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Date: Thu, 19 Jul 2007 09:50:30 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: CVS 1.7.0 heap errors
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On Jul 18 12:04, Corinna Vinschen wrote:
> On Jul 17 14:54, Brian Ford wrote:
> > > > On Wed, 27 Jun 2007, Corinna Vinschen wrote:
> > > You could also try to eliminate any change from
> > > http://cygwin.com/ml/cygwin-cvs/2007-q1/msg00139.html which is not
> > > related to your problem, [...]
> > 
> > You don't have any suggestions for how to best separate the patch into
> > pieces do you?
> 
> Look into the ChangeLog for the patch.  It can be divided into two
> different changes:
> 
> - Changing the cygheap->shared_prefix handling.
>   [...]
> 
> - Changing the way the user privileges are set at process startup.
> 
>   Affects dcrt0.cc, sec_helper.cc and security.h.
> 
>   Stupidly glaring at this change, I'm wondering if this is the culprit.
>   The change itself looks quite harmless.  But the non-obvious result
>   is that already very early in the process initialization functions from
>   advapi32 are called.  OTOH, Cygwin is load-time linked against advapi32.
>   So that shouldn't have any negative effect.  Hmm.

I found an actual bug in this patch.  I moved the call to
set_cygwin_privileges (hProcToken); at process initialization to a point
at which hProcToken wasn't even initialized.

  *hitting myself with a big stick*

Weird that it worked at all.

This *might* be the cause of the failing heap_init.  The problem is that
the calls to AdjustTokenPrivileges in set_privilege fail and
debug_printf is called (too?) early in process initialization, which in
turn results in dynamically loading user32.dll or some other Windows
DLL.  If this happens before the heap is initialized, there's a chance
that the Windows DLL reserves space which is needed for the heap.

What you could do to verify this:  Apply the patch from
http://cygwin.com/ml/cygwin-cvs/2007-q3/msg00039.html
to Cygwin from right after the patch from
http://cygwin.com/ml/cygwin-cvs/2007-q1/msg00139.html
and try if the heap problem still occurs.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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