C2Rust helps you migrate C99-compliant code to Rust. It provides:

• a C to Rust translator
• a Rust code refactoring tool
• tools to cross-check execution of the C code against the new Rust code

The translator (or transpiler), produces unsafe Rust code that closely mirrors the input C code. The primary goal of the translator is to produce code that is functionally identical to the input C code. Generating safe or idomatic Rust is not a goal for the translator. Rather, we think the best approach is to gradually rewrite the translated Rust code using dedicated refactoring tools. To this end, we are building a refactoring tool that rewrites unsafe auto-translated Rust into safer idioms.

Some refactoring will have to be done by hand which may introduce errors. We provide plugins for clang and rustc so you can compile and run two binaries and check that they behave identically (at the level of function calls). For details on cross-checking see the cross-checks directory and the cross checking tutorial.

Here's the big picture:

To learn more, check out our RustConf'18 talk on YouTube and try the C2Rust translator online at www.c2rust.com.

C2Rust requires LLVM 6 or 7 and its corresponding libraries and clang compiler. Python 3.4 or later, CMake 3.4.3 or later, and openssl (1.0) are also required. These prerequisites may be installed with the following commands, depending on your platform:

• Ubuntu 16.04, 18.04 & 18.10:

    apt install build-essential llvm-6.0 clang-6.0 libclang-6.0-dev cmake libssl-dev
  

• Arch Linux:

    pacman -S base-devel llvm clang cmake openssl
  

• OS X: XCode command-line tools and recent LLVM (we recommend the Homebrew version) are required.

    xcode-select --install
    brew install llvm python3 cmake openssl
  

Finally, a rust installation with Rustup is required on all platforms.

cargo build --release

This builds the c2rust tool in the target/release/ directory.

On OS X with Homebrew LLVM, you need to point the build system at the LLVM installation as follows:

LLVM_CONFIG_PATH=/usr/local/opt/llvm/bin/llvm-config cargo build

If you have trouble with cargo build, the developer docs provide more details on the build system.

To translate C files specified in compile_commands.json (see below), run the c2rust tool with the transpile subcommand:

c2rust transpile compile_commands.json

(The c2rust refactor tool is also available for refactoring Rust code, see refactoring).

The translator requires the exact compiler commands used to build the C code. To provide this information, you will need a standard compile_commands.json file. Many build systems can automatically generate this file, as it is used by many other tools, but see below for recommendations on how to generate this file for common build processes.

Once you have a compile_commands.json file describing the C build, translate the C code to Rust with the following command:

c2rust transpile path/to/compile_commands.json

To generate a Cargo.toml template for a Rust library, add the -e option:

c2rust transpile --emit-build-files path/to/compile_commands.json

To generate a Cargo.toml template for a Rust binary, do this:

c2rust transpile --main myprog path/to/compile_commands.json

Where --main myprog tells the transpiler to use the main method from myprog.rs as the entry point.

The translated Rust files will not depend directly on each other like normal Rust modules. They will export and import functions through the C API. These modules can be compiled together into a single static Rust library or binary.

There are several known limitations in this translator. The translator will emit a warning and attempt to skip function definitions that cannot be translated.

The compile_commands.json file can be automatically created using either cmake, intercept-build, or bear.

It may be a good idea to remove optimizations(-OX) from the compile commands file, as there are optimization builtins which we do not support translating.

When creating the initial build directory with cmake specify -DCMAKE_EXPORT_COMPILE_COMMANDS=1. This only works on projects configured to be built by cmake. This works on Linux and MacOS.

cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=1 ...

intercept-build (part of the scan-build tool) is recommended for non-cmake projects. intercept-build is bundled with clang under tools/scan-build-py but a standalone version can be easily installed via PIP with:

pip install scan-build

Usage:

intercept-build <build command>

You can also use intercept-build to generate a compilation database for compiling a single C file, for example:

intercept-build sh -c "cc program.c"

If you have bear installed, it can be used similarly to intercept-build:

bear <build command>

Are there release binaries? Can I install C2Rust with Cargo?

We plan to release a cargo package that you can cargo install soon(tm).

I translated code on platform X but it didn't work correctly on platform Y

We run the C preprocessor before translation to Rust. This specializes the code to the host platform. For this reason, we do not support cross compiling translated code at the moment.

What platforms can C2Rust be run on?

The translator and refactoring tool support both macOS and Linux. Other features, such as cross checking the functionality between C and Rust code, are currently limited to Linux hosts.

To report issues with the translation, please use our Issue Tracker.

The development team can be reached by email at [email protected].

This material is available under the BSD-3 style license as found in the LICENSE file.

The C2Rust translator is inspired by Jamey Sharp's Corrode translator. We rely on Emscripten's Relooper algorithm to translate arbitrary C control flows.

This material is based upon work supported by the United States Air Force and DARPA under Contract No. FA8750-15-C-0124. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the United States Air Force and DARPA. Distribution Statement A, “Approved for Public Release, Distribution Unlimited.”