How do I install the Unsafe Checker skill?

Run npx skillmds@latest add majiayu000/unsafe-checker in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Unsafe Checker safe to use?

This skill has not completed SkillMD's automated safety review yet. Independent scanners report: SkillSpector: PASS, Skill Scanner: PASS. Capability flags: docs only. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Unsafe Checker?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Unsafe Checker free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Unsafe Checker?

majiayu000 (@majiayu000) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Unsafe Checker by majiayu000 — Agent Skill

Name: Unsafe Checker
Rating: 4.5 (4 reviews)
Author: majiayu000

Unsafe Checker

Use when reviewing unsafe code or writing FFI. Keywords: unsafe, raw pointer, FFI, extern, transmute, *mut, *const, union, #[repr(C)], libc, std::ffi, MaybeUninit, NonNull, PhantomData, Send, Sync, SAFETY comment, soundness, undefined behavior, UB, how to call C functions, safe wrapper for unsafe code, when is unsafe necessary, memory layout, bindgen, cbindgen, CString, CStr, invariant, 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

majiayu000 Updated Sep 9, 2026 567 repo stars

File contents

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.

---name: unsafe-checkerdescription: Use when reviewing unsafe code or writing FFI. Keywords: unsafe, raw pointer, FFI, extern, transmute, *mut, *const, union, #[repr(C)], libc, std::ffi, MaybeUninit, NonNull, PhantomData, Send, Sync, SAFETY comment, soundness, undefined behavior, UB, how to call C functions, safe wrapper for unsafe code, when is unsafe necessary, memory layout, bindgen, cbindgen, CString, CStr, invariant, 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--- # 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 ```rust // 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.

Frequently asked questions