[vbox-dev] "An invalid or unaligned stack was encountered during an unwind operation" in VBoxREM.dll

[Rūdolfs Bundulis]

Hi Klaus,

thanks for the explanations, I'll try running the software under gdb to get
more info - most likely it is my fault, simply with the current information
from Visual Studio I've got zero hints. Thanks.

2014-10-28 12:39 GMT+02:00 Klaus Espenlaub <klaus.espenlaub at oracle.com>:

> Rūdolfs,
>
> On 27.10.2014 22:39, Rūdolfs Bundulis wrote:
> > Hi,
> >
> > my custom frontend for VirtualBox seemed to work fine and stable but
> > then I started to play around with number of CPU's and memory and I
> > started getting "An invalid or unaligned stack was encountered during an
> > unwind operation" from VBoxREM.dll. I downloaded the sources for
> > VirtualBox 4.3.18, built it for x64 debug and started debugging.
> >
> > * The first weird thing was that I could not find a .pdb file for
> > VBoxREM.dll, is that some kind of special .dll? I have pdb files for
> > VBoxC.dll and friends under "out\win.amd64\debug\stage\debug\bin" but I
> > can't find one for VBoxREM.dll.
>
> That's expected... VBoxREM.dll is very special, it contains the (qemu)
> recompiler, which must be built using gcc, and that's the reason why
> there are no pdb files for it. It should contain dwarf debug info
> straight in the dll, which gdb understands. Yes, it's annoying because
> one has to pick the right debugger straight from the beginning.
>
> > * The stack trace is (I know it won't give much help):
> >
> > ntdll.dll!00007ffe679ac0b4()Unknown
> > ntdll.dll!00007ffe67913356()Unknown
> > msvcrt.dll!__longjmp_internal ()Unknown
> >  >VBoxREM.dll!000000006fb0f3c4()Unknown
> >
> > The frontend does not have any output from VirtualBox on stdout or
> > stderr and the logfile also does not show any errors.
> >
> > Could anyone provide any pointers how should I approach debugging this?
>
> Hope gdb is helpful.
>
> On modern hardware which supports VT-x/AMD-V it's somewhat unexpected
> that you end up in the recompiler, but there are some corner cases which
> it is still used for.
>
> Klaus
>
> >
> > Best Regards,
> > Rudolfs Bundulis
>
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