X-Spam-Check-By:	sourceware.org
Date:	Thu, 30 Mar 2006 01:35:54 +0200
Message-Id:	<469738104@web.de>
MIME-Version:	1.0
From:	Bernhard Loos <bernloos AT web DOT de>
To:	cygwin AT cygwin DOT com
Subject:	Re: dlopen() bug (new testcase)
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com
X-MIME-Autoconverted:	from quoted-printable to 8bit by delorie.com id k2TNa1Q7021804

> -----Ursprüngliche Nachricht-----
> Von: Christopher Faylor
> Gesendet: Wed, 29 Mar 2006 18:15:34 -0500 
>On Thu, Mar 30, 2006 at 01:10:56AM +0200, Bernhard Loos wrote:
>>I looked at the problem again this week, but unfortunately I'm unable
>>to debug anything happening after the first SIGSEGV.  I inserted a view
>>OutputDebugString()-calls and got those results:
>>
>>00:00:00.703: LoadLibraryA("H:\cygwin\test\CrashTest\CrashTest.dll") called from "CYGWIN1.DLL" at address 0x6100FE42 by thread 1.
>>00:00:00.718: Loaded "CRASHTEST.DLL" at address 0x003F0000 by thread 1.  Successfully hooked module.
>>00:00:00.718: DllMain(0x003F0000, DLL_PROCESS_ATTACH, 0x00000000) in "CRASHTEST.DLL" called by thread 1.
>>00:00:00.718: myfault::faulted
>>00:00:00.718: setup_fault
>>00:00:00.718: First chance exception 0xC0000005 (Access Violation) occurred in "CYGWIN1.DLL" at address 0x610B2DE2 by thread 1.
>>00:00:00.718: Unloaded "CRASHTEST.DLL" at address 0x003F0000 by thread 1.
>>00:00:00.718: LoadLibraryA("H:\cygwin\test\CrashTest\CrashTest.dll") returned NULL by thread 1. Error: Unzulssiger Zugriff auf einen Speicherbereich (998).
>>00:00:00.781: First chance exception 0xC0000005 (Access Violation) occurred at address 0x003F101A by thread 1.
>>00:00:00.781: return_from_fault
>>00:00:00.781: First chance exception 0xC0000005 (Access Violation) occurred at address 0x40000060 by thread 1.
>>00:00:00.781: First chance exception 0xC0000029 (Unknown) occurred in "NTDLL.DLL" at address 0x7C95EB28 by thread 1.
>>
>>It looks, like Windows unloads the DLL after the first exception even before the myfault-exception handler is able to catch it.
>>So return_from_fault() tries to longjmp to code wich isn't present any more an the second exception occurs.
>>
>>To fix this problem, I would suggest to use the IsBadReadPtr()-function instead of the myfault-exception handler to check the pointer in 
>>verifyable_object_isvalid().
>>I could write a patch, if nobody has any objections.
>
>Sorry, no.  We *just* got rid of IsBadReadPtr's.

Just out of interest, what's the problem with IsBadReadPtr?
>
>FWIW, I doubt that Windows is really ignoring an exception handler.

The exception handler is called, but at least the return_from_fault is called after the DLL gets unloaded,
as you can see above.

At the moment, cygwin is unable to load any C++-Dll with static classes calling the pthread_key_create
in their constructor. As the standart C++ exception code also calls this function, this happens also, if a
object is created in the constructor.

       Bernhard Loos


PS: Please CC me, I'm not subscribed to the list.
______________________________________________________________
Verschicken Sie romantische, coole und witzige Bilder per SMS!
Jetzt bei WEB.DE FreeMail: http://f.web.de/?mc=021193


--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/

- Raw text -