[Python-Dev] Re: [PythonLabs] Re: [Python-checkins]python/dist/src/Modules gcmodule.c,2.33.6.5,2.33.6.6 (original) (raw)

Tim Peters tim.one@comcast.net
Sat, 05 Apr 2003 19:05:21 -0500

[Jeremy Hylton]

We've got the first version of boom nailed, but we've got the same problem in handlefinalizers(). The version of boom below doesn't blow up until the second time the hasfinalizer() is called.

It isn't really necessary to call has_finalizer() a second time, and I'll check in changes so that it doesn't anymore (assuming the test suite passes -- it's running as I type this).

I don't understand the logic in handlefinalizers(), though. If the objects are all in the finalizers list, why do we call hasfinalizer() a second time? Shouldn't everything has a finalizer at that point?

I tried to explain that last night. The essence of the changes I have pending is to make move_finalizer_reachable() move the tentatively unreachable objects reachable only from finalizers into a new & distinct list, reachable_from_finalizers. After that, everything in finalizers has a finalizer and nothing in reachable_from_finalizers does, so we don't have to call has_finalizer() again. Before, finalizers contained everything in both (finalizers and reachable_from_finalizers) lists, so another has_finalizer() call on each object was needed to distinguish the two kinds (has a finalizer, doesn't have a finalizer) of objects again.

import gc

class C: def init(self): self.x = 0 def delete(self): print "never called" def getattr(self, attr): self.x += 1 print self.x if self.x > 1: del self.attr else: return self.delete raise AttributeError a = C() b = C() a.attr = b b.attr = a del a, b print gc.collect()

I also added a non-printing variant of this to test_gc. In the new world, the "del self.attr" bits never get called, so this is just a vanilla trash cycle now.