An OpenEmebdded/Yocto layer providing pre-built toolchains for the Rust programming language.

• meta-rust-bin
  • Basic Example
  • Features
    • Use with Yocto Release 4.0 (kirkstone) and Above
    • Use with Yocto Release 3.4 (honister) and Above
  • Advanced Features
    • Specifying Cargo Features
    • Using Components Individually
  • Pre-built vs. Compiled
  • Adding Support for New Versions
  • Copyright

A basic class for cargo-based executables is provided. The following is a simple recipe called gpio_utils.bb that builds the gpio-utils crate from branch master.

SUMMARY = "GPIO Utilities"
HOMEPAGE = "git:https://github.com/rust-embedded/gpio-utils"
LICENSE = "MIT"

inherit cargo

SRC_URI = "git:https://github.com/rust-embedded/gpio-utils.git;protocol=https;branch=master"
SRCREV="02b0658cd7e13e46f6b1a5de3fd9655711749759"
S = "${WORKDIR}/git"
LIC_FILES_CHKSUM = "file:https://LICENSE-MIT;md5=935a9b2a57ae70704d8125b9c0e39059"

As you can see, there is almost no overhead introduced from the cargo class beyond simply inheriting it. The cargo class adds the appropriate Rust dependencies as well as default compile and install steps.

Currently supported:

• Rust 1.71.0 (and many older, stable versions)
• x86 (32 and 64-bit), ARM (32 and 64-bit) build systems.
• All Linux architectures that Rust itself supports (Multiple flavors of: x86, ARM, PPC, and MIPS)
• Statically-linked libstd, dynamically-linked system libraries (libc, libm, etc)

Future:

• Building and installing dev and staticdev packages (i.e. allow build and install of static and dynamic library builds).
• Debug builds with separated debug info to allow gdbserver usage.
• Running Rust/Cargo on target.
• Vendoring of Cargo dependencies (to better play with the Yocto offline build model).
• Use of a shared libstd across all Rust packages on a target system (provides space savings).
• Total static linking using MUSL.

From Yocto version 4.0 network access from tasks is disabled by default on kernels which support this feature (on most recent distros such as CentOS 8 and Debian 11 onwards). The task do_compile need to access the network because it downloads dependencies, so add the following line to the recipe:

do_compile[network] = "1"

Rust is included directly in openmbedded-core as of Yocto version 3.4. The included recipe builds Rust components from the sources. To use binaries from the meta-rust-bin layer instead, set BBMASK to exclude the package in your configuration:

BBMASK = "poky/meta/recipes-devtools/rust"

Because Yocto is primarily used for embedded development, it is likely that projects will have differing features based on whether the crate is run on the hardware or in development on a PC. Cargo features can be easily specified by adding a space-separated list of CARGO_FEATURES to the recipe:

CARGO_FEATURES = "feature1 feature2"

Although the cargo class is the easiest way to use this layer, the components it provides may also be used directly. To add the Rust compiler plus target and host standard libraries to the environment, depend on or install rust-bin. To manually install cargo depend on or install cargo-bin.

Note that while there is nothing explicitly preventing the installation of Rust on the target, it hasn't been tested and is likely not to work. Pull requests are welcome!

This layer exists as a tradeoff against other options, e.g. the meta-rust project. Both exist to satisfy different requirements.

Because this layer uses the upstream compiled versions of Rust and Cargo, it will never be able to support architectures or options not supported by the Rust team itself.

Also, because this layer uses pre-built Rust standard libraries, it is possible that the standard libraries provided with this layer will be less efficient than code produced by a custom-compiled standard library.

However, using pre-built tools has advantages:

• Updating the layer to a new version of Rust is as easy as updating checksums and file names, so new versions of Rust are available quickly.
• In almost all modern systems, it is faster to download the binaries than it is to download source and build the Rust toolchain from scratch.
• Compatability across multiple versions of Yocto is maximized since only basic, stable recipe features are used.
• Trivial support for all architectures supported by upstream Rust.

When a new version of rust is released, adding support for this new version can be done by running build-new-version.sh as follows:

./build-new-version.sh <version>

This will create two new recipes:

• recipes-devtools/rust/rust-bin-.bb
• recipes-devtools/rust/cargo-bin-.bb

Where the cargo version generated is the one packaged with the associated release of rust itself (using the published channel data consumed by other tools like rustup).

For latest nightly version:

./build-new-version.sh nightly

For specified nightly version:

./build-new-version.sh nightly 2019-07-08

Copyright (c) 2016, the meta-rust-bin authors.

Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
https://www.apache.org/license/LICENSE-2.0> or the MIT license
<LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
option.  This file may not be copied, modified, or distributed
except according to those terms.