It's not necessarily a "miscompile". C is supposed to be portable to even completely stupid architectures, and on some architectures, just loading an invalid pointer value into a register will cause a trap, even if you don't dereference it. So on those machines, if x is NULL, then an unoptimized compile of ((size_t)(&x->y)) will result in code that crashes. So that's why it's undefined.
(I'm pretty sure POSIX does impose certain non-stupidity requirements on its underlying architecture, so there are things that are undefined in plain C that are guaranteed to work on any POSIX platform. But I don't know if this is one of them.)
> Do Any of those cited give specific timelines? Even if we are very far away, do you really doubt that one day machines will have superhuman intelligence? I take that as pretty much a given, whether it's 50 or 500 years from now
Why? If you extrapolate from the amount of progress we have made toward AGI in the last 50 years (ie, none), then it's reasonable to argue that we still will have made no progress 50 and 500 years from now.
There are intellectual problems that humans aren't capable of solving; it wouldn't make any sense to talk about "superhuman intelligence" if that wasn't the case. The currently available evidence suggests that "constructing an AGI" might very well be one of those problems.