[Vm-dev] Debugging VM crash, INVALID RECEIVER / a(n) bad class ??

[Mariano Martinez Peck]

On Mon, Nov 16, 2015 at 1:07 PM, Nicolai Hess <nicolaihess at gmail.com> wrote:

>
> Hi Mariano, if you know the method that may cause this crash can you check
> if it works if you recompile this method with the old compiler,
> maybe this issue is responsible - wrong stack frame size :
> 13854
> <https://pharo.fogbugz.com/f/cases/13854/frameSize-calculated-wrongly-for-lineSegmentsDo>
> frameSize calculated wrongly for #lineSegmentsDo:
>
>
Hi Nicolai,

Thanks for the pointer. I tried with your fix and I still get the same
results (even after recompiling).
However...if I swap back to old Compiler rather than OpalCompiler and I
recompile everything, then I do not have anymore the crash.
So it's definitively something related to Opal compilation, and probably,
related to closures compilation.
I will see if I find other opal issues opened in 4.0.

Thanks!


>
>
> 2015-11-16 17:00 GMT+01:00 Mariano Martinez Peck <marianopeck at gmail.com>:
>
>>
>> Hi guys,
>>
>> I am debugging a Pharo VM crash I am having and I cannot figure out what
>> it is exactly. I suspect it might be related to block closures compilation
>> but I am not sure. I have a reproducible crash test under Pharo 4.0 and
>> OSX.
>>
>> I built a VM in debug mode and I run it via gdb. This is the kind of info
>> I am able to see:
>>
>> *Program received signal SIGSEGV, Segmentation fault.*
>> *0x000ab66b in updatePointersInRangeFromto (memStart=924623948,
>> memEnd=928201420) at
>> /Users/mariano/Pharo/git/pharo-vm/src/vm/gcc3x-cointerp.c:40444*
>> *40444 && (((longAt(fieldOop)) & MarkBit) != 0)) {*
>> *(gdb) call printAllStacks()*
>> *Process 0x30e228c4 priority 40*
>> *0xbffb2e10 M FaAction class>block: 0x20ebb104: a(n) FaAction class*
>> *0xbffb2e30 M BlockClosure(FaMemoryStoreSession)>register: 0x371d0968:
>> a(n) BlockClosure*
>> *0xbffb2e4c M INVALID RECEIVER>register: 0x371cfd54: a(n) bad class*
>>
>> *(callerContextOrNil == (nilObject())) || (isContext(callerContextOrNil))
>> 48626*
>> *0x3721e1f0 is not a context*
>> *0x371c34b4 is not a context*
>>
>> And another crash:
>>
>> *Program received signal SIGSEGV, Segmentation fault.*
>> *0x000ab66b in updatePointersInRangeFromto (memStart=924677864,
>> memEnd=928262300) at
>> /Users/mariano/Pharo/git/pharo-vm/src/vm/gcc3x-cointerp.c:40444*
>> *40444 && (((longAt(fieldOop)) & MarkBit) != 0)) {*
>> *(gdb) call printAllStacks()*
>> *Process 0x30e228c4 priority 40*
>> *0xbffb2de0 M INVALID RECEIVER>initialize 0x3722b9a0: a(n) bad class*
>> *0xbffb2df8 M FaAction class(Behavior)>new 0x20ebb104: a(n) FaAction
>> class*
>> *0xbffb2e10 M FaAction class>block: 0x20ebb104: a(n) FaAction class*
>> *0xbffb2e30 M INVALID RECEIVER>register: 0x371ddee0: a(n) bad class*
>> *0xbffb2e4c M INVALID RECEIVER>register: 0x371dd328 is in old space*
>>
>> *(callerContextOrNil == (nilObject())) || (isContext(callerContextOrNil))
>> 48626*
>> *0x3722b750 is not a context*
>> *[New Thread 0x1b43 of process 5886]*
>> *[New Thread 0x1d2f of process 5886]*
>> *[New Thread 0x1f07 of process 5886]*
>> *[New Thread 0x1e07 of process 5886]*
>>
>> From what I can see in *#printActivationNameFor: aMethod receiver:
>> anObject isBlock: isBlock firstTemporary: maybeMessage*
>> It looks like if the memory address is not an OOP, nor forwarding pointer
>> nor...
>>
>> It also seems like the above stack I can get is not the real cause but a
>> side effect that makes GC to crash (#updatePointersInRangeFromto)
>>
>> As said, I have a way to reproduce the crash, and I already have the VM
>> compiled in debug and gdb running. I can also attach the full output of the
>> gdb stack.
>>
>> BTW.... in the output of the gdb I see lots of printings like:
>>
>> *(numStack + ReceiverIndex) < (lengthOf(theContext)) 45421*
>> *(ReceiverIndex + contextSize) < (lengthOfbaseHeaderformat(oop, header2,
>> fmt)) 40416*
>>
>>
>> Any pointer is appreciated.
>>
>> Thanks!
>>
>> --
>> Mariano
>> http://marianopeck.wordpress.com
>>
>>
>
>


-- 
Mariano
http://marianopeck.wordpress.com
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