Cargo-sysroot

A (dumb) tool to compile the sysroot crates for your no_std application.

This is not a wrapper like cargo xbuild or xargo, this is a standalone tool you call once. This has the nice benefit of actually working with standard tools like RLS, clippy, or even the simple cargo check. It accomplishes this by generating a .cargo/config for you.

Prerequisite

• A nightly compiler.
• The rust-src component must be installed for the active toolchain.
• Your Cargo.toml file must contain package.metadata.cargo-sysroot.target, where target is a target specification json file.
  • A built-in target may also work, but this is untested.
• OR Pass --target on the command line, ex cargo sysroot --target path/to/target.json

Example Cargo.toml

```toml [package] name = "My Project" version = "0.1.0" authors = ["Me Me@Me.com"]

[package.metadata.cargo-sysroot] target = "mycustomtarget.json" # This is relative to Cargo.toml ```

Getting Started

• Run cargo install cargo-sysroot.
• Run cargo sysroot in the working directory of your project.

This tool will generate a .cargo/config for you that looks something like this. This can be disabled via the --no-config command-line option, but note that you will then have to tell cargo about your target and sysroot location some other way.

toml [build] target = "path/to/your/target/specification/json" rustflags = [ "--sysroot", "full/path/to/target/sysroot", ]

The sysroot will be located at target/sysroot and the target directory for building it at target/sysroot/target.

Due to how the rust sysroot works, you can use multiple different target specifications at a time without rebuilding, by simply passing a different --target to cargo.

Note that this tool is currently quite stupid, so it won't attempt to do anything if that file already exists. In this case you will have to edit it manually.

This will allow Cargo to properly build your project with the normal commands such as cargo build. You may wish to modify this file to make use of the target.$triple.runner key. See the Cargo Documentation for details. Note that the author experienced problems with the $triple variant not working, and you may experience better success with the cfg variant.

If you update your Rust nightly version you will need to run cargo-sysroot again. Note that doing this will cause cargo to detect that libcore has changed and rebuild your entire project.

Recommendations

If you have more complicated needs than can be satisfied by target.$triple.runner, which doesn't yet support passing arguments, the author recommends using a tool such as cargo-make.

Use my other crate, cargo-image to build an image suitable for running in QEMU.

Details

The sysroot crates are compiled with the --release switch. compiler_builtins is built with the mem and core features, which provides memcpy and related.

The sysroot crates will share any profile information your crate specifies. Eg if you enable debug for release, the sysroot crates will have that too. This matches cargo-xbuild behavior and is required for the bootloader crate to function.

TODO

• Allow specifying a custom rust-src.
• Allow disabling the mem feature.

FAQ

• Q: Why are all versions before 0.5.0 yanked?

• A: They didn't work correctly due to bugs or changes in the standard distribution.

• Q: Why did you write this over just using cargo-xbuild

• A: It was easier and simpler than getting cargo-xbuild to work reliably or with any other standard tools.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.