It would be good to merge it to 4.0 branch.
Would it be possible to expand on, or give some kind of pointer to, what "strict rules for overwriting polymorphic C++ objects" means?
Removed [no-] so hyperlink would work
lgtm with comment
e.g should be i.e. (or you could even spell it out: "that is")
I think it should also be "*the* vptr" and "*the* object* or "during an object's lifetime".
I also have sent it on the branch