Rust no_std

Purpose

Guide agents through #![no_std] Rust development: what core and alloc provide vs std, implementing custom global allocators, panic handler selection for embedded targets, and strategies for testing no_std crates on the host machine.

When to Use

Use this skill when writing or debugging #![no_std] Rust code — library crates for embedded targets, or bare-metal firmware that cannot link against std. For the full embedded development workflow (probe-rs flashing, defmt logging, RTIC), use skills/embedded/embedded-rust. For cross-compilation target setup, use skills/rust/rust-cross. This skill focuses specifically on the no_std / core / alloc boundary and panic handler selection.

Examples

• "I need a parser crate that works without std" → structure with #![no_std], feature-gate alloc APIs, use borrowed slices for core API
• "How do I use Vec in a no_std environment?" → add alloc feature, provide a global allocator (e.g., linked-list-allocator), use alloc::vec::Vec
• "How do I test my no_std crate on my laptop?" → use #![cfg_attr(not(test), no_std)] to allow std in test mode, or cargo test --target x86_64-unknown-linux-gnu

Workflow

1. no_std crate structure