In most languages, the language says nothing about what data is protected by the mutex. Modula and Ada did, and Java has "synchronized" objects, but C/C++/Go lack any syntax for talking about that. This typically becomes a problem as a program is modified over time, and the relationship between mutex and data is forgotten.
> In most languages, the language says nothing about what data is protected by the mutex.
Or the other way around, what mutex protects a piece of data (or even that a piece of data should be protected at all), so it's easy to forget it and just manipulate a bit of data without correctly locking it.
I was pleasantly surprised to discover that Rust's sync::Mutex owns the data it protects, so you can only access the data through the mutex (and the relation thus becomes obvious).
