> I don’t mean this in a rude way but you should really read the posts I linked, it’s interesting and part 3 especially answers these questions

I have read the entire series. Both in the past and more recently.

> If you warned whenever undefined behaviour could be happening then e.g. every single pointer deference would say “warning: compiling assuming pointer is not null or unaligned”

I am not proposing that at all, I am proposing (which the series you link to does not preclude) that eliding code on the basis of UB can be determined by the compiler. If the compiler can determine that some code block needs to be elided, then the reason for that elision has already been determined, in which case it can issue a warning when "reason" == "pointer already used" when eliding the null check.