[astrange]

They're not unsafe (in the memory sense) as long as they check for overflow and reliably crash if there is one.

[naasking]

If a lot of platforms don't implement this check reliably, then it's unsafe in practice at this time, even if not in theory.

[astrange]

Who out there has a version of stack checking that doesn't actually check the stack…? If it doesn't check by default, as C doesn't, then it's not "as long as".