Hi Hari,

Sorry for not responding to this earlier.   I have seen this problem too.   I will look into it further.   For now, though, it seems to be an off-by-one error of some kind.   An unsatisfying, but pragmatic, workaround is to allocate N+1 header words (where you desire N).

Hopefully I’ll be able you offer a better solution after the holiday break.


From: Hari Krishnan <hkrish4@tigers.lsu.edu>
Reply-To: "General discussion of Jikes RVM design, implementation, issues, and plans" <jikesrvm-researchers@lists.sourceforge.net>
Date: Tuesday, 24 December 2013 1:04 pm
To: "General discussion of Jikes RVM design, implementation, issues, and plans" <jikesrvm-researchers@lists.sourceforge.net>
Subject: Re: [rvm-research] [rvm-core] Regarding Exception thrown in RefCount Implementation.

Hi Erik and Robin, 

Thank you for the reply.  I am using RDB to inspect Boot Image.  I am going to download the earlier stable release now  and will let you know the status soon. 


On Mon, Dec 23, 2013 at 8:21 AM, Erik Brangs <erik.brangs@gmx.de> wrote:

On 19.12.2013 01:45, Hari Krishnan wrote:
> I cannot figure out why this error pops up.

Based on your previous mails, I assume that you've already read the documentation. I'm not proficient in MMTk so I can't give you any specific advice. However, my experience is that it is a good idea to read a book about debugging if you never had any formal education in debugging.

You can also take a look at rdb ( http://sape.inf.usi.ch/rdb ), a Jikes RVM specific debugger that's being developed by Dmitri Makarov and Matthias Hauswirth at the University of Lugano. AFAIK you'll need to use Mac OS if you want to attach to a running Jikes RVM. If you don't use Mac OS, you can still use rdb to examine the bootimage.

> I am attaching the patch here that reproduced that error. The error that produced is following:

I can confirm that the patch reproduces the problem on hg tip for the BaseBaseRefCount configuration. I'm not sure whether it's a MMTk problem or a problem in the interaction of MMTk and Jikes RVM. Perhaps the MMTk test harness can be used to determine that?

Kind regards,

Erik Brangs

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