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• Last commit today
• 6 active contributors
• Distributed ownership (top contributor 49% of recent commits)
• Other licensed
• CI configured
• Tests present
• ⚠ Non-standard license (Other) — review terms

_{Computed from maintenance signals — commit recency, contributor breadth, bus factor, license, CI, tests}

C2Rust is an LLVM-based transpiler that automatically converts C99 code to unsafe Rust, preserving functionality while keeping close semantic fidelity to the original. It produces Rust code that compiles and passes existing C test suites, serving as a foundation for subsequent manual refactoring to safe Rust idioms. The project also includes analysis tools (c2rust-analyze) to automate unsafe-to-safe lifting and a refactoring tool (c2rust-refactor) to reduce manual migration effort. Cargo workspace (Cargo.toml lists 14 members) with distinct pipelines: c2rust-transpile handles C→Rust conversion, c2rust-analyze performs type/safety analysis (analysis/runtime with handler/metadata subsystems), c2rust-refactor provides interactive refactoring, and supporting crates (c2rust-ast-exporter for LLVM AST extraction, c2rust-asm-casts for inline asm, c2rust-macros for code generation). analysis/tests/ contains integration test projects (minimal, lighttpd, misc).

Systems engineers and teams migrating large C codebases (like lighttpd, tested in analysis/tests/) to Rust who need a mechanical translation preserving original behavior first, then safe Rust conversion later. Also security researchers using cross-checking features to verify translated code equivalence.

Actively developed and production-tested (v0.22.1, Rust 2021 edition, workspace with 14 crates). CI/CD present (.github/workflows/ci.yml and internal-testsuite.yml), extensive integration tests (analysis/tests includes real-world projects like lighttpd). Nightly Rust compiler pinned (nightly-2022-11-03 noted in README suggests active maintenance), but manual post-transpilation refactoring is still required for idiomatic Rust.

High complexity (4.5M lines of Rust, 220K+ lines of C++, multiple LLVM-dependent subsystems) creates significant maintenance burden. Requires LLVM 7+ and nightly Rust (not stable), adding version pinning friction. Analysis tooling (c2rust-analyze/) is explicitly stated as 'early stages' in README. Output is unsafe Rust requiring manual audit—no automatic safety guarantees. Single maintainer risk appears present (Immunant organization).

Active work on automated unsafe-to-safe lifting via c2rust-analyze (evidenced by comprehensive runtime handlers and PDG/data-flow analysis). CI covers both transpilation and internal test suite. Manual refactoring tool (c2rust-refactor) is documented but noted as early-stage. The Compiler Explorer integration (godbolt.org) is auto-updated nightly, indicating regular master branch activity.

curl -LsSf https://astral.sh/uv/install.sh | sh
uv venv && uv pip install -r scripts/requirements.txt
apt install build-essential llvm clang libclang-dev cmake libssl-dev pkg-config git  # Ubuntu/Debian
git clone https://github.com/immunant/c2rust.git
cd c2rust
cargo build --release

Daily commands:

cargo build --release
cargo run --bin c2rust -- transpile <c_file_or_config.json>
cargo test  # Run workspace tests
cd analysis/tests/minimal && cargo build  # Test integration on minimal example

• c2rust-analyze/src/main.rs — Entry point for c2rust-analyze, the primary tool that lifts unsafe Rust into safe types via dataflow and borrowck analysis.
• c2rust-transpile/src/main.rs — Entry point for the c2rust transpiler that converts C99 code to unsafe Rust, preserving functionality.
• c2rust-analyze/src/analyze.rs — Core analysis orchestration logic that drives the pointer safety and lifetime analysis passes.
• c2rust-analyze/src/rewrite/mod.rs — Rewrite engine that applies transformations to convert unsafe Rust patterns into safer, idiomatic code.
• c2rust-analyze/src/borrowck/mod.rs — Borrow checker implementation that models Rust's lifetime and mutability constraints for C pointer analysis.
• c2rust-analyze/src/dataflow/mod.rs — Dataflow analysis framework that tracks pointer usage patterns across the codebase.
• c2rust-analyze/src/pointee_type/mod.rs — Pointee type inference engine that determines safe Rust types for C pointers using constraint solving.

Add a new dataflow analysis pass

1. Define your analysis visitor/visitor logic in c2rust-analyze/src/dataflow/ following the pattern of existing passes (c2rust-analyze/src/dataflow/mod.rs)
2. Implement the analysis as a struct with methods that propagate facts forward/backward through the CFG (c2rust-analyze/src/dataflow/type_check.rs)
3. Register the pass in analyze.rs by adding it to the analysis pipeline (c2rust-analyze/src/analyze.rs)
4. Add test cases in c2rust-analyze/tests/ and verify output matches expectations (c2rust-analyze/tests/analyze.rs)

Add a new code rewrite transformation

1. Create a new rewrite rule as a struct in c2rust-analyze/src/rewrite/expr/ that matches unsafe patterns (c2rust-analyze/src/rewrite/expr/mod.rs)
2. Implement the transformation logic that generates safe Rust idioms (e.g., convert raw ptr deref to &T) (c2rust-analyze/src/rewrite/apply.rs)
3. Ensure the rewrite is scheduled in the rewrite orchestrator (c2rust-analyze/src/rewrite/mod.rs)
4. Add integration tests demonstrating the before/after transformation (c2rust-analyze/tests/analyze.rs)

Extend the C-to-Rust transpiler for new C constructs

1. Parse the new C construct in the AST exporter from clang (c2rust-ast-exporter/src/lib.rs)
2. Add Rust AST generation logic in c2rust-transpile to emit corresponding unsafe Rust (c2rust-transpile/src/main.rs)
3. Update the AST printer to correctly render the new Rust construct (c2rust-ast-printer/src/lib.rs)
4. Add test case in c2rust-transpile/tests/ with sample C code and expected Rust output (c2rust-transpile/tests)

Add support for a new safe Rust type pattern

1. Define how the type pattern should be recognized in the type inference engine (c2rust-analyze/src/pointee_type/mod.rs)
2. Add constraint formulation rules in constraint_set.rs for your pattern (c2rust-analyze/src/pointee_type/constraint_set.rs)
3. Ensure the solver correctly handles constraints for your type (c2rust-analyze/src/pointee_type/solve.rs)
4. Add rewrite rules to convert inferred pointers to your safe type (c2rust-analyze/src/rewrite/ty.rs)
5. Test with c2rust-analyze/tests/analyze/ cases that exercise your type pattern (c2rust-analyze/tests/analyze.rs)

• Rust + LLVM/Clang —

1. LLVM version pinning: requires LLVM 7+ and specific Rust nightly (nightly-2022-11-03 noted); updating breaks compatibility. 2) Workspace resolver='2' is required; older resolvers fail. 3) Output is unsafe Rust by design—transpiler does NOT produce safe code; you must manually refactor or use c2rust-analyze. 4) AST exporter is a separate C++ plugin requiring compilation; mismatch between clang and LLVM versions causes silent failures. 5) Python requirements.txt must be installed via uv; pip directly may miss pinned versions critical for tool compatibility.

• LLVM AST Extraction — C2Rust uses a custom clang plugin (c2rust-ast-exporter) to serialize the C AST before transpiling; understanding how AST is captured and serialized is essential for debugging transpilation failures
• Program Dependence Graph (PDG) — c2rust-analyze builds PDGs for data-flow analysis to identify which unsafe pointers can be safely converted to Rust references; referenced in analysis/tests/minimal/reference_pdg.bc
• Cross-Checking / Differential Testing — C2Rust includes runtime instrumentation (analysis/runtime/) to compare transpiled Rust output against original C behavior; critical for validating correctness without manual audits
• Unsafe Rust FFI & Lifetime Erasure — Transpiler must map C pointer semantics to Rust's ownership model; initial output uses raw pointers and unsafe blocks, which c2rust-analyze later refactors to safe types
• Bitfield Packing (via c2rust-bitfields-derive) — C bitfield structs have no direct Rust equivalent; custom derive macro in c2rust-bitfields-derive handles precise bit-layout preservation during transpilation
• Refactoring-Driven Transpilation (c2rust-refactor) — Interactive refactoring tool applies transformations post-transpilation; uses pattern matching on Rust AST to automate common safe conversion patterns (e.g., raw ptr → reference)

• mozilla/cbindgen — Generates Rust FFI bindings from C headers; complementary approach for C-Rust interop without full translation
• gnzlbg/abi_stable_crates — Provides stable ABI layer for Rust-C interop; useful for gradual migration where Rust and C coexist
• ferrocene/ferrocene — Rust compiler fork with formal verification support; relevant for high-assurance translation verification
• immunant/c2rust-examples — Companion repo with walkthroughs and example migrated codebases (if it exists; check GitHub org)

To work on one of these in Claude Code or Cursor, paste: Implement the "<title>" PR idea from CLAUDE.md, working through the checklist as the task list.

Add comprehensive test suite for c2rust-analyze borrowck module

The c2rust-analyze/src/borrowck/ directory contains critical analysis logic (atoms.rs, def_use.rs, type_check.rs, dump.rs) but there's no visible test directory. Given this is a core component for converting unsafe C patterns to safe Rust, unit tests would catch regressions and improve maintainability for contributors.

• [ ] Create c2rust-analyze/src/borrowck/tests/ directory with test modules
• [ ] Add unit tests for atoms.rs covering atom creation and manipulation
• [ ] Add integration tests in c2rust-analyze/tests/ that validate borrowck analysis on the existing test cases (minimal, misc, lighttpd-minimal)
• [ ] Update c2rust-analyze/README.md with borrowck testing documentation

Add CI workflow for analysis/runtime crate health checks

The analysis/runtime crate is a workspace member with handlers.rs, events.rs, and runtime backends, but there's no dedicated CI workflow visible beyond the generic ci.yml. Adding targeted checks (miri tests for UB detection, clippy lints, doc tests) would catch safety issues early since this runtime is injected into transpiled code.

• [ ] Create .github/workflows/analysis-runtime-ci.yml with miri and clippy checks
• [ ] Add doc tests to analysis/runtime/src/runtime/mod.rs explaining backend usage
• [ ] Add a safety-focused clippy configuration to .cargo/config.toml for analysis/runtime
• [ ] Document in analysis/runtime/README.md how to run local checks before submitting PRs

Extract and document PDG (Program Dependency Graph) API with examples

The pdg/ workspace member exists but has no visible documentation or examples in the file structure. The internal-testsuite.yml references PDG functionality, suggesting it's core to the analyze pipeline. New contributors need a clear API guide and worked examples to extend analysis passes.

• [ ] Create pdg/README.md documenting the PDG construction and traversal API
• [ ] Add pdg/examples/ directory with 1-2 minimal examples (e.g., 'build_pdg_from_c.rs', 'traverse_dataflow.rs')
• [ ] Add doc comments and examples to pdg/src/lib.rs (or main module file) showing how to use PDG in analysis
• [ ] Link PDG examples from c2rust-analyze/README.md in a 'extending the analyzer' section

• Add integration tests for c2rust-bitfields and c2rust-bitfields-derive: these crates are in workspace but analysis/tests/ has no dedicated test case for bitfield handling. Create analysis/tests/bitfields/ with C structs using bit-packed fields and verify transpilation accuracy.
• Document and test the c2rust-asm-casts crate: workspace includes it but no README or examples show inline assembly casting patterns. Add examples/ directory with annotated C code using asm() and verify generated Rust matches.
• Expand cross-checking examples: cross-checks/ is mentioned in README but no examples in analysis/tests/. Add a test case showing original C compiled alongside transpiled Rust with runtime instrumentation validating output equivalence.

The c2rust project is a sophisticated C-to-Rust transpiler with intentional unsafe code generation for migration purposes. Key security concerns include: (1) large volumes of intentionally-generated unsafe code requiring rigorous review, (2) use of outdated and nightly Rust toolchain versions with potential known vulnerabilities, (3) significant FFI attack surface for C code parsing, and (4) potential transitive dependency vulnerabilities. The project should prioritize modernizing the Rust toolchain, implementing comprehensive unsafe code auditing, adding fuzzing for the C parser, and establishing regular security review processes. The codebase shows good structural practices with workspace organization and CI/CD integration, but security hardening in the unsafe code generation and dependency management is recommended.

• Medium · Unsafe Code in C2Rust Transpiler — c2rust-transpile/, analysis/runtime/src/. The c2rust-transpile module explicitly generates unsafe Rust code as part of its core functionality. While this is intentional for C code migration, it creates a large surface area of unsafe code that requires careful review and testing to ensure memory safety properties are maintained. Fix: Implement comprehensive unsafe code auditing, add SAFETY comments documenting unsafe blocks, use miri for additional validation, and maintain a detailed unsafe code inventory with regular security reviews.
• Medium · Nightly Rust Dependency — c2rust-analyze/rust-toolchain.toml. The project specifies a pinned nightly Rust version (nightly-2022-11-03) in rust-toolchain.toml. Nightly Rust is unstable and may have unvetted security changes. The specified version is significantly outdated (from 2022), which may contain known vulnerabilities. Fix: Evaluate migration to stable Rust toolchain. If nightly is required, regularly update to the latest nightly version and document the specific features requiring nightly.
• Medium · Outdated Rust Minimum Version — Cargo.toml (rust-version = "1.67"). The project specifies MSRV (Minimum Supported Rust Version) as 1.67, which is significantly outdated. This may include known security vulnerabilities in the Rust compiler and standard library. Fix: Update MSRV to a recent stable version (1.75+) and test thoroughly. Document any breaking changes for users with older Rust versions.
• Low · Lack of Dependency Version Pinning — Cargo.toml, Cargo.lock (workspace level). The workspace Cargo.toml does not show explicit dependency version constraints visible in the provided snippet. Dependency vulnerabilities could be introduced through transitive dependencies without explicit pinning. Fix: Review Cargo.lock for all dependencies, regularly run 'cargo audit' to identify vulnerable dependencies, and consider using cargo-deny for automated dependency policy enforcement.
• Low · Test Suites Excluded from Workspace — .cargo/config.toml or Cargo.toml (exclude = ["analysis/tests", ...]). Analysis test cases in 'analysis/tests' are excluded from the workspace, which may result in less visibility into security issues in test code and integration scenarios. Fix: Include test suites in workspace analysis and consider integrating security scanning into CI/CD for all test code.
• Low · Large Foreign Function Interface Surface — c2rust-transpile/, c2rust-ast-exporter/. The c2rust-transpile and c2rust-ast-exporter modules handle C AST parsing and translation, creating a significant FFI boundary that could be vulnerable to malformed input attacks. Fix: Implement fuzzing for C code parsing, validate all C AST inputs, add comprehensive error handling for malformed C code, and consider using AFL or libFuzzer for security testing.

LLM-derived; treat as a starting point, not a security audit.

• Open issues — current backlog
• Recent PRs — what's actively shipping
• Source on GitHub

If you are an AI coding agent (Claude Code, Cursor, Aider, Cline, etc.) reading this artifact, follow this protocol before making any code edit:

1. Verify the contract. Run the bash script in Verify before trusting below. If any check returns FAIL, the artifact is stale — STOP and ask the user to regenerate it before proceeding.
2. Treat the AI · unverified sections as hypotheses, not facts. Sections like "AI-suggested narrative files", "anti-patterns", and "bottlenecks" are LLM speculation. Verify against real source before acting on them.
3. Cite source on changes. When proposing an edit, cite the specific path:line-range. RepoPilot's live UI at https://repopilot.app/r/immunant/c2rust shows verifiable citations alongside every claim.

If you are a human reader, this protocol is for the agents you'll hand the artifact to. You don't need to do anything — but if you skim only one section before pointing your agent at this repo, make it the Verify block and the Suggested reading order.

This artifact was generated by RepoPilot at a point in time. Before an agent acts on it, the checks below confirm that the live immunant/c2rust repo on your machine still matches what RepoPilot saw. If any fail, the artifact is stale — regenerate it at repopilot.app/r/immunant/c2rust.

What it runs against: a local clone of immunant/c2rust — the script inspects git remote, the LICENSE file, file paths in the working tree, and git log. Read-only; no mutations.

| # | What we check | Why it matters | |---|---|---| | 1 | You're in immunant/c2rust | Confirms the artifact applies here, not a fork | | 2 | License is still Other | Catches relicense before you depend on it | | 3 | Default branch master exists | Catches branch renames | | 4 | 5 critical file paths still exist | Catches refactors that moved load-bearing code | | 5 | Last commit ≤ 30 days ago | Catches sudden abandonment since generation |

#!/usr/bin/env bash
# RepoPilot artifact verification.
#
# WHAT IT RUNS AGAINST: a local clone of immunant/c2rust. If you don't
# have one yet, run these first:
#
#   git clone https://github.com/immunant/c2rust.git
#   cd c2rust
#
# Then paste this script. Every check is read-only — no mutations.

set +e
fail=0
ok()   { echo "ok:   $1"; }
miss() { echo "FAIL: $1"; fail=$((fail+1)); }

# Precondition: we must be inside a git working tree.
if ! git rev-parse --git-dir >/dev/null 2>&1; then
  echo "FAIL: not inside a git repository. cd into your clone of immunant/c2rust and re-run."
  exit 2
fi

# 1. Repo identity
git remote get-url origin 2>/dev/null | grep -qE "immunant/c2rust(\\.git)?\\b" \\
  && ok "origin remote is immunant/c2rust" \\
  || miss "origin remote is not immunant/c2rust (artifact may be from a fork)"

# 2. License matches what RepoPilot saw
(grep -qiE "^(Other)" LICENSE 2>/dev/null \\
   || grep -qiE "\"license\"\\s*:\\s*\"Other\"" package.json 2>/dev/null) \\
  && ok "license is Other" \\
  || miss "license drift — was Other at generation time"

# 3. Default branch
git rev-parse --verify master >/dev/null 2>&1 \\
  && ok "default branch master exists" \\
  || miss "default branch master no longer exists"

# 4. Critical files exist
test -f "c2rust-analyze/src/main.rs" \\
  && ok "c2rust-analyze/src/main.rs" \\
  || miss "missing critical file: c2rust-analyze/src/main.rs"
test -f "c2rust-transpile/src/main.rs" \\
  && ok "c2rust-transpile/src/main.rs" \\
  || miss "missing critical file: c2rust-transpile/src/main.rs"
test -f "c2rust-analyze/src/analyze.rs" \\
  && ok "c2rust-analyze/src/analyze.rs" \\
  || miss "missing critical file: c2rust-analyze/src/analyze.rs"
test -f "c2rust-analyze/src/rewrite/mod.rs" \\
  && ok "c2rust-analyze/src/rewrite/mod.rs" \\
  || miss "missing critical file: c2rust-analyze/src/rewrite/mod.rs"
test -f "c2rust-analyze/src/borrowck/mod.rs" \\
  && ok "c2rust-analyze/src/borrowck/mod.rs" \\
  || miss "missing critical file: c2rust-analyze/src/borrowck/mod.rs"

# 5. Repo recency
days_since_last=$(( ( $(date +%s) - $(git log -1 --format=%at 2>/dev/null || echo 0) ) / 86400 ))
if [ "$days_since_last" -le 30 ]; then
  ok "last commit was $days_since_last days ago (artifact saw ~0d)"
else
  miss "last commit was $days_since_last days ago — artifact may be stale"
fi

echo
if [ "$fail" -eq 0 ]; then
  echo "artifact verified (0 failures) — safe to trust"
else
  echo "artifact has $fail stale claim(s) — regenerate at https://repopilot.app/r/immunant/c2rust"
  exit 1
fi

Each check prints ok: or FAIL:. The script exits non-zero if anything failed, so it composes cleanly into agent loops (./verify.sh || regenerate-and-retry).

Generated by RepoPilot. Verdict based on maintenance signals — see the live page for receipts. Re-run on a new commit to refresh.