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From: David Rothenberger <daveroth AT acm DOT org>
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Date: Fri, 8 Aug 2003 11:18:23 -0700
To: cygwin AT cygwin DOT com
Subject: Re: What is the minimum needed to run gtar?
In-Reply-To: <20030808173549.GE9351@redhat.com>
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Reply-To: cygwin AT cygwin DOT com

Christopher Faylor writes:
 > On Fri, Aug 08, 2003 at 09:12:45AM -0700, David Rothenberger wrote:
 > >David Rothenberger wrote:
 > >> 
 > >> David Rothenberger writes:
 > >>  > "Biederman, Steve" wrote:
 > >>  > >
 > >>  > > I want to allow the users I support to be able to run Cygwin tar on their Windows machines.
 > >>  > > These machines have not had any Cygwin installed; they're just bare Windows machines.
 > >>  > >
 > >>  > > I provided them tar.exe and cygwin1.dll and assumed that with these, they could run
 > >>  > > Cygwin tar sucessfully.  It appears that that isn't the case: machines without Cygwin
 > >>  > > installed see different behavior than machines which have it installed.  (Running tar
 > >>  > > on machines without Cygwin installed creates incorrect tar archives.)
 > >>  >
 > >> [snip]
 > >>  > Through experimentation, I discovered that the problem went away if I
 > >>  > created an /etc mount.
 > >> 
 > >> I did a little debugging on this.  It turns out that when tar
 > >> "hangs", the process is in an infinite loop in malloc_consolidate().
 > >
 > >Some googling uncovered that loops in malloc_consolidate() are usually a
 > >sign of heap corruption.  More googling suggested that compiling the
 > >cygwin dll with --enable-malloc-debugging would be helpful for finding
 > >heap corruption.  But, I'm have quite a bit of trouble getting the dll
 > >to compile with that configure switch.
 > 
 > That's because it is currently broken.  There was a hack posted to get it
 > working.  I think it was to the cygwin mailing list.

I came up with a different hack to get it working enough for my
purposes.  After reading the thread Chris mentioned, I don't think
I'll submit those changes as a patch.

Enabling malloc debugging did allow me to find the source of the
heap corruption that was breaking tar.  I'll submit the patch to fix
it shortly.

Dave


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