[loeg]

I'm guessing you were asking about this part rather than UB in general:

> Except for the special case of unsigned char,

The SO article makes the bizarre claim that because

(1) an unsigned char, per the standard, cannot have any padding bits, it therefore cannot have a trap representation. And

(2) if it cannot have a trap representation, the use of an uninitialized value isn't undefined.

I'm willing to buy (1) but I don't remember (2) being required for UB. I think (2) is the step that is harder to follow intuitively. Admittedly, I have not read that part of the standard closely in some time.