BTW, I suspect that the reason there were no related test failures with the Intel compiler is that most of the problems in the Python code stem from multiplications rather than additions.  Probably icc isn't sophisticated enough to optimize those multiplication + division checks away.

Seems like we should probably be looking for an icc flag that forces wrapping on signed integer overflow.

In the long run, it would still be good to eliminate the need for fwrapv and the like;  it can have a significant performance hit (in theory;  haven't done any timings recently).