Add an unstable option to build proc macros for both the host and the target #6547
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Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @alexcrichton (or someone else) soon. If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes. Please see the contribution instructions for more information. |
Zoxc
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Sorry, can you help me understand when this would be needed? |
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This is needed when you want to cross compile a library for a target A which uses a proc macro crate. Currently we'll only compile the proc macro crate for the host, which means the proc macro crate won't be usable if we actually run the compiler on target A and we try to use our cross compiled library. Note that our library can reexport the macros from the proc macro crate, so it needs to be available to run on the target. |
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So I think I am still not understanding. You are cross compiling a rust library (not a final artifact) so that the target can use that file as part of a rust build? There is no rust abi. I am surprised that it works at all. The workflow I would have expected are to:
But I do not know much about the uses of cross compiles, can you explain why you are doing this workflow? |
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@Eh2406 I think a missing piece of information is that this is for the compiler itself. The compiler gets a free pass with unstable features because it deals with its own breakage, and I suspect that this feature would be unlikely to ever graduate from unstable status. @Zoxc I think before merging this it'd be good to get a working build first. This may not be all that's needed on Cargo's end, so could this be used with a local build of Cargo to test out support in rustc? |
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@alexcrichton I should be able to test these change locally, but I was hoping to sneak this into the upcoming release since I can't actually land changes in rustc until this is in beta. |
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We can backport this for rustc to unblock work there, so I'm not too worried about the scheduling here |
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☔ The latest upstream changes (presumably #6573) made this pull request unmergeable. Please resolve the merge conflicts. |
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@Zoxc is this ready to go for rust-lang/rust#58013? If so I think this is fine to land on this branch and beta to get it in for the compiler |
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This should be good to go |
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Friendly ping, branching is going to happen soon. |
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I'm working on a research project where I need to use serde in the compiler. It'd be neat if this could be merged soon, so that #58013 can be unblocked. Thanks :) |
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@bors: r+ |
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📌 Commit 2a95bd0 has been approved by |
Add an unstable option to build proc macros for both the host and the target r? @alexcrichton
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☀️ Test successful - checks-travis, status-appveyor |
Update cargo 9 commits in 865cb70106a6b1171a500ff68f93ab52eea56e72..b33ce7fc9092962b0657b4c25354984b5e5c47e4 2019-02-10 15:49:37 +0000 to 2019-02-19 18:42:50 +0000 - Don't retry invalid credentials from git credential helpers (rust-lang/cargo#6681) - Fix some typos in resolver tests (rust-lang/cargo#6682) - Add an unstable option to build proc macros for both the host and the target (rust-lang/cargo#6547) - Test cases proving RUSTC_WRAPPER can be a relative path (rust-lang/cargo#6638) - Add support for Azure DevOps (rust-lang/cargo#6264) - Update docs for removed `patch` restriction. (rust-lang/cargo#6663) - Fix incorrect help message (rust-lang/cargo#6555) - Stabilize Alternative Registries (rust-lang/cargo#6654) - Having a [patch] section when publishing is not an error (rust-lang/cargo#6535)
r? @alexcrichton