UB is part of the C++ standard. Surely you can understand the difference between the C++ standard and bugs in compilers implementing the C++ standard. This is that.

> I define undefined behaviour as a bug in C++. Now C++ is memory-safe!

I mean, sure, insofar as such a thing would also imply that a) the standard would need quite a bit of cleanup/clarification work to not contradict your definition, and b) the main optimizing C++ compilers are miscompiling code, analogous to how cve-rs is a rustc miscompilation rather than an issue with Rust itself.

(Fil-C might be an interesting exception here, though IIRC its definition of memory safety is slightly different)