-lang#101215 (Also replace the version placeholder in rustc_attr) - rust-lang#101260 (Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag) - rust-lang#101323 (Remove unused .toggle-label CSS rule) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

RalfJung · 2022-09-02T21:26:31Z

Is it possible that this caused #101344 ?

ChrisDenton · 2022-09-03T01:48:38Z

I admit I'm struggling to see how it would be.

thomcc · 2022-09-03T04:39:19Z

Given that its an ICE which contains:

query stack during panic:
#0 [mir_drops_elaborated_and_const_checked] elaborating drops for `sys::windows::fs::<impl at D:\a\rust\rust\library\std\src\sys\windows\fs.rs:278:1: 278:10>::file_attr`
#1 [optimized_mir] optimizing MIR for `sys::windows::fs::<impl at D:\a\rust\rust\library\std\src\sys\windows\fs.rs:278:1: 278:10>::file_attr`
end of query stack

it seems like this did cause the issue, since compiling this code seems to have unearthed a latent compiler bug which results in this ICE.

Unless the code is actually wrong I don't think we want to back it out, but if it's impossible to fix in rustc and is a huge issue for miri I suppose we could tweak it or keep the old version behind #[cfg(miri)]. I'd rather not, tho.

ChrisDenton · 2022-09-03T06:00:25Z

For sure, I'm not at all saying this didn't trigger a bug. But, as far as I can tell (tho I may be mistaken), this isn't the root cause. And it feels a bit unsatisfactory to fix a symptom and not the root cause. Although I guess a temporary workaround is fine (so long as it is actually temporary).

Also, yeah, I'd really love to avoid #[cfg(miri)] as much as we can get away with.

RalfJung · 2022-09-03T07:14:36Z

I agree that this can't be the bug that causes the ICE, it just uncovers an existing bug, but also I have no way of even debugging the Miri fault (it only happens on Windows on CI), so until someone else figures that out Miri is stuck.

Use FILE_ATTRIBUTE_TAG_INFO to get reparse tag

630f831

This avoid unnecessarily getting the full reparse data when all we need is the tag.

rust-highfive assigned thomcc Sep 1, 2022

rustbot added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Sep 1, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 1, 2022

ChrisDenton added the O-windows Operating system: Windows label Sep 1, 2022

thomcc approved these changes Sep 1, 2022

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 1, 2022

Dylan-DPC mentioned this pull request Sep 2, 2022

Rollup of 9 pull requests #101314

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Dylan-DPC mentioned this pull request Sep 2, 2022

Rollup of 9 pull requests #101315

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Dylan-DPC mentioned this pull request Sep 2, 2022

Rollup of 8 pull requests #101317

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matthiaskrgr mentioned this pull request Sep 2, 2022

Rollup of 6 pull requests #101326

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This was referenced Sep 2, 2022

Rollup of 7 pull requests #101327

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Rollup of 6 pull requests #101328

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matthiaskrgr mentioned this pull request Sep 2, 2022

Rollup of 6 pull requests #101333

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bors merged commit 1e008fe into rust-lang:master Sep 2, 2022

rustbot added this to the 1.65.0 milestone Sep 2, 2022

ChrisDenton deleted the attribute-tag branch September 3, 2022 06:44

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Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag #101260

Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag #101260

ChrisDenton commented Sep 1, 2022

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thomcc commented Sep 1, 2022

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thomcc commented Sep 3, 2022

ChrisDenton commented Sep 3, 2022 •

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RalfJung commented Sep 3, 2022 via email

Use FILE_ATTRIBUTE_TAG_INFO to get reparse tag #101260

Use FILE_ATTRIBUTE_TAG_INFO to get reparse tag #101260

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RalfJung commented Sep 3, 2022 via email

Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag #101260

Use `FILE_ATTRIBUTE_TAG_INFO` to get reparse tag #101260

ChrisDenton commented Sep 3, 2022 •

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