Rust build-support: enabling cross-compilation of Rust code #47976
Conversation
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Looks okay to me! I had this commit that might be helpful: Feel free to cherry-pick it if it's helpful. I don't have enough familiarity with rust to do much. |
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Done, thanks for the input! I started working on this a while ago, which is why I didn't get a chance to see your commit (nothing worked for an embarrassingly long time). |
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Wait, actually, your commit is about the cargo-based compilation system, which explains better why I hadn't seen it. This PR is about the other system (the Carnix-based one). The Carnix-based system uses Nix instead of Cargo to do the dependency management. This is really useful, since all the crates are independent derivations, and you don't need to recompile the world every time you change the final crate. As an example, I spent way less time working on Carnix in total than waiting for the server of https://nest.pijul.com to finish compiling. The only downside is that the Carnix-based system sometimes lags behind compared to Cargo, since the configuration files of Cargo might change, and no one is currently tracking these changes too closely. Also, this PR means that the Carnix-based system is now more advanced than the Cargo-based one (and I know it shouldn't make me happy). |
| rustPlatform = | ||
| with stdenv.hostPlatform.parsed; | ||
| let cpu_ = if cpu.name == "armv7a" then "armv7" | ||
| else cpu.name; |
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I'd rather have a fixed and known-to-work name mapping instead of such hardcoded special cases.
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Me too!
If you know of any such naming, great. Rustc doesn't seem to respect GNU conventions, NixOS does. I don't want to sound scary, but most, if not all, of rustBuildCrate was built by trial and error.
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Asking in #rustc they pointed me to https://github.com/rust-lang/rust/tree/master/src/librustc_target/spec where this stuff is apparently declared, soo if somebody feels inclined to do a mapping for them there you go :P
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They also said they match llvm targets, and those are defined in each file as well
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You can get list of supported targets and their names by running rustc --print target-list.
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Merged into #40587. |
Motivation for this change
The Rust build-support in Nixpkgs was lacking cross-compilation support, mostly because 'rustc' was not using the proper linker. Another issue is the difference in platform names (for instance ARMv7) between Gnu and Rust.
Things done
sandboxinnix.confon non-NixOS)nix-shell -p nox --run "nox-review wip"./result/bin/)nix path-info -Sbefore and after)