Brad Gibson U007D

RustConf 2025
Rusty New 'ars talk
Seattle, WA
Presenter: Brad Gibson

Contact information:

ctx_error

Description

Ergonomic, static, contextual errors in Rust.

Details

What are Contextual Errors?

In a (typically larger) Rust program which is handling errors correctly, by default Rust does not capture the location (filename, line number and column number) where an Error was first emitted.

Raspberry Pi minimal image

This guide intends to summarize the essencial steps performed to build a Raspberry Pi minmal image using Yocto.

Download software dependencies

To build the image we are going to use the Poky and the layers meta-openembedded , meta-raspberrypi .

The list of all meta-raspberrypi dependencies are contained in the Readme.md the provided MACHINE's are listed on the layer-contentens.md

	Note: `mos-rust` is available via https://hub.docker.com. But if you're not on `amd64` and don't mind potentially stale builds
	(the docker image is 8 months old and 19,980 commits behind `llvm-mos` as of the time of this writing).

	# Installation
	## 1. Build & install `llvm-mos` to `/opt/llvm-mos`
	### macOS
	```fish
	sudo mkdir /opt/llvm-mos
	sudo chwown "$(whoami)" /opt/llvm-mos
	git clone https://github.com/llvm-mos/llvm-mos

	// This is a technique to emulate lifetime GATs (generic associated types) on stable rust starting
	// with rustc 1.33.
	//
	// I haven't seen this exact technique before, but I would be surprised if no one else came up with
	// it. I think this avoids most downsides of other lifetime GAT workarounds I've seen.
	//
	// In particular, neither implementing nor using traits with emulated lifetime GATs requires adding
	// any helper items. Only defining the trait requires a single helper trait (+ a single helper impl
	// for the 2nd variant) per GAT. This also makes the technique viable without any boilerplate
	// reducing macros.

	adapter speed 10000
	adapter driver ftdi

	ftdi_device_desc "Dual RS232-HS"
	ftdi_vid_pid 0x0403 0x6010
	ftdi_layout_init 0x0008 0x001b
	ftdi_layout_signal nSRST -oe 0x0020 -data 0x0020

	set _CHIPNAME riscv
	transport select jtag

	fn iterative_save<W: Write>(&self, mut wtr: W) -> Result<&Self> {
	for row in self {
	for (i, col) in row.iter().enumerate() {
	match i {
	0 => wtr.write_all(col.as_bytes())?,
	_ => {
	wtr.write_all(b",")?;
	wtr.write_all(col.as_bytes())?
	}
	}

	fn main() {
	let game = "X 7/ 9- X F8 ⑧/ F6 X X X8/"
	.chars()
	.filter(\|c\| !c.is_whitespace())
	.fold(Vec::new(), \|mut rolls, roll\| {
	match roll {
	'X' => rolls.push(10_u8),
	'/' => rolls.push(10 - rolls.last().expect("invalid game score")),
	c if c >= '0' && c <= '9' => rolls.push((u32::from(c) - 0x30) as u8),
	c if c >= '⑤' && c <= '⑧' => rolls.push((u32::from(c) - 0x245f) as u8),

	#![feature(existential_type)]
	use chrono::Local;
	use std::io::{self, Write};
	type Result<T> = std::result::Result<T, failure::Error>;

	trait IOutput {
	fn write(&self, content: &String) -> Result<()>;
	}

	struct ConsoleOutput {}

	using System;
	using Autofac;

	namespace DemoApp
	{
	// This interface helps decouple the concept of
	// "writing output" from the Console class. We
	// don't really "care" how the Write operation
	// happens, just that we can write.
	public interface IOutput