that produced invalid operation when i tried it,
not the stack underflow of the previous example.
the result won't fit in a signed integer, and unsigned
integer isn't supported by the hardware, so you get a trap
as documented.  in fact,
the compiler could and probably should compensate by
converting to and from 64-bit signed integers,
which would also eliminate the test-and-skip mentioned earlier.
i think 64-bit is supported, since it's listed with an opcode,
although the textual description then claims `word- or short-integer format'
only.  it's an Intel handbook.  ``beware DEC manuals''

the stack underflow is more likely to be a compiler problem.
(stack overflow on the other hand is quite likely to be a missing prototype.)