[Vm-dev] re: debugging the garbage collector

Craig Latta craig at netjam.org
Fri Feb 15 10:07:40 UTC 2013


Hi--

     Noah writes:

> Can anyone give me any pointers to documentation or personal
> experience regarding debugging the object memory and GC?

     Glad you're in the thick of it! :)

     The only debugging like that I've had to do was prompted by trouble
in the object memory, not the virtual machine, so I've been able to get
by with evaluating Interpreter>>allAccessibleObjectsOkay and the like,
at the Smalltalk level at strategic moments. Things like
ObjectMemory>>validateRoots, which can be translated to C and enabled
(by turning on DoAssertionChecks) may help in C-debugger-land.

     I was lucky in past host platform bringups that the GC worked
without modification, from those who came before me on other platforms.
What this usually means is that the new platform's C environment is
sufficiently similar to the other ones. I strongly suspect this will
come down to some C compiler flag or preprocessor whim (hence projects
which try to get rid of the C compilation part from bootstrapping
completely).

     David writes:

> I'm assuming that your VM is derived from a relatively recent
> interpreter VM code base, maybe Craig can confirm?

     The current release of Spoon is 3 beta 3 (23 October 2012),
available at:

     http://netjam.org/spoon/releases/current

     It includes a Squeak 4.2 object memory (4 February 2011) with
VMMaker dtl.237 (23 May 2011) installed, and the Spoon VM changes
applied to that, and with remote browsing support installed. It runs on
the VM it generates, which is the only one supplied in the release (Mac
OS, Linux and win32).


     thanks again,

-C

--
Craig Latta
www.netjam.org/resume
+31   6 2757 7177 (SMS ok)
+ 1 415	 287 3547 (no SMS)



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