Cannot use unicode identifiers in `--extern` flags

[Nemo157]

I tried this code:

> rustc --crate-name öwö --crate-type lib - <<<'pub fn öwö() {}'
> rustc --crate-name ūwū --crate-type bin --extern öwö=liböwö.rlib - <<<'fn main() { öwö::öwö(); }'

I expected to see this happen: successful compilation

Instead, this happened:

error: crate name `öwö` passed to `--extern` is not a valid ASCII identifier

Meta

rustc --version --verbose:

rustc 1.85.0 (c44b3d50f 2024-12-03)
binary: rustc
commit-hash: c44b3d50fea96a3e0417e8264c16ea21a0a3fca2
commit-date: 2024-12-03
host: x86_64-unknown-linux-gnu
release: 1.85.0
LLVM version: 19.1.4

[bjorn3]

Rustc enforces ascii crate names in the metadata loader, not just for --extern:

rust/compiler/rustc_metadata/src/creader.rs

Lines 559 to 561 in 3da8bfb

	if !name.as_str().is_ascii() {
	return Err(CrateError::NonAsciiName(name));
	}

[Nemo157]

I assume that applies if you try using extern crate öwö;? I didn't actually try that in my original usecase because even after switching to edition = "2015" I was still getting the --extern error when building through cargo so it didn't seem like it would help.

The workaround I found for within a cargo project is to just rename the identifier passed on the cli and then rename it back within the crate:

ennead-protocol.package = "ἐννεάς-protocol"

extern crate ennead_protocol as ἐννεάς_protocol;

This does leave a vestigial ::ennead_protocol that it would be nice to avoid if it were natively supported.

[ehuss]

This was intentional when non-ascii idents were added to avoid dealing with filesystem differences and normalization issues.

[Nemo157]

The identifier on the left of the --extern flag doesn't affect the filesystem (when there's a path given too), using the workaround of renaming the dependency as I've shown uses unicode on the filesystem but not in the rustc interface.

[ehuss]

Yea, I see what you're asking now. Offhand I can't think of a particular restriction that might cause a problem with renaming on the command-line, especially if it already works via extern crate.