Add possibility to exclude binaries from being built on specific platforms

[philippkeller]

I have src/bin/linux-only.rs which does some things which work on Linux only (e.g. libc bindings which only exist on Linux). I want to exclude that file from being built on OS X.

Could you add a way to exclude those, e.g.

[package(target_os=macos)]
exclude = ["src/bin/linux-only.rs"]

or (and that's probably the better way as it doesn't need new syntax): just remove the error error: main function not found when there's a #![cfg(target_os = "linux")] at the top of src/bin/linux-only.rs

Disclaimer: I'm fairly new to rust so maybe I'm doing something wrong. I read through the Cargo.toml docs and didn't find a way to make this work, I also did not get a satisfying answer on this SO post.

[alexcrichton]

Thanks for the report! Yeah in Cargo right now this isn't too easy, but you can work around this with #[cfg] where on the non-relevant platforms it's just an empty fn main() {} with maybe a println! diagnostic explaining why.

[philippkeller]

@alexcrichton that's what I'm currently doing. But it needs a #[cfg] attribute above every block (including use, structs, c bindings, etc. So I end up with 10-20 of these attributes which is cluttering the code. Is there a better way to do that?

[philippkeller]

found a workoround via a build.sh script that generates separate Cargo.toml files for linux and osx, which leaves out rs files with the #![cfg(target_os = "...")] which doesn't match the current architecture.

[weihanglo]

Hey there. I am going to close this since more discussions happens in #9208 for the same issue. Thank you!