rust-lang / rust · Issue No. 163032

`Dir::open_file_with` (and likely more `Dir` methods) on Windows does not support `/`

Openby RalfJungopened Sep 19, 2026updated Sep 22, 20260 comments

O-windowsT-libsneeds-triage

Description

Usually, our fs methods on Windows support the / file separator, not just \. However, for the Dir methods, that does not seem to be true -- the following fails

dir.open_file_with("subdir/bar.txt", &OpenOptions::new().create(true).write(true))

saying

The filename, directory name, or volume label syntax is incorrect. (os error 123)

I suspect this is caused by internally using NtCreateFile rather than CreateFileW.

Tracking issue: https://github.com/rust-lang/rust/issues/120426
Cc @ChrisDenton @Qelxiros

Relay Analysis

View on GitHub

Relay reads this issue against the repository's contribution signals: the files it is likely to touch, how the maintainers triage work this size, and what the first contribution would exercise.

The full analysis for this issue is still being assembled. Until then, the description above and the thread on GitHub are the most reliable context.