> What makes UB in C++ is spelled out in its International Standard That's not true, the standard only specifies that some things are UB, it is not exhaustive,

> What makes UB in C++ is spelled out in its International Standard That's not true, the standard only specifies that some things are UB, it is not exhaustive, nor is it unambiguous. Furthermore, no current C++ compiler is compliant even with those parts of the standard which everyone agrees on (eg. see proposals to introduce a "bytes" type to LLVM to resolve known miscompilations). There is work to improve this, such as defining an explicit memory model, but Rust is ahead of C++ on this. > In fact today C++ lifetimes are expressed in the type system, and this is an example of what C++ enables a library to provide. Do you have an example of this, or are you talking about using smart pointers? Smart pointers are about ownership, not lifetimes. > Your remarks suggest that libraries you delivered were closer to C than C++. Most of my remarks were about consuming other libraries from my library, which is not something I have control over. Sure, I can use smart pointers and other modern C++ features in the API I expose... That doesn't change any of the points I mentioned.