CRustS - Transpiling Unsafe C code to Safer Rust

Michael Ling, Yijun Yu, Haitao Wu, Yuan Wang, James R. Cordy, Ahmed E. Hassan, Luca Carlig
Trustworthiness Software Engineering & Open Source Lab
Huawei Technologies, Inc.

As a safer alternative to C, Rust is a language for programming system software with a type-safe compiler to check its memory and concurrency safety. To facilitate a smooth transition from C to Rust in an existing project, and lay a solid foundation for an initial Rust re-implementation of existing functionalities in C, it would be helpful to have a source-to-source transpiler that can transform programs from C to Rust using program transformation technologies. However, existing C-to-Rust transformation tool sets have the drawback that they largely preserve the unsafe semantics of C, while rewriting them in Rust syntax. As such, the safety of the resulting Rust programs still depends primarily on the programmers, rather than on the Rust compiler. To gain more safety guarantees, in this demo, we present CRustS a systematic source-to-source transformation approach to increase the ratio of the code passing the safety checks of Rust compiler by relaxing the semantics-preserving constraints of the transformation. Our method uses 220 TXL source-to-source transformation rules, of which 198 are strictly semantics-preserving and 22 are semantics approximating, thus reducing the scope of unsafe expressions and exposing more opportunities for safe refactoring. Our method has been evaluated on both open-source and commercial projects. Our solution demonstrates significantly higher safe code ratios after the transformations, with function-level safe code ratios comparable to the average level of idiomatic Rust projects.

Compared to the Laertes[OOPSLA’21], with respect to their own benchmarks, the safe ratio obtained by CRustS is much higher.

Installation

# install c2rustif [ $(uname -s)=="Darwin" ];then
git clone https://github.com/immunant/c2rust cd c2rust
scripts/provision_mac.sh
cargo build --release
cp target/release/c2rust $HOME/.cargo/bin
cp target/release/c2rust-transpile $HOME/.cargo/bin
cp target/release/c2rust-analyze $HOME/.cargo/bin
cp target/release/c2rust-instrument $HOME/.cargo/bin
cd -
brew install bear
export PATH=$HOME/.local/bin:$HOME/.cargo/bin:$PATH
sh install_crown.sh
cargo install crusts
elif [ $(uname -s)=="Linux" ];then
apt install llvm cmake clang libclang-dev bear -y
LLVM_LIB_DIR=/usr/lib/llvm-14/lib/ cargo install c2rust
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
rustup override set nightly-2021-11-22-x86_64-unknown-linux-gnu
rustup component add rustfmt --toolchain nightly-2021-11-22-x86_64-unknown-linux-gnu
export PATH=$HOME/.local/bin:$HOME/.cargo/bin:$PATH
sh install_crown.sh
cargo install crusts
else
docker pull yijun/crusts
fi

Usage:

Run crusts in the folder where there is a Makefile, using

crusts

or

docker run -v $(pwd):/mnt -t yijun/crusts

As a result, Rust code will be generated from the C code:

src/*.rs -- contains transpiled and refactored Rust code from the C code;
Cargo.toml build.rs lib.rs -- contains the `cargo build` configurations;

Options

use crusts -h to see all the option and what they do

References

• Michael Ling, Yijun Yu, Haitao Wu, Yuan Wang, James Cordy, Ahmed Hassan. "In Rust We Trust: A transpiler from Unsafe C to Safer Rust", In: Proceedings of ICSE, 2022.
• Mehmet Emre, Ryan Schroeder, Kyle Dewey, and Ben Hardekopf. 2021. Translating C to safer Rust. Proc. ACM Program. Lang. 5, OOPSLA, Article 121 (October 2021), 29 pages. (code)
• TXL
• C2Rust
• Crown

Update

• comparing to Laertes
• integrating with docker for Windows users
• adding a switch -c2rust to turn off refactoring
• adding a switch -v to show versioning
• adding a switch -h to show help
• adding a switch -txl to implement customized txl rule
• bugfix: deref pointers, see test_unsafe
• bugfix: printf patterns, see test_stdio