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Message-ID: <5543C3C5.1060003@dronecode.org.uk>
Date: Fri, 01 May 2015 19:19:49 +0100
From: Jon TURNEY <jon DOT turney AT dronecode DOT org DOT uk>
Reply-To: cygwin AT cygwin DOT com
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To: Ken Brown <kbrown AT cornell DOT edu>, cygwin AT cygwin DOT com
Subject: Re: [ANNOUNCEMENT] Updated: xorg-server-1.17.1-3
References: <announce DOT 55411449 DOT 7020106 AT dronecode DOT org DOT uk> <5542AA7E DOT 5070504 AT cornell DOT edu> <55436A0A DOT 2010603 AT dronecode DOT org DOT uk> <554374FF DOT 7060708 AT cornell DOT edu>
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On 01/05/2015 13:43, Ken Brown wrote:
> On 5/1/2015 7:56 AM, Jon TURNEY wrote:
>> On 30/04/2015 23:19, Ken Brown wrote:
>>> On 4/29/2015 1:26 PM, Jon TURNEY wrote:
>>>>
>>>> The following packages have been updated in the Cygwin distribution:
>>>>
>>>> *** xorg-server-*1.17.1-3
>>>
>>> I'm finding, on three different 64-bit Cygwin systems, that the server
>>> dies shortly after starting.  I'm attaching XWin.0.log from one of them.
>>>   The log from a 32-bit Cygwin install on the same machine starts the
>>> same but then continues with
>>>
>>> [440201.140] winPointerWarpCursor - Discarding first warp: 640 512
>>> [440201.140] (--) 8 mouse buttons found
>>> [440201.140] (--) Setting autorepeat to delay=500, rate=31
>>> [...]
>>>
>>> The problem goes away if I revert to 1.17.1-2.  Let me know if there's
>>> further information that I can provide.
>>
>> That is rather mysterious and disappointing.  I can't reproduce this.
>>
>> Does this occur if you run XWin directly?
>
> Yes.
>
>> If so, could you perhaps upload a strace somewhere, please?
>
> http://sanibeltranquility.com/cygwin/xwin.trace.xz

Thanks.

This ends with ...

--- Process 2996, exception c0000005 at 0000000180155C82

and...

$ addr2line -e /usr/lib/debug/usr/bin/cygwin1.dbg 0x0000000180155C82
/usr/src/debug/cygwin-2.0.1-1/winsup/cygwin/malloc.cc:4753

... which is somewhere inside free().

I don't quite understand why cygwin's exception processing doesn't then 
catch that exception and raise a SIGSEGV.

However, I did a bit more staring at the changes in 1.17.1-3 and I did 
find a nasty bug in some code which uses the heap.  I've uploaded a 
snapshot [1] with a possible fix, please test that if you can.

[1] 
ftp://cygwin.com/pub/cygwinx/x86_64/XWin.20150501-git-b17931db63a48948.exe.bz2

-- 
Jon TURNEY
Volunteer Cygwin/X X Server maintainer

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