m02-resource

What the source does

• FilesystemNone observedNo reads or writes in the source
• NetworkNone observedNo outbound calls in the source
• ShellNone observedNo commands run in the source
• DependenciesPinnedNothing floats
• SecretsNone foundNo keys in source

Five audit layers

Gates applied: no behavioural pass, no license.

Audit 0.4.1 · source sha f4ff8c82542d · 28 Oct 2026Report an issue or request a re-scan

• Publisherzhanghandong GitHub organizationOwner of the repository this skill is read from
• Source folderzhanghandong/rust-skills/skills/m02-resourceThe exact folder we audited
• LicenceNot declaredAs the repository states it
• Commit pinned for this verdictf4ff8c82542dA new audit runs when the source changes
• Repository statusNot archivedLast push 65 days ago
• Sandboxed runNot runSkills are read, not executed; layer L4 is skipped

Its description: CRITICAL: Use for smart pointers and resource management. Triggers: Box, Rc, Arc, Weak, RefCell, Cell, smart pointer, heap allocation, reference counting, RAII, Drop, should I use Box or Rc, when to use Arc vs Rc, 智能指针,…

---
name: m02-resource
description: "CRITICAL: Use for smart pointers and resource management. Triggers: Box, Rc, Arc, Weak, RefCell, Cell, smart pointer, heap allocation, reference counting, RAII, Drop, should I use Box or Rc, when to use Arc vs Rc, 智能指针, 引用计数, 堆分配"
user-invocable: false
---

# Resource Management

> **Layer 1: Language Mechanics**

## Core Question

**What ownership pattern does this resource need?**

Before choosing a smart pointer, understand:
- Is ownership single or shared?
- Is access single-threaded or multi-threaded?
- Are there potential cycles?

---

## Error → Design Question

| Error | Don't Just Say | Ask Instead |
|-------|----------------|-------------|
| "Need heap allocation" | "Use Box" | Why can't this be on stack? |
| Rc memory leak | "Use Weak" | Is the cycle necessary in design? |
| RefCell panic | "Use try_borrow" | Is runtime check the right approach? |
| Arc overhead complaint | "Accept it" | Is multi-thread access actually needed? |

---

## Thinking Prompt

Before choosing a smart pointer:

1. **What's the ownership model?**
   - Single owner → Box or owned value
   - Shared ownership → Rc/Arc
   - Weak reference → Weak

2. **What's the thread context?**
   - Single-thread → Rc, Cell, RefCell
   - Multi-thread → Arc, Mutex, RwLock

3. **Are there cycles?**
   - Yes → One direction must be Weak
   - No → Regular Rc/Arc is fine

---

## Trace Up ↑

When pointer choice is unclear, trace to design:

```
"Should I use Arc or Rc?"
    ↑ Ask: Is this data shared across threads?
    ↑ Check: m07-concurrency (thread model)
    ↑ Check: domain-* (performance constraints)
```

| Situation | Trace To | Question |
|-----------|----------|----------|
| Rc vs Arc confusion | m07-concurrency | What's the concurrency model? |
| RefCell panics | m03-mutability | Is interior mutability right here? |
| Memory leaks | m12-lifecycle | Where should cleanup happen? |

---

## Trace Down ↓

From design to implementation:

```
"Need single-owner heap data"
    ↓ Use: Box<T>

"Need shared immutable data (single-thread)"
    ↓ Use: Rc<T>

"Need shared immutable data (multi-thread)"
    ↓ Use: Arc<T>

"Need to break reference cycle"
    ↓ Use: Weak<T>

"Need shared mutable data"
    ↓ Single-thread: Rc<RefCell<T>>
    ↓ Multi-thread: Arc<Mutex<T>> or Arc<RwLock<T>>
```

---

## Quick Reference

| Type | Ownership | Thread-Safe | Use When |
|------|-----------|-------------|----------|
| `Box<T>` | Single | Yes | Heap allocation, recursive types |
| `Rc<T>` | Shared | No | Single-thread shared ownership |
| `Arc<T>` | Shared | Yes | Multi-thread shared ownership |
| `Weak<T>` | Weak ref | Same as Rc/Arc | Break reference cycles |
| `Cell<T>` | Single | No | Interior mutability (Copy types) |
| `RefCell<T>` | Single | No | Interior mutability (runtime check) |

## Decision Flowchart

```
Need heap allocation?
├─ Yes → Single owner?
│        ├─ Yes → Box<T>
│        └─ No → Multi-thread?
│                ├─ Yes → Arc<T>
│                └─ No → Rc<T>
└─ No → Stack allocation (default)

Have reference cycles?
├─ Yes → Use Weak for one direction
└─ No → Regular Rc/Arc

Need interior mutability?
├─ Yes → Thread-safe needed?
│        ├─ Yes → Mutex<T> or RwLock<T>
│        └─ No → T: Copy? → Cell<T> : RefCell<T>
└─ No → Use &mut T
```

---

## Common Errors

| Problem | Cause | Fix |
|---------|-------|-----|
| Rc cycle leak | Mutual strong refs | Use Weak for one direction |
| RefCell panic | Borrow conflict at runtime | Use try_borrow or restructure |
| Arc overhead | Atomic ops in hot path | Consider Rc if single-threaded |
| Box unnecessary | Data fits on stack | Remove Box |

---

## Anti-Patterns

| Anti-Pattern | Why Bad | Better |
|--------------|---------|--------|
| Arc everywhere | Unnecessary atomic overhead | Use Rc for single-thread |
| RefCell everywhere | Runtime panics | Design clear ownership |
| Box for small types | Unnecessary allocation | Stack allocation |
| Ignore Weak for cycles | Memory leaks | Design parent-child with Weak |

---

## Related Skills

| When | See |
|------|-----|
| Ownership errors | m01-ownership |
| Interior mutability details | m03-mutability |
| Multi-thread context | m07-concurrency |
| Resource lifecycle | m12-lifecycle |

Excerpt, first 4,257 characters of SKILL.md, verbatim from the audited commit. It is text from someone else’s repository, quoted so you can judge it before your agent reads it.

git clone https://github.com/zhanghandong/rust-skills
git -C rust-skills checkout f4ff8c82542d

Works in

1. 2026-10-28
   ✓SAFE B 89 / 100

   first audit · source f4ff8c82542d

Questions about m02-resource

• github.com/zhanghandong/rust-skills/tree/main/skills/m02-resourc — the audited source at commit f4ff8c82542d and every finding aboveObserved · 28 Oct 2026

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