I've just added another debugging category to the debug logging code, so now object finalization is reported in the log.

Finalization is a special step taken before freeing those objects which the collector cannot automatically clean up (e.g. because they need to release non-collector-managed resources).

Classes with finalizers include SPDocument and SPDesktop.

Try it out with latest SVN:

INKSCAPE_DEBUG_LOG=debug.xml INKSCAPE_DEBUG_FILTER=REFCOUNT,FINALIZERS src/inkscape

Open some documents, close them, and before closing the last one, go to the "About Memory" dialog and click "recalculate" a few times to make sure that a garbage collection pass gets run.

Then look at debug.xml. You can see not only when the finalization of an object happened, but also what debugging events (in this case refs/unrefs) happened during its finalizer.

-mental