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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)

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...

Cheers, Ralph

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