Really annoying when people take 50 year old C code and modern C++ code and just drop them into the same bucket and refer to them as if they're the same thing. The CURL example they give has multiple modern C++ solutions that accomplish the same thing without UB.

I'm a / used to be a C++ programmer for 10 years. I've been lucky enough to work in a company that aims to adopt Rust. I have been working on Rust projects in the embedded space that runs on real-world devices right now for 3.5 years. Slowly but surely, not going into "rewrite every single thing now in Rust" but one component at a time when the project justifies it.

So, tell me what compiler option disables non-modern C++ code? Is there one that enforces that every single variable including stack ones work like unique_ptrs without paying the price?

How about safety checks in std; is there an opt-out style safety checks where I can ensure that I'm not adding random things to a map with the [] operator, the library checks size of vector when I access elements in non-performance-critical code, anybody can use iterators safely without being able to write code that can change contents of a container?

How about std::thread? Is there an enforcement switch that I can only pass in things that work exactly like trivially_constructible<T>s, unique_ptr<T>s or shared_ptr<mutex<T>>s and nothing else?

Is there a compiler switch that completely goes against https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines... and ensures that no unchecked pointer access happens without explicit approval from the developer?

If those all exist, is there a movement to port many of the core building block libraries to that special compiler including std without being afraid of breaking ABI?

Those are all what Rust developers (who were or still are quite advanced C++ devs, btw, not people who are afraid of using raw ptrs) get freely from the Rust compiler. A lot of "modern" C++ code still contains and, by design, cannot avoid creating unintended and unlimited UB.

This doesn't matter to the post, because it is about culture, not about code.

And there are plenty of ways to cause UB with modern C++ idioms.