1 error[E0658]: the `linkage` attribute is experimental and not portable across platforms (see issue #29603)
2 --> $DIR/linkage4.rs:1:1
4 LL | #[linkage = "external"]
5 | ^^^^^^^^^^^^^^^^^^^^^^^
7 = help: add #![feature(linkage)] to the crate attributes to enable
9 error: aborting due to previous error
11 For more information about this error, try `rustc --explain E0658`.