Learn-skills.dev unsafe-checker

CRITICAL: Use for unsafe Rust code review and FFI. Triggers on: unsafe, raw pointer, FFI, extern, transmute, *mut, *const, union, #[repr(C)], libc, std::ffi, MaybeUninit, NonNull, SAFETY comment, soundness, undefined behavior, UB, safe wrapper, memory layout, bindgen, cbindgen, CString, CStr, 安全抽象, 裸指针, 外部函数接口, 内存布局, 不安全代码, FFI 绑定, 未定义行为

install

source · Clone the upstream repo

git clone https://github.com/NeverSight/learn-skills.dev

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/NeverSight/learn-skills.dev "$T" && mkdir -p ~/.claude/skills && cp -r "$T/data/skills-md/actionbook/rust-skills/unsafe-checker" ~/.claude/skills/neversight-learn-skills-dev-unsafe-checker && rm -rf "$T"

manifest: data/skills-md/actionbook/rust-skills/unsafe-checker/SKILL.md

source content

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

Common Errors

Error	Fix
Null pointer deref	Check for null before deref
Use after free	Ensure lifetime validity
Data race	Add proper synchronization
Alignment violation	Use `#[repr(C)]` , check alignment
Invalid bit pattern	Use `MaybeUninit`
Missing SAFETY comment	Add `// SAFETY:`

Deprecated → Better

Deprecated	Use Instead
`mem::uninitialized()`	`MaybeUninit<T>`
`mem::zeroed()` for refs	`MaybeUninit<T>`
Raw pointer arithmetic	`NonNull<T>` , `ptr::add`
`CString::new().unwrap().as_ptr()`	Store `CString` first
`static mut`	`AtomicT` or `Mutex`
Manual extern	`bindgen`

FFI Crates

Direction	Crate
C → Rust	bindgen
Rust → C	cbindgen
Python	PyO3
Node.js	napi-rs

Claude knows unsafe Rust. Focus on SAFETY comments and soundness.