Cross-compilation linux -> windows

[stuvet]

Hi,

Thanks for the work you've put into this. Very helpful.

So I've been having 'fun' with Linux -> Windows cross-compilation over the last few days. I'd initially seen the x86_64-pc-windows-msvc & i686-pc-windows-msvc on docs.rs and thought life would be good. After having some problems with compilation as a dependency I noticed the call for Windows PRs, so maybe I was accidentally misinformed by docs.rs? I certainly had some issues with my toolchain, so perhaps all the problems were at my end.

But for what it's worth:

Problem

In isolation librclone compiles on linux without error for targets x86_64-pc-windows-msvc & x86_64-pc-windows-gnu. Once try to reference any of its functions things start going very wrong, as it can't find librclone.a even though it's been produced - presumably compiled for the host architecture, according to an inserted go env at the same place of the librclone-sys/build.rs.

Solution

I think I've worked around all my issues, and now seem to be able to reference its functions as a dependency in cross-compiled x86_64-pc-windows-gnu & i686-pc-windows-gnu targets (though not -msvc so far).

I can do this with fb680cc by passing suitable GOOS, GOARCH, CC, CGO_ENABLED, CGO_CFLAGS & CGO_LDFLAGS to cargo build, but changing (particularly) CC may have other unwanted effects for other users.

I still need to do some testing though...

Proposal

Would you be interested in a PR which tries to autodetect some of these & inserts them as environment variables in the go build call? To warn you, there would likely need to be some good documentation on setting up the required environment too, & perhaps the inevitable mountain of 'issues' means this isn't something you'd like to support on here!

I guess a simpler alternative would be to leave the code as-is and offer some documentation for cross-compilation to windows.

Thoughts?

[trevyn]

There's currently no intentional support for Windows, cross-compilation or otherwise.

My primary concern regarding Windows is to have something that's testable in CI with a GitHub Actions Windows runner.

I'm hesitant to add too much that's specific to cross-compilation unless upstreaming it would be useful to you and it's fairly straightforward.

Anything that you could add for building on Windows, for Windows, would be appreciated.