Date: Sun, 8 Nov 2009 11:11:19 -0500
From: Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Broken autoconf mmap test (was Re: 1.7] BUG - GREP slows to a  crawl with large number of matches on a single file)
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On Sun, Nov 08, 2009 at 10:51:56AM -0500, Ralph Hempel wrote:
>Corinna Vinschen wrote:
>> On Nov  8 14:56, Corinna Vinschen wrote:
>>> Btw., the check for mmap in grep's configure file is broken.  It tries
>>> to mmap to a fixed address formerly allocated via malloc().  This doesn't
>>> work on Windows.  An autoconf run with a newer version of autoconf would
>>> be nice.
>> 
>> I just found that the latest autoconf *still* has this broken test
>> for mmap, which basically calls
>> 
>>   data2 = malloc (size);
>>   mmap(data2, ...);
>> 
>> Why has this test never been fixed?  Chuck?
>
>I can't answer that question but this thread points out very important
>lessons in debugging specifically and projects in general.
>
>1. Easily reproducible test cases are critical to getting somone
>    interested in fixing your problem.
>
>2. Having the good fortune to have somebody run the test case and
>    duplicate the problem helps a bit more.
>
>3. Having that person challenge the assumptions under which the code
>    has been working for YEARS without a complaint helps a bit more.
>
>4. Having that person do a great analysis that shows why the problem
>    exists helps even more.
>
>5. Going even one step further and trying to figure out why the
>    problem has existed for years and what else might be wrong is
>    just the icing on the cake.
>
>Bravo Corinna - on a Sunday no less...

6. googling for the problem is always a good thing to do.

Once it was clear that this was a character set issue in grep it was
easy enough to find a fix since it was already in a couple of linux bug
trackers.

cgf

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