BenjaminRi
commented
1 year ago Unfortunately, this doesn't work. The crate can be used in cross-compile scenarios, so what matters is the target operating system. However, even #[cfg(windows)] or #[cfg(target_os = "windows")] is not the proper condition attribute, as a build for Windows, compiled on Linux, will compile build.rs with target operating system Linux, hence not compiling the Windows part. This is also explained in the Readme. The examples in the Readme and the implementation of this detail are actually very carefully chosen to work around all these annoying corner cases. I know it's not perfect, and it sometimes compiles too much, but it's the best that can be done to work in a broad set of circumstances. Unfortunately, in cross-compilation scenarios, there is no way to use conditional compilation for the actual target we are compiling the library for when building build.rs, that is the root cause of the issue.
Indeed, the extern crate statement seems superfluous now. That change makes sense and I would merge that.
rhysd
This PR improves usage document in README.md.
#[cfg(windows)]attribute is compiled only on Windows. This speeds up compilation of build.rs.extern crateis no longer necessary after Rust 2018. When runningcargo new, the default edition is Rust 2021.