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Date: Tue, 26 Mar 2013 09:32:35 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: possible issue withC  formatted input/output
Message-ID: <20130326083235.GB16882@calimero.vinschen.de>
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References: <5150B737 DOT 3020800 AT quicknet DOT nl>
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User-Agent: Mutt/1.5.21 (2010-09-15)

On Mar 25 21:44, a DOT rburgers AT quicknet DOT nl wrote:
> While preparing gsl packages, one of the check fails.
> The failure is reproduced by attached .c file, which writes
> doubles to a file, and reads them back.
> 
> On linux this is the output (all zero differences in the last column).
> 
> ivals[0]=1: 0.002518891687657430663 0.002518891687657430663 0
> ivals[1]=6: 0.01511335012594458398 0.01511335012594458398 0
> ivals[2]=41: 0.1032745591939546598 0.1032745591939546598 0
> ivals[3]=45: 0.113350125944584379 0.113350125944584379 0
> ivals[4]=46: 0.1158690176322418192 0.1158690176322418192 0
> dawn.ad.intra{~/tmp }75: uname -a
> Linux dawn.ad.intra 2.6.9-89.31.1.ELsmp #1 SMP Mon Oct 4 21:41:59
> EDT 2010 x86_64 x86_64 x86_64 GNU/Linux
> 
> on cygwin (both 32 and 64 bit):
> 
> $ ./tst
> ivals[0]=1: 0.002518891687657430663 0.002518891687657430663 0
> ivals[1]=6: 0.01511335012594458398 0.01511335012594458224 1.7347e-18
> ivals[2]=41: 0.1032745591939546598 0.1032745591939546459 1.3878e-17
> ivals[3]=45: 0.113350125944584379 0.1133501259445843651 1.3878e-17
> ivals[4]=46: 0.1158690176322418192 0.1158690176322418053 1.3878e-17
> 
> the gsl test expects 0 differences and reports a fail.
> I am not sure whether this is a bug.  Maybe something with
> extended precision registers, when I wild guess.

Thanks for the testcase.  This problem has been introduced in newlib a
while back and made it into 1.7.17, unfortunately.  However, it's fixed
in the latest snapshots from http://cygwin.com/snapshots/ and will be in
1.7.18.


Corinna

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Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
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