# What's New in Rust 1.81 through 1.84

Page: https://stenobird.com/podcast/rustacean-station/what-s-new-in-rust-1-81-through-1-84
Text version: https://stenobird.com/podcast/rustacean-station/what-s-new-in-rust-1-81-through-1-84.md
Podcast: [Rustacean Station](https://stenobird.com/podcast/rustacean-station)
Published: 2025-10-29T07:34:10+00:00
Episode link: https://rustacean-station.org/episode/rust-1.81-1.82-1.83-1.84/
Audio file: https://dts.podtrac.com/redirect.mp3/audio.rustacean-station.org/file/rustacean-station/2025-10-29-rust-1.81-1.82-1.83-1.84.mp3
Processing state: processed
JSON: https://stenobird.com/v1/public/podcasts/rustacean-station/episodes/what-s-new-in-rust-1-81-through-1-84
Duration seconds: 7394

## Resource

A deep dive into the technical evolution of Rust through releases 1.81 to 1.84. The discussion covers critical changes to the type system, attribute safety, and compiler optimizations.

## Highlights
- Main idea: The introduction of the Error trait to core allows for more robust error handling in no_std environments
- Practical takeaway: Use the new unsafe attribute syntax (e.g., #[unsafe(no_mangle)]) to explicitly denote attributes that can cause undefined behavior
- Failure mode: Misusing no_mangle across different modules can lead to linker conflicts and undefined behavior
- Technical insight: The new trait resolver is being leveraged to proactively fix long-standing soundness bugs in the language
- Optimization detail: Cargo is moving toward using file hashes instead of modification timestamps to prevent unnecessary recompilations

## Topics

Rust Programming Language, Compiler Theory, Memory Safety, Software Development, Error Handling, WebAssembly, Cargo Build System, Trait Resolution

## Chapters
- 1:00 — The Rapid Pace of Rust Releases: A discussion on the high frequency of Rust updates and the impact of the 1.0 milestone on the ecosystem.
- 10:35 — The Error Trait in Core: Analyzing the significance of bringing the Error trait to the core library for no_std development.
- 20:00 — Compiler Assertions and Soundness: How assertions act as axioms within the compiler's mathematical proving system to ensure soundness.
- 29:35 — WASM Target Transitions: The finalization of the transition from wasm32-wasi to the new naming scheme in version 1.84.
- 39:05 — Understanding Compilation Tiers: A breakdown of the different tiers of Rust support and the role of host tools.
- 48:35 — Pointer Coercion and Safety: Exploring the mechanics of converting between references and raw pointers.
- 57:40 — Encapsulating Unsafe Attributes: The introduction of the unsafe keyword within attributes like no_mangle to prevent memory safety violations.
- 1:43:55 — Cargo Performance Improvements: Moving from modification timestamps to content hashing to optimize build caching.

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## Transcript

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