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Subject: Re: cygwin qsort erratic
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From: Thomas Wolff <towo AT towo DOT net>
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Date: Mon, 31 Aug 2020 20:00:58 +0200
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Am 31.08.2020 um 19:50 schrieb Kurt-Karen Carlson-Lougheed via Cygwin:
> Brian,
> It's difficult to produce a simple test case with erratic behavior. I have
> wrapped my qsort invocations within a qqsort routine. I've attached
> qqsort.h which includes both the wrapper and the netbad qsort.c renamed as
> Qsort (and with _DIAGASSERT's commented out). Also attached is cygsort.txt
> which is script output demonstrating the problem. My apologies that is 200+
> lines, the Verbose mode states whether Qsort (netbsd) or qsort (cygwin) is
> being invoked, I added the '$' command to toggle back and forth. Descending
> sorts on the D/C (dpc) column have been most problematic. The descending
> '+S dpc' after the ascending '+s dpc' is the most graphic example. I did
> publish uac19 v3.3 on SourceForge this morning, or I can send somebody a
> tgz.
Kurt-Karen, this is hard to comprehend. It is common practice that 
someone who claims something is buggy, especially about something 
essential like qsort, should demonstrate that claim with a reproducible 
test case, even if, as you say, it may be difficult to produce one. If 
this happens in a series of invocations you have it should be possible 
to identify one case with wrong results and reproduce its input and 
invocation scenario.
Thomas

>
> Corinna,
> I'm a cygwin user and neither a cygwin nor netbsd developer. I do not know
> what newlib or 'git format-patch' are. If I had access to source for
> cygwin's qsort  I could probably devise a patch, but it's probably better
> for somebody familiar with the tools cygwin uses to do that. The attached
> qqsort.h is an easy geek read. That qsort works with Linux/RHEL7 and with
> netbsd's version under cygwin should make fixing it straight forward for
> somebody in the know.
>
> Regards, Kurt
>
> On Sun, Aug 30, 2020 at 7:55 PM Brian Inglis <
> Brian DOT Inglis AT systematicsw DOT ab DOT ca> wrote:
>
>> On 2020-08-30 15:27, Kurt-Karen Carlson-Lougheed via Cygwin wrote:
>>> In a small percentage of qsort requests, the results are erratic. Running
>>> the same code under Linux (RHEL7) does NOT have this problem. I updated
>> my
>>> cygwin to current and the problem persists. I copied the latest
>> netbsd.org
>>> qsort.c and compiled into my code, the problem is resolved with that
>>> version of qsort.
>>>
>>> In researching this issue, there was a post to this list 2015-01-11
>>> reporting a
>>> 'damaged' qsort. This may still be the same issue. The netbsd version I
>> am
>>> now using is dated 2017-05-19.
>>>
>>> My code experiencing this is SourceForge uac19, I'll be posting the
>>> corrected version (v3.2) with the netbsd qsort tomorrow after completing
>>> validation tests. I would ultimately like to see cygwin's qsort fixed.
>> As qsort depends on the array object data types and comparison functions,
>> please
>> post a Simple Test Case, showing at least those types and function(s), and
>> the
>> faulty output results.
>>
>> --
>> Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
>>
>> This email may be disturbing to some readers as it contains
>> too much technical detail. Reader discretion is advised.
>> [Data in IEC units and prefixes, physical quantities in SI.]
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