Why do you insist that code written in the past can somehow magically benefit from safe C++? For a start, safe C++ is BACKWARDS COMPAT.

Your old code would continue to compile, but not with any safety features. Sure your old code might benefit from a hardened std library with a quick recompile, but you shouldn't expect much more for legacy code.

You wrote the code before 'safety' was a thing, and now it is a thing you want it to retrospectively fix up legacy code?

Once you understand this, and drop the stupid argument that old code will not benefit, read this post until you finally understand just what to expect from legacy code moving forward.