CRustS - Transpiling Unsafe C code to Safer Rust

Michael Ling, Yijun Yu, Haitao Wu, Yuan Wang, James R. Cordy, Ahmed E. Hassan 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

```bash

install c2rust

if [ $(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

cargo install crusts

elif [ $(uname -s) == "Linux" ]; then apt install llvm cmake clang libclang-dev bear -y LLVMLIBDIR=/usr/lib/llvm-14/lib/ cargo install c2rust curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh rustup override set nightly-2021-11-22-x8664-unknown-linux-gnu rustup component add rustfmt --toolchain nightly-2021-11-22-x8664-unknown-linux-gnu export PATH=$HOME/.local/bin:$HOME/.cargo/bin:$PATH

cargo install crusts

else

docker pull yijun/crusts

fi ```

Usage:

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

bash crusts [-v | -c2rust] or bash docker run -v $(pwd):/mnt -t yijun/crusts [-v | -c2rust]

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

References

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