unsafe-checker

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.