Unexpected cfgs beginning with nightly-2024-11-20

[smoelius]

Beginning with nightly-2024-11-20 (today), compiling a simple program like this:

#[ctor::ctor]
fn init() {}

produces a warning like this:

warning: unexpected `cfg` condition value: `used_linker`
 --> src/lib.rs:1:1
  |
1 | #[ctor::ctor]
  | ^^^^^^^^^^^^^
  |
  = note: no expected values for `feature`
  = help: consider adding `used_linker` as a feature in `Cargo.toml`
  = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
  = note: `#[warn(unexpected_cfgs)]` on by default
  = note: this warning originates in the attribute macro `ctor::ctor` (in Nightly builds, run with -Z macro-backtrace for more info)

This appears to be the relevant rustc change: rust-lang/rust#132577

My best guess is that these lines are the cause:

rust-ctor/ctor/src/lib.rs

Lines 180 to 181 in fc9cd68

	#[cfg_attr(not(feature = "used_linker"), used)]
	#[cfg_attr(feature = "used_linker", used(linker))]

Adding used_linker as a feature to the project makes the warning go away, but I suspect this is not the intent.

[mmastrac]

Ack. This was certainly an oversight in the original implementation of this feature.

I'll ponder a fix for this. Thanks for the great report.

[mmastrac]

Fixed and released as 0.2.9.

[smoelius]

Thanks for the prompt fix!