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Date: Sat, 03 Feb 2018 10:13:38 +0200
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From: "Eli Zaretskii (eliz AT gnu DOT org) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
To: djgpp AT delorie DOT com
In-reply-to: <5A74B159.4020603@gmx.de> (djgpp@delorie.com)
Subject: Re: Fixing various bugs in frexp.S
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> Date: Fri, 02 Feb 2018 19:43:37 +0100
> From: "Juan Manuel Guerrero (juan DOT guerrero AT gmx DOT de) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
> 
> libc/ansi/math/frexp.S has simple bugs. It only returns correct
> values for normalized numbers and for positive zero.  Also in
> case of error it sets errno to EDOM and this is wrong as can be
> read in any man page of frexp.  Case of error means that the
> imput value is ether infinity or NaN.  For negative zero, +/- NaN
> and +/- infinity the values are simple wrong.  Below are the results
> as are generated by djdev205:

I believe all of those "bugs" are due to the fact that our libc was
developed when current versions of ANSI and Posix standards did not
yet exist.  We used much older versions of those standards, and the
above behavior matches what they said.

IOW, it's not like we didn't read "any man page of frexp", it's more
like those man pages used to say something different 20 years ago.