Added implementation on `set_permissions_nofollow` for all primary platforms by asder8215 · Pull Request #158168 · rust-lang/rust

asder8215 · 2026-06-20T06:51:38Z

For context, this PR is related to the tracking issue for std::fs::set_permissions_nofollow. This PR does a few different things:

Windows support is provided for std::fs::set_permissions_nofollow. On Windows, it uses OpenOptions::open with the custom flag FILE_FLAG_OPEN_REPARSE_POINT enabled and then sets the permissions on the reparse point directly. All other platforms (hermit, motor, solid, uefi, etc.) defer to what fs::set_permissions does since symlinks aren't supported on those platforms, so they effectively do the same thing.
The implementation for Unix was modified to use fchmodat instead of doing two separate calls (open and then fchmod via OpenOptions).
Because the previous implementations actually used fchmod instead of chmod underneath the hood (as that's what File::set_permissions, which is not to be confused with fs::set_permissions as that does use chmod, does underneath the hood), it actually had some incorrect documentation about the error returned by fchmod on symlinks. Instead of io::ErrorKind::FilesystemLoop, it returns io::ErrorKind::InvalidInput. You can read the documentation for fchmod. fchmodat does effectively the same thing as the open + fchmod combo, but it does return a different error, io::ErrorKind::Unsupported, that makes more sense. Regardless, I corrected the documentation for std::fs::set_permissions_nofollow and added a lot more clarifying information.
A test case has been added to verify if set_permissions_nofollow is operating correctly.

cc @ChrisDenton and @lolbinarycat

rustbot · 2026-06-20T06:51:42Z

r? @clarfonthey

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Owners of files modified in this PR: @ChrisDenton, libs
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clarfonthey · 2026-06-20T12:09:10Z

 }

+pub fn set_perm_nofollow(path: &Path, perm: FilePermissions) -> io::Result<()> {
+    set_perm(path, perm)


Similar to UEFI, I would swap the method bodies here, so that set_perm defers to set_perm_nofollow plus a comment that says symlinks aren't supported.

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clarfonthey · 2026-06-20T12:15:58Z

@rustbot author

CI failure appears to be a simple typo but I also left some feedback on other stuff to fix. Otherwise, implementation looks good, although I would add an extra comment on the tracking issue once this is merged to have some Windows folks double-check that opening all reparse points in this method doesn't do anything we don't want, since that technically includes more than just symlinks. It should work in pretty much all normal use cases, just want to double-check the edge cases before stabilisation.

rustbot · 2026-06-20T12:16:02Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

…=<try> Added implementation on `set_permissions_nofollow` for all primary platforms try-job: dist-android

rust-bors · 2026-07-26T00:36:35Z

☀️ Try build successful (CI)
Build commit: 14aaf09 (14aaf09405c307a57e390837d3de751d64cb244e)
Base parent: 008fa22 (008fa22ce3f8d3c8dfaca2e6486043c2b21851eb)

clarfonthey · 2026-07-26T01:22:57Z

@bors r+ rollup=iffy Multitarget code that has failed us before, but hopefully shouldn't this time…

rust-bors · 2026-07-26T01:23:00Z

📌 Commit e14e3e9 has been approved by clarfonthey

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 100. This pull request will be tested once the tree is reopened.

Reason for tree closure: spurious failures

JonathanBrouwer · 2026-07-26T10:01:17Z

💔 I suspect this PR failed tests as part of a rollup
@bors r-

After fixing the problem, consider running a try job for the failed job before re-approving.

Link to failure: #159952 (comment)

rust-bors · 2026-07-26T10:01:25Z

This pull request was unapproved.

This PR was contained in a rollup (#159952), which was unapproved.

View changes since this unapproval

ChrisDenton · 2026-07-26T11:36:10Z

On Windows you can set attributes on symlinks (they're just normal files or directories).

View changes since the review

Got you. Does setting an attribute on symlinks do anything meaningful? I was reading up on MacOS and they also can set permission bits on symlinks, but they don't do anything meaningful.

Yes, it can be meaningful but only to the extent that setting the readonly attribute is meaningful. See Permissions::set_readonly, which notes that the readonly attribute on a directory is pretty useless nowadays. Tbh the name "Permissions" is a bit of misnomer on Windows as it doesn't set actual permissions.

asder8215 · 2026-07-26T16:06:19Z

@bors try jobs=x86_64-msvc-1

rust-bors · 2026-07-26T18:12:26Z

💔 Test for 4e6ca17 failed: CI. Failed job:

try - x86_64-msvc-1 (web logs, enhanced plaintext logs)

asder8215 · 2026-07-26T18:15:34Z

Okay, that confirms to me that Windows actually sets permissions on the symlink_dir(the BSD-based platforms we asserted false on readonly()).

…pported (windows, unix, uefi, etc.); modified the Unix implementation to use fchmodat instead of open + fchmod; clarified documentations for set_permissions_nofollow; added a test case for set_permissions_nofollow

asder8215 · 2026-07-26T18:34:59Z

@bors try jobs=x86_64-msvc-1

rust-bors · 2026-07-26T21:20:07Z

☀️ Try build successful (CI)
Build commit: a576dd2 (a576dd22a8ee6d6110ba0a6f8b58abff202994d0)
Base parent: 9451e06 (9451e069c34e1d7db23a155dcf9c25d1bc127055)

clarfonthey · 2026-07-28T20:13:04Z

Just to double-check: I think this is ready to merge again? And should work?

asder8215 · 2026-07-28T20:44:31Z

Just to double-check: I think this is ready to merge again? And should work?

All I can say is hopefully it works. It succeeded on x86_64-msvc-1, which implies to me that it succeeded on a Windows platform. However, I'm unsure if the other platforms will fail the tests or not. I apologize for any inconvenience on that end.

clarfonthey · 2026-07-28T20:57:42Z

Don't worry; this has been quite a surprising journey and I appreciate you continuing to travel down this path of madness. I'm content with just trying again, honestly.

@bors try rollup=iffy Fifth(?) time's a charm? Multi-platform code that continues to find platforms that misbehave.

rust-bors · 2026-07-28T20:57:45Z

Unknown argument "rollup". Did you mean to use @bors jobs=<jobs>|parent=<parent>? Run @bors help or go to https://bors.rust-lang.org/help to see available commands.

clarfonthey · 2026-07-28T20:58:08Z

🤦🏻

@bors r+ rollup=iffy Fifth(?) time's a charm? Multi-platform code that continues to find platforms that misbehave.

rust-bors · 2026-07-28T20:58:10Z

📌 Commit b319483 has been approved by clarfonthey

It is now in the queue for this repository.

RalfJung · 2026-07-29T16:19:18Z

+///     let mut perms = fs::symlink_metadata("foo.txt")?.permissions();
+///     perms.set_readonly(true);
+///     // This should result in an error on certain platforms
+///     // or succeed in modifying the permissions of a symlink


Or it might do nothing at all apparently, according to the comment above?

Yea, I forgot to update this once I noticed that it could do nothing at all

RalfJung · 2026-07-29T16:20:39Z

+/// if the final element is a symlink. On BSD-based systems, the
+/// behavior can vary from symlink permission bits changing or
+/// there being no effects on symlinks
+///


Suggested change

/// if the final element is a symlink. On BSD-based systems, the

/// behavior can vary from symlink permission bits changing or

/// there being no effects on symlinks

///

/// if the final element is a symlink. On BSD-based systems, the

/// behavior in this case can vary: the operation may have no effect at all

/// or it may change the permission bits of the symlink itself.

///

"can vary from... or ..." is not grammatical.

Note: this has already been merged, so, any suggestions would have to be under a separate PR. Could raise this in the tracking issue though.

I know...
@asder8215 any chance you could make a follow-up PR for doc clarifications and grammar fixes?

(apologies for missing this, by the way; after enough CI failures I was just incredibly happy this merged successfully)

Yeah I get it, it's hard to be on the look for docs nuances after fighting with the actual code for a while.

rustbot assigned clarfonthey Jun 20, 2026

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Missing variables/fields give confusing error when name is the same as a built-in attribute like start or path #86290

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rust-bors Bot pushed a commit that referenced this pull request Jul 26, 2026

Auto merge of #158168 - asder8215:windows_set_permissions_nofollow, r…

14aaf09

…=<try> Added implementation on `set_permissions_nofollow` for all primary platforms try-job: dist-android

rust-bors Bot 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 26, 2026

JonathanBrouwer mentioned this pull request Jul 26, 2026

Rollup of 25 pull requests #159952

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Implemented different with_native_path conversion methods, refactoring fs functions to utilize with_native_path, and move exists to use with_native_path #159805

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jhpratt mentioned this pull request Jul 29, 2026

Rollup of 11 pull requests #160112

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RalfJung mentioned this pull request Jul 29, 2026

Tracking Issue for std::fs::set_permissions_nofollow #141607

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