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Re: Broken autoconf mmap test (was Re: 1.7] BUG - GREP slows to a crawl with large number of matches on a single file)
- From: Ralph Hempel <rhempel at bmts dot com>
- To: cygwin at cygwin dot com, cygwin at cygwin dot com
- Date: Sun, 08 Nov 2009 10:51:56 -0500
- 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)
- References: <20091108141548.GB26344@calimero.vinschen.de>
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
I just found that the latest autoconf *still* has this broken test
for mmap, which basically calls
data2 = malloc (size);
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...
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