[Python-Dev] VAX NaN evaluations (original) (raw)

John Klos john at ziaspace.com
Mon Nov 4 21:47:53 CET 2013

Hi,

The nice Python folks who were at SCALE in Los Angeles last year gave me a Python t-shirt for showing Python working on m68k and for suggesting that I'd get it working on VAX. With libffi support for VAX from Miod Vallat, this is now possible.

However, when compiling Python, it seems that attempts to evaluate NaN are made in test_complex.py, test_complex_args.py, test_float.py and test_math.py (at least in 2.7.5 - I'm working on compiling 3.3.2 now).

The short answer is to skip those tests on VAXen. The better answer is to patch any isnan functions to always return false on VAXen and patch any code which tries to parse, for instance, float("NaN") to use something uncommon, such as the largest representable number (const union __double_u __infinity = { { 0xff, 0x7f, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff } };) or something else equally rare. While code which depends on the ability to evaluate NaNs in some meaninful way will likely break on VAXen, I think this is better than raising an exception.

Being completely new to Python, I'm not sure what's best to do here. What would be the best way to find code which handles evaluation of "NaN"? Does anyone have any recommendations?

Thanks, John Klos

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