Comparing Rust to Carbon

Summary

By Daroc AldenSeptember 16, 2025 RustConf Safe, ergonomic interoperability between Rust and C/C++ was a popular topic at RustConf 2025 in Seattle, Washington. Chandler Carruth gave a presentation about the different approaches to interoperability in Rust and Carbon, the experimental "(C++)++" language. His ultimate conclusion was that while Rust's ability to interface with other languages is expanding over time, it wouldn't offer a complete solution to C++ interoperability anytime soon — and so there is room for Carbon to take a different approach to incrementally upgrading existing C++ projects. His slides are available for readers wishing to study his example code in more detail. Many of the audience members seemed aware of Carbon, and so Carruth spent relatively little time explaining the motivation for the language. In short, Carbon is a project to create an alternative front-end for C++ that cuts out some of the language's more obscure syntax and enables better annotations for compiler-checked memory safety. Carbon is intended to be completely compatible with C++, so that existing C++ projects can be rewritten into Carbon on a file-by-file basis, ideally without changing the compiler or build system at all. Carbon is not yet usable — the contributors to the project are working on fleshing out some of the more complex details of the language, for reasons that Carruth's talk made clear. "It's always a little exciting to talk about a non-Rust programming language at RustConf," Carruth began, to general laughter. He has worked in C++ for many years, and has been working on Carbon since the project started in 2020. Currently, he is paid for his work on Carbon as part of Google's languages and compilers team. He briefly showed some research from Google indicating that the majority of the security vulnerabilities it deals with could have been prevented by memory-safe languages, but he didn't spend too long on it because he expected the audience of RustConf to be well-...