Horton

RE: power() function in Windows: "value out of range: underflow"

Huong Dangminh <huo-dangminh@ys.jp.nec.com>

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From: Huong Dangminh <huo-dangminh@ys.jp.nec.com>
To: Euler Taveira <euler@timbira.com.br>
Cc: "pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>, "Pg Hackers" <pgsql-hackers@postgresql.org>, Akio Iwaasa <aki-iwaasa@vt.jp.nec.com>
Date: 2018-04-10T23:46:49Z
Lists: pgsql-bugs, pgsql-hackers 
Hi,
Thanks for response

# I will add this thread to current CF soon.

> 2018-04-10 5:30 GMT-03:00 Huong Dangminh <huo-dangminh@ys.jp.nec.com>:
> > There are some cases that power() function does not work correctly
> > with 'NaN' arguments in Windows environment.
> > Something like,
> >
> What is your exact OS version? What is your postgres version? I tested with
> Windows 10 (10.0.16299) x64 and couldn't reproduce the error.

I think it is not depended on OS version but the visual c++ runtime libraries version 
(It seem also be included in installers).

My environment:
====================================

- PostgreSQL: 9.6.8
  # I am using the EDB PostgreSQL Installer
  # It also can reproduce in PostgreSQL 10.3 or 9.5.12

  >postgres -V
  postgres (PostgreSQL) 9.6.8

  >psql -c "select version()"
                             version
  -------------------------------------------------------------
   PostgreSQL 9.6.8, compiled by Visual C++ build 1800, 64-bit
  (1 row)

  >psql -c "select 'NaN'^11"
  ERROR:  value out of range: underflow

- OS: Microsoft Windows 10 Pro 10.0.14393 build 14393

=============================

> > postgres=# select power('NaN',11);
> > ERROR:  value out of range: underflow
> > postgres=# select power('NaN','NaN');
> > ERROR:  value out of range: underflow
> > postgres=# select power(11,'NaN');
> > ERROR:  value out of range: underflow
> >
> > In Linux environment, instead of ERROR it returns 'NaN'.
> >
> Could you show us a simple test case? Print arguments, result and errno.

It just is my confirmation when debug PostgreSQL in Windows environment.
# I built PostgreSQL with VC++ 2012 in debug mode and confirmed.
I don't know how to print those values.


---
Thanks and best regards,
Dang Minh Huong
NEC Solution Innovators, Ltd.
http://www.nec-solutioninnovators.co.jp/en/

Commits

  1. Revert back-branch changes in power()'s behavior for NaN inputs.

  2. Avoid wrong results for power() with NaN input on more platforms.

  3. Avoid wrong results for power() with NaN input on some platforms.