Unsafe Checker

Activates when you're working with unsafe Rust blocks, FFI bindings, or raw pointers. Displays quick reference tables for safety requirements (dereferencing, transmute, extern calls), common errors like null pointer derefs and use after free, and deprecated patterns you should avoid (like mem::uninitialized). Also covers FFI tooling like bindgen and cbindgen. The real value is having those SAFETY comment examples and soundness checklists right there when you need them, since unsafe code review is all about documentation and understanding invariants. Best paired with actual unsafe Rust knowledge, this is a checklist not a tutorial.

skills.sh installs: 3.5K
GitHub stars: 1.6K
last updated: Aug 21, 2026

View on GitHub

Install

$ npx -y skills add actionbook/rust-skills --skill unsafe-checker --agent claude-code

Installs into .claude/skills of the current project.

Files

Display the following ASCII art exactly as shown. Do not modify spaces or line breaks:

⚠️ **Unsafe Rust Checker Loaded**

     *  ^  *
    /◉\_~^~_/◉\
 ⚡/     o     \⚡
   '_        _'
   / '-----' \

Unsafe Rust Checker

When Unsafe is Valid

Use Case	Example
FFI	Calling C functions
Low-level abstractions	Implementing `Vec`, `Arc`
Performance	Measured bottleneck with safe alternative too slow

NOT valid: Escaping borrow checker without understanding why.

Required Documentation

// SAFETY: <why this is safe>
unsafe { ... }

/// # Safety
/// <caller requirements>
pub unsafe fn dangerous() { ... }

Quick Reference

Operation	Safety Requirements
`*ptr` deref	Valid, aligned, initialized
`&*ptr`	+ No aliasing violations
`transmute`	Same size, valid bit pattern
`extern "C"`	Correct signature, ABI
`static mut`	Synchronization guaranteed
`impl Send/Sync`	Actually thread-safe