xargo

Effortless cross compilation of Rust programs to custom bare-metal targets like ARM Cortex-M

The problem

To cross compile Rust programs one needs standard crates like libstd or libcore that have been cross compiled for the target. There are no official binaries of these crates for custom targets, the ones that need custom target specification files, so one needs to cross compile them manually. Furthermore, one needs to place these cross compiled crates in a specific directory layout, a sysroot, so they can be picked up by rustc when the --sysroot flag is passed. Finally, to use the sysroot with Cargo one needs to set the RUSTFLAGs variable to pass the --sysroot flag to each rustc invocation.

These are too many steps prone to subtle errors like compiling Rust source code that was checked out at a different commit hash than the one in rustc -V, etc. xargo makes the process straightforward by taking care of all these steps and requiring zero effort on your part!

Overview

xargo is a drop-in replacement for cargo . You can use it just like you would use cargo: with standard commands like xargo clean, or with custom commands like xargo fmt.

The magic happens when you call xargo with the --target flag. In that case, xargo will take care of building a sysroot with cross compiled crates and calling cargo build with the appropriate RUSTFLAGS variable. Example below:

xargo will cache the sysroot, so you can use it across different Cargo projects without having to build a sysroot for each project. xargo will also take care of rebuilding the sysroot when rustc is updated or when the target specification file is modified.

Caveats

• xargo only works with a nightly rustc/cargo.
• xargo will only build a sysroot for custom targets. For built-in targets (the ones in rustc --print target-list) you should install the standard crates via rustup.
• Only freestanding crates (the ones that don't depend on libc) are cross compiled for the target.
• xargo doesn't cross compile compiler-rt.
• xargo ignores custom targets when --target path/to/specification.json is used.

Dependencies

• cargo and rustc must be in $PATH
• Xargo depends on the cargo crate, which depends on libssh2-sys, which requires cmake and the OpenSSL headers to build.
  • On Fedora, run:
    • sudo dnf install cmake openssl-devel
  • On Ubuntu, run
    • sudo apt-get install cmake libssl-dev

Installation

cargo install xargo

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.