Rust's Slow Compile Times: A Deep Dive

2025-06-12

The slow feedback loop and long compilation times of Rust are frequent complaints. This blog post delves into the Rust compiler team's efforts to improve compilation speed and the challenges they face. While the team makes weekly progress, tackling performance improvements and regressions, and has achieved significant gains (e.g., nearly doubling speed on a specific benchmark in three years), near-instant compilation remains elusive due to technical hurdles and prioritization. These include the compiler's large and complex codebase, the need to balance various trade-offs in optimizations, maintaining stability, adding new features, and the limited time and resources of volunteer contributors. The post concludes by outlining future improvement directions, such as optimizing specific compilation workflows and performing large-scale refactoring of the compiler.

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Development Compiler Performance

Shrinking Rust's Target Directory: A New Compiler Flag

2025-06-02

Large target directories are a common frustration for Rust developers. This post introduces a new method to significantly reduce their size. A new compiler flag, `-Zembed-metadata=no`, combined with a new Cargo flag, `-Zno-embed-metadata`, prevents redundant metadata storage in `.rlib` and `.rmeta` files. Tests show a reduction of up to 36.3% in release mode. This feature is currently unstable (nightly), with plans to make it the default, but backward compatibility concerns need careful consideration.

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Development

Rust Compiler Error Messages: A Decade of Evolution

2025-05-16

This article explores the evolution of Rust compiler error messages over the past decade. By analyzing error outputs from various stable Rust releases, from 1.0 onwards, the author showcases significant improvements in clarity, readability, and user experience. Key milestones include the introduction of numerical error codes in 1.2.0 and colorful error messages with the `rustc --explain` hint in 1.26.0. The author highlights the continuous effort of hundreds of contributors, demonstrating the dedication to detail and iterative improvement within the Rust community. Minor, amusing inconsistencies across versions are also noted, underscoring the human element in this extensive undertaking.

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Development Error Messages

Rust Guiding Me Towards The Right Thing™

2025-03-30

While contributing to the Rust project bors, the author encountered a deployment issue caused by an SQL migration. The problem stemmed from adding a NOT NULL column to a populated table without providing a default value. The author not only fixed the bug but also leveraged Rust and the sqlparser crate to write an integration test that automatically detects such issues, showcasing Rust's strengths in encouraging high-quality code and preventing errors. The entire process was efficient and convenient, highlighting the benefits of Rust's powerful type system and IDE autocompletion.

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Development

A Cute Bug in HyperQueue: SIGTERM and the Ten-Second Mystery

2025-02-24

A curious bug emerged in HyperQueue, a Rust-based distributed task scheduler. Tasks, particularly those sleeping for more than 10 seconds, would mysteriously terminate. Debugging revealed a seemingly innocuous change: offloading process spawning to `tokio::task::spawn_blocking`. This, combined with `PR_SET_PDEATHSIG` (which sends SIGTERM upon parent process death), caused the issue. The worker thread spawned by `spawn_blocking` was being reaped by Tokio after inactivity, triggering the SIGTERM signal. The bug was fixed by reverting the optimization, highlighting the subtle interactions between concurrency, system calls, and thread management.

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Development