# C To Rust Migration

> Complete C/C++ to Rust migration pipeline. Analyzes code difficulty, converts to idiomatic safe Rust, and validates the result. Covers memory management, pointer translation, error handling, unsafe minimization, and differential testing. Use when: migrate C to Rust, rewrite in Rust, C to Rust conversion, Rust migration, convert C code, C2Rust, unsafe Rust reduction.

- **Type:** Skill
- **Install:** `agentstack add skill-juanmarchetto-agent-skills-c-to-rust-migration`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [JuanMarchetto](https://agentstack.voostack.com/s/juanmarchetto)
- **Installs:** 0
- **Category:** [Web & Browser](https://agentstack.voostack.com/c/web-and-browser)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [JuanMarchetto](https://github.com/JuanMarchetto)
- **Source:** https://github.com/JuanMarchetto/agent-skills/tree/main/skills/c-to-rust-migration
- **Website:** https://github.com/JuanMarchetto/agent-skills

## Install

```sh
agentstack add skill-juanmarchetto-agent-skills-c-to-rust-migration
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# C to Rust Migration

Complete pipeline for migrating C/C++ codebases to safe, idiomatic Rust. Covers analysis, conversion, and validation in three phases.

## Pipeline

```
C/C++ Source
    |
Phase 1: ANALYZE
    | Classify difficulty (easy/medium/hard)
    | Detect patterns (pointers, macros, goto, unions)
    | Plan conversion strategy
    |
Phase 2: CONVERT
    | Apply migration patterns
    | Memory management → ownership/borrowing
    | Error codes → Result
    | Pointer arithmetic → slices/iterators
    | Quality gate: re-translate if >5 unsafe blocks
    |
Phase 3: VALIDATE
    | Compilation check (edition 2024)
    | Unsafe minimization (target: 0 for easy/medium)
    | Clippy with 0 warnings
    | Differential testing (same I/O as original C)
    | Idiomatic score calculation
    |
Safe, Idiomatic Rust
```

## Phase 1: Analysis

Classify each function by migration difficulty:

| Difficulty | Patterns | Strategy |
|---|---|---|
| **Easy** | Pure functions, simple arithmetic, no pointers, ` with `thiserror` |
| `NULL` checks | `Option` |
| Array + length params | Slices (`&[T]`) |
| `void*` | Generics or `enum` dispatch |
| Function pointers | `Fn` traits or enum dispatch |
| `struct` with `init`/`free` | `impl` with `new()` + `Drop` |
| Global mutable state | `OnceLock`, `Mutex`, or dependency injection |
| `goto` cleanup | `Drop` guards or `?` operator |

**Quality gate**: If translation produces >5 `unsafe` blocks, re-attempt with lower temperature (0.5) focusing on the unsafe sections.

See `references/conversion-patterns.md` for detailed examples from real migrations.

## Phase 3: Validation

Checklist (in order):

1. **Compilation**: `cargo build` with edition 2024, zero errors
2. **Clippy**: `cargo clippy` with zero warnings
3. **Unsafe audit**: Count `unsafe` blocks. Every one needs a `// SAFETY:` comment explaining why it's sound
4. **Differential testing**: Same inputs → same outputs as original C code
5. **Idiomatic score**: `(1 - unsafe_blocks/total_functions) * 0.4 + clippy_clean * 0.3 + has_tests * 0.2 + has_docs * 0.1`

**Quality floor**: Never accept a version that scores lower than the current best. If a fix attempt reduces the score, discard it.

See `references/validation-checklist.md` for the complete validation protocol.

## Example Output

```
C-to-Rust Migration Report — http_parser.c

Analysis:
  Total functions: 23
  Easy: 8 | Medium: 11 | Hard: 4
  Hard patterns: 2 goto statements, 1 union, 1 function pointer dispatch

Conversion:
  Functions migrated: 23/23
  Unsafe blocks: 2 (both in FFI boundary — justified)
  Idiomatic patterns applied: Result, Option, iterators, Drop guards

Validation:
  ✅ Compiles (edition 2024)
  ✅ Clippy: 0 warnings
  ✅ Unsafe: 2 blocks, both with SAFETY comments
  ✅ Diff tests: 47/47 passing (100%)
  Idiomatic score: 0.91/1.0

Quality: EXCELLENT — ready for production use
```

## Error Handling

- **C code doesn't compile**: Need the original build system info (Makefile, CMakeLists.txt) to understand dependencies and flags
- **Too many unsafe blocks**: Re-attempt conversion focusing on the unsafe sections. Consider if some are FFI boundaries (justified) vs unnecessary
- **Diff tests fail**: Compare output byte-by-byte. Common causes: endianness, floating point precision, uninitialized memory in C
- **Circular dependencies**: Rust doesn't allow circular module deps. Restructure with traits or merge modules

## Origin

Patterns extracted from real-world C-to-Rust migrations of open-source libraries: cJSON, genann, http-parser, picohttpparser, olive.c.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [JuanMarchetto](https://github.com/JuanMarchetto)
- **Source:** [JuanMarchetto/agent-skills](https://github.com/JuanMarchetto/agent-skills)
- **License:** MIT
- **Homepage:** https://github.com/JuanMarchetto/agent-skills

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-juanmarchetto-agent-skills-c-to-rust-migration
- Seller: https://agentstack.voostack.com/s/juanmarchetto
- Browse the marketplace: https://agentstack.voostack.com/browse

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