[Vm-dev] Re: FFI crashes VM on Linux (was: Z3950 on OSX: module yaz3 not found)

[David T. Lewis]

On Fri, Dec 24, 2010 at 12:44:50PM -0300, Hern??n Morales Durand wrote:
> 
> Hi David,
> 
> 2010/12/24 David T. Lewis <lewis at mail.msen.com>:
> >
> > Hern??n,
> >
> > A segmentation fault that occurs when calling the function in an
> > external library would most likely indicate that the arguments being
> > passed to the library function are not correct for some reason.
> > Probably it is something related to the ExternalStructure as you
> > mention.
> 
> The strange thing is that in the Windows VM goes fine.

There are differences in the Windows an unix implementations, so
sometimes a declaration that works on Windows may need to be done
differently on unix. I don't have any examples, but I know I have
seen this in the past.

> Is there a
> special VM debug flag or parameter specifically for this cases? Maybe
> I could check with that.

I do not know of anything that would help here. In the past I have
done debugging by setting gdb breakpoints right before running
the workspace script. It's a real pain but it can be done.

I know that this does not answer your question, but if you can
consider building a plugin rather than using FFI, I think you may
find it to be easier to debug and more reliable overall.

Dave

> 
> > You must use a normal 32-bit VM and 32-bit libraries. I think that
> > you are doing this, but I mention it because using 64-bit VM or
> > libraries will definitely crash FFI.
> > ??<http://bugs.squeak.org/view.php?id=7237>
> >
> 
> Yes, I'm sure because Ubuntu 8.10 doesn't allow to install libraries
> compiled for another architecture.
> 
> Cheers,
> 
> > Dave
> >
> > On Fri, Dec 24, 2010 at 08:33:33AM +0100, laurent laffont wrote:
> >>
> >> Which VM have you used ?
> >>
> >> I cross post to vm-dev list.
> >>
> >> Laurent.
> >>
> >> On Fri, Dec 24, 2010 at 3:54 AM, Hern??n Morales Durand <
> >> hernan.morales at gmail.com> wrote:
> >>
> >> > Laurent, not much progress here :(
> >> > I just reproduced the Unix VM crash. First I've linked the library so
> >> > we do not have to change every module name call
> >> >
> >> > user at ubuntu:/usr/lib$ ln -T -s /usr/lib/libyaz.so.3.0.0 yaz
> >> >
> >> > and I've tried to execute the library tracer in the shell script
> >> >
> >> > ltrace -f -l /usr/lib/libyaz.so.3.0.0 -o out.txt "$BASE/squeakvm" \
> >> > ?? ?? ?? ??-plugins "$BASE" \
> >> > ?? ?? ?? ??-encoding latin1 \
> >> > ?? ?? ?? ??-vm-display-X11 \
> >> > ?? ?? ?? ??"$ROOT/Contents/Resources/pharo.image"
> >> >
> >> > but it crash the VM too with an unhandled exception even before the
> >> > GUI is displayed.
> >> > What I've observed is that every FFI call which receives an
> >> > ExternalStructure as parameter kills the VM. This is weird because
> >> > this doesn't happen in the Windows VM. I ran this little script I use
> >> > to debug the library
> >> >
> >> > | conn lib rs rsSize records |
> >> > lib := Z3950FFILibrary default.
> >> > conn := lib
> >> > ?? ?? ?? ??createConnectionTo: #Alabama asZ3950Server hostName
> >> > ?? ?? ?? ??port: 7090.
> >> > lib createOptions.
> >> > lib
> >> > ?? ?? ?? ??setConnection: conn
> >> > ?? ?? ?? ??optionName: 'preferredRecordSyntax'
> >> > ?? ?? ?? ??optionValue: 'USMARC'.
> >> > rs := lib
> >> > ?? ?? ?? ??searchPqf: conn
> >> > ?? ?? ?? ??query: ??'@attr 1=1003 collins'.
> >> > rsSize := lib resultSetSize: rs.
> >> > rsSize > 0
> >> > ?? ?? ?? ??ifFalse: ??[ 'no results' ].
> >> > records := Array new: rsSize.
> >> > 0 to: rsSize - 1 do: [: pos |
> >> > ?? ?? ?? ??record := lib resultSetRecord: rs position: pos.
> >> > ?? ?? ?? ??record isNil not
> >> > ?? ?? ?? ?? ?? ?? ?? ??ifTrue: ??[
> >> > ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??records
> >> > ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??at: pos + 1
> >> > ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??put: ( lib
> >> > ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??getRecord: record
> >> > ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??function: 'render; charset=marc8,
> >> > iso8859-1'
> >> > ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??length: nil ). ] ].
> >> > records
> >> >
> >> > and the the doIt just hangs the VM, the console output going through
> >> > the Debugger is the following:
> >> >
> >> > Segmentation fault
> >> >
> >> > -1370902312 ContextPart>doPrimitive:method:receiver:args:
> >> > -1370902404 ContextPart>tryPrimitiveFor:receiver:args:
> >> > -1370902788 ContextPart>send:to:with:super:
> >> > -1370902896 ContextPart>send:super:numArgs:
> >> > -1370902988 InstructionStream>interpretExtension:in:for:
> >> > -1370903080 InstructionStream>interpretNextInstructionFor:
> >
> >
> 
> 
> 
> -- 
> Hern??n Morales
> Information Technology Manager,
> Institute of Veterinary Genetics.
> National Scientific and Technical Research Council (CONICET).
> La Plata (1900), Buenos Aires, Argentina.
> Telephone: +54 (0221) 421-1799.
> Internal: 422
> Fax: 425-7980 or 421-1799.