std::os::windows::fs::symlink_file appears to incorrectly handle absolute paths

[valarauca]

I tried this code:

fn main() {
    let args = std::env::args().collect::<Vec<String>>();
    match std::os::windows::fs::symlink_file(&args[1], &args[2]) {
        Ok(()) => { },
        Err(e) => panic!("{:?}", e),
    };
}

I expected to see this happen:

When ran locally, it works fine.

.\simple_symlink.exe img.jpeg img2.jpeg

When ran with absolute paths

.\simple_symlink.exe 'E:\storage\videos\blobs\6B\7F\70\DB\Top Gun + Maverick (2022).mp4' 'E:\stroage\videos\actors\Tom Cruise\Top Gun + Maverick (2022).mp4'

thread 'main' panicked at src\main.rs:5:19:
Os { code: 87, kind: InvalidInput, message: "The parameter is incorrect." }

To be clear, the path does exist.

Instead, this happened: explanation

I expect a symlink is created.

I say this because, I am in developer mode.

I have granted myself the ability to create symlinks via secpol.msc as well.

So I don't believe it is a permission issue.

Meta

rustc --version --verbose:

rustc 1.85.0 (4d91de4e4 2025-02-17)
binary: rustc
commit-hash: 4d91de4e48198da2e33413efdcd9cd2cc0c46688
commit-date: 2025-02-17
host: x86_64-pc-windows-msvc
release: 1.85.0
LLVM version: 19.1.7

Windows 11 Pro for Workstations (AMD64)

[valarauca]

As the path in actually was longer than 260 characters, the sample used as simplified.

[bjorn3]

'E:\stroage\videos\actors\Tom Cruise\Top Gun + Maverick (2022).mp4'

You got a typo there I think. (storage vs stroage)

[ChrisDenton]

symlink_file is a fairly thin wrapper around CreateSymbolicLinkW. For absolute paths greater than MAX_PATH you'll currently need to use std::fs::canoncalize to get a path starting with \\?\.

The standard library could definitely be smarter here and do that automatically for you. Though care needs to be taken not to do this for relative paths as those might be intentionally relative (e.g. so a directory can be moved around without breaking the symlinks it contains).

[valarauca]

You got a typo there I think. (storage vs stroage)

Yeah this was a quick substitution as the real path was much longer and somewhat NSFW.

The standard library could definitely be smarter here and do that automatically for you.

It does?

• std::os::windows::symlink_file
• sys::fs::windows::symlink
• sys::fs::windows::symlink_inner
• sys::fs::windows::maybe_verbatim
• sys::fs::windows::get_long_path

The problem AFAIT is that a Manifest isn't embedded within the binary to actually enable long path functionality?

[ChrisDenton]

It does?

No it only does it for the path to the symlink, not the link's target

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

Line 1355 in a7fc463

let original = to_u16s(original)?;

This would need some additional logic to pass through simple relative paths but to make verbatim absolute paths longer than MAX_PATH.

[valarauca]

Cool.

Forcing long paths everywhere via the registery & embedding a manifest appears to have fixed my issue. I"ll close this as "Error exists between keyboard & chair".