How to cache/shorten cross-compilation of windows builds?

[mpizenberg]

I'm currently cross-compiling for Windows with maturin build --release --target x86_64-pc-windows-msvc --zig and adding the generate-import-lib feature to pyo3. This combination makes my GitLab builds timings increase by roughly 10 minutes. What is the main culprit for that? And is it possible to cache whatever happens during these 10 minutes? For now I'm caching .cargo/ and target/ but it does not seem to make a difference.

This question might be related to #1947

[messense]

You can try to cache ~/.cache/cargo-xwin.

[messense]

XWIN_CACHE_DIR probably won't work in maturin because it was a clap env option in cargo-xwin, the way we call cargo-xwin in maturin is a bit different which does not go through clap.

So I think we need to add support for it in

maturin/src/compile.rs

Lines 282 to 288 in b209c4b

	#[cfg(feature = "xwin")]
	{
	let mut build = cargo_xwin::Rustc::from(cargo_rustc);
	build.target = vec![target_triple.to_string()];
	build.build_command()?
	}

, pull requests are welcome.

[mpizenberg]

Ok, thanks for the pointer. I doubt I can tackle this in short term. Hopefully somebody will.

[NfNitLoop]

Thanks for the info! I'm doing a build inside of Docker and this will allow me to use a cache mount to speed things up dramatically on my slow internet. 😊

I can only cache paths within the repo in gitlab

@mpizenberg Maybe as a workaround your GitLab build can just add a symlink from ~/.cache/cargo-xwin into a directory in your repo?

[messense]

Maybe you can try set XDG_CACHE_HOME env var to a path in the repo since cargo-xwin uses dirs crate which follows the XDG base directory spec.

[mpizenberg]

Thanks @NfNitLoop and @messense for the ideas. I haven't tested the symlink idea, but I can confirm that setting XDG_CACHE_HOME to $CI_PROJECT_DIR/.cache and caching .cache/ works in GitLab :)

[messense]

I'm adding support for cargo-xwin env vars in #1961 to make things easier.