Comment by denzil

> So yes, it mostly gets done for (components of) planes, spacecraft, medical devices, etc.

I have to disagree here. All of these you mentioned have regularly bugs. Multiple spacecraft got lost because of these. For planes there's not so distant Boeing 737 MAX fiasco (admittedly this was bad software behavior caused by sensor failure). And medical devices, the news about their bugs semi-regularly pop up. So while the software for these might do a bit better than the rest, they certainly are not anywhere close to being bug free.

And same goes for specifications the software is based on. Those aren't bug-free either. And writing software based on flawed specification will inevitably result in flawed software.

That's not to say we should give up on trying to write bug free software. But we currently don't know how to do so.