I understand that, what I am saying is, that the upper bound can never be useful because the lower bound is already so high that we cannot run U+1 steps, ever.
Hm, I'm not sure I would say that knowing an upper bound would be any help in solving these open problems, unless the way to prove that upper bound would involve a collatz type problem. We already know from the lower bound of BB(6) that we cannot iterate that far in this universe.
Blender is a tool that gives you a lot of options and some of those would be "wrong", so it is partly up to the user to know what is correct. The defaults have been "correct" for a long time already though, at least regarding linear vs gamma space.
Given that today is 6th Oct, I am gonna guess 06-10-2021 means today, and not the 10th of June. More often than not American dates would use a 06/10/2021 format, I think?
This seems to be missing a return in the NULL check for handle in the match_file function. This leads to fgets being called with a NULL pointer, which I don't know what it does, it may be OK.
I would argue that this is why a "better C" can be useful, it's the kind of error that would be much harder to make in rust.