On Fri, 11 Feb 2011, Ozkan Sezer wrote:
On Fri, Feb 11, 2011 at 11:35 AM, Kai Tietz <[email protected]> wrote:
2011/2/11 Joel Dice <[email protected]>:
Hi all,
My application uses AddVectoredExceptionHandler to register an exception
handler which, if it can't handle the exception, tries to create a mini
dump file for later analysis. This involves using MiniDumpWriteDump from
dbghelp.dll, which accepts a pointer to a MINIDUMP_EXCEPTION_INFORMATION
instance which wraps the LPEXCEPTION_POINTERS instance provided to the
exception handler by the OS.
All this works great on 32-bit systems, but crashes on 64-bit ones. To
find out why, I ran my app in WinDbg and found that code in
MiniDumpWriteDump was triggering an EXCEPTION_ACCESS_VIOLATION. Tracing
through the disassembled code revealed that MiniDumpWriteDump is looking
for the ExceptionPointers field at a four byte offset from the beginning
of the MINIDUMP_EXCEPTION_INFORMATION instance I passed as a parameter.
However, the natural alignment of that field is 8 bytes, so GCC added
padding after the first field (ThreadId) to achieve that alignment.
Once I realized what was happening, I defined my own version of
MINIDUMP_EXCEPTION_INFORMATION with __attribute__ ((__packed__)) to
eliminate the padding, and this fixed the crash.
Should MINIDUMP_EXCEPTION_INFORMATION be declared with __attribute__
((__packed__)) in dbghelp.h? Are there other structures in that header
that should be similarly declared?
Thanks.
Joel,
thanks for the report. Feel free to provide a patch for this
adjustment. Nevertheless I am a bit curious, as those structures in
dbghelp.h have a packing of 4 bytes (see pshpack4.h).
Maybe we should see how the header is included along
with some other defines etc. in the relevant source ?
That was good advice, since it made me notice that the problem was
entirely on my end to begin with. The version of MingGW32 I was using
before I switched to MinGW-W64 did not have dbghelp.h at all, so I had
been declaring all the structures I needed myself based on the MSDN
documentation. I had totally forgotten about that until I took a closer
look at my source code.
Anyway, I've switched over to using MinGW-W64's dbghelp.h and it's working
perfectly. Thanks for your help, and sorry for the noise.
Thanks also for all the good work put into this project; it's very much
appreciated.
Thanks,
Kai
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