Practically all valid Rust can be rewritten as valid C++. To make C++ reject most invalid thread-based code that Rust rejects, you can mark cross-thread-shared

Practically all valid Rust can be rewritten as valid C++. To make C++ reject most invalid thread-based code that Rust rejects, you can mark cross-thread-shared references as const&, atomic fields as mutable, and write a Mutex<T> class which wraps a mutable T, and only allows accessing a T& through a Mutex const& by locking the mutex. So implementing Rust-style threading in C++ is viable, but extra work to write a Mutex<T>, and the compiler lacks borrow checking to prevent you from making lifetime and overlapping &/&mut mistakes and committing data races. (http://www.drdobbs.com/cpp/volatile-the-multithreaded-programmers-b/184403766 http://www.drdobbs.com/cpp/volatile-the-multithreaded-progra... proposes using volatile& for this purpose, but many regard this as actually a bad idea.) Though in practice most C++ codebases sprinkle mutexes ad-hoc, relying on at best comments describing what data is protected by what mutex, with predictably disastrous results. I feel Rust is a better language than C++ at implementing correct multithreaded code, but is so constraining that it makes correct single-threaded code hard to implement when it doesn't fit neatly into tree-shaped ownership (eg. graphs, GUI trees, and extending existing program architectures).