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[Python-Dev] checking "errno" for math operaton is safe to determine the error status?


VxWorks RTOS with 3rd party math lib.

Thanks,
Peixing


-----Original Message-----
From: Python-Dev [mailto:python-dev-bounces+peixing.xin=windriver.com at python.org] On Behalf Of Greg Ewing
Sent: Friday, April 12, 2019 1:45 PM
To: python-dev at python.org
Subject: Re: [Python-Dev] checking "errno" for math operaton is safe to determine the error status?

Xin, Peixing wrote:
> On certain platform, expm1() is implemented as exp() minus 1. To calculate
> expm1(-1420.0), that will call exp(-1420.0) then substract 1. You know,
> exp(-1420.0) will underflow to zero and errno is set to ERANGE. As a
> consequence the errno keeps set there when expm1() returns the correct result
> -1.

This sounds like a bug in that platform's implementation of
expm1() to me. Which platform is it?

-- 
Greg
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