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.
FWIW, I doubt that Windows is really ignoring an exception handler.
cgf
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