__del__ method died with
Fatal Python error: GC object already in linked list
in both release and debug builds. Fixed that. Added a new test that
dies without the fix.
Repair segfaults and infinite loops in COUNT_ALLOCS builds in the
presence of new-style (heap-allocated) classes/types.
Note: test_gc fails in a COUNT_ALLOCS build now, because it expects
a new-style class to get garbage collected.
2.2.1 has another bug that prevents the regression (which isn't a
regression at all) from showing up. "The regression" is actually a
glitch in cyclic gc that's been there forever.
As the generation being collected is analyzed, objects that can't be
collected (because, e.g., we find they're externally referenced, or
are in an unreachable cycle but have a __del__ method) are moved out
of the list of candidates. A tricksy scheme uses negative values of
gc_refs to mark such objects as being moved. However, the exact
negative value set at the start may become "more negative" over time
for objects not in the generation being collected, and the scheme was
checking for an exact match on the negative value originally assigned.
As a result, objects in generations older than the one being collected
could get scanned too, and yanked back into a younger generation. Doing
so doesn't lead to an error, but doesn't do any good, and can burn an
unbounded amount of time doing useless work.
A test case is simple (thanks to Kevin Jacobs for finding it!):
x = []
for i in xrange(200000):
x.append((1,))
Without the patch, this ends up scanning all of x on every gen0 collection,
scans all of x twice on every gen1 collection, and x gets yanked back into
gen1 on every gen0 collection. With the patch, once x gets to gen2, it's
never scanned again until another gen2 collection, and stays in gen2.
Opened another bug about that 2.2.1 isn't actually tracking (at least)
iterators, generators, and bound method objects, due to using the 2.1
gc API internally in those places (which #defines itself out of existence
in 2.2.x).
Add more links to the "See also" section for the xml.sax package.
Talk about interfaces rather than implementation classes where appropriate.
Add hyperlinks to make the documentation on the Attributes and AttributesNS
interfaces more discoverable.
Closes SF bug #484603.
