3 The behavior of the `--extern` flag can be modified with `noprelude`, `priv` or `nounused` options.
5 This is unstable feature, so you have to provide `-Zunstable-options` to enable it.
9 Use your own build of the `core` crate.
11 `rustc main.rs -Z unstable-options --extern noprelude:core=libcore.rlib`
13 To use multiple options, separate them with a comma:
15 `rustc main.rs -Z unstable-options --extern noprelude,priv,nounused:mydep=mydep.rlib`
19 * `noprelude`: Do not add the crate to the external prelude. If used, it will need to be imported using `extern crate`.
20 This is used by the [build-std project](https://github.com/rust-lang/wg-cargo-std-aware/) to simulate compatibility with sysroot-only crates.
21 * `priv`: Mark the crate as a private dependency for the [`exported_private_dependencies`](../../rustc/lints/listing/warn-by-default.html#exported-private-dependencies) lint.
22 * `nounused`: Suppress [`unused-crate-dependencies`](../../rustc/lints/listing/allowed-by-default.html#unused-crate-dependencies) warnings for the crate.