#15432: Use a callback with a weak reference to WeakValueDictionary
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Reporter: nbruin | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.0
Component: memleak | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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Following http://bugs.python.org/issue417795, we should probably only
reference the dict weakly from the callback object to avoid unnecessary
circular references.
As we found in http://trac.sagemath.org/ticket/15367#comment:39, if an
object C involved in a reference cycle becomes unreachable as a side
effect of circular GC (e.g., a callback somewhere), the object C will only
be collected by GC in the next round. A non-circularly referenced object C
would have its reference count hit 0 and would be collected immediately.
That is already a good reason to try and avoid circular references, even
now that Python does clean them up eventually.
See also http://trac.sagemath.org/ticket/13394#comment:19 (reasoning the
validity of using a strongly referencing closure should be fine in theory
-- this didn't take into account the practical consideration above).
--
Ticket URL: <http://trac.sagemath.org/ticket/15432>
Sage <http://www.sagemath.org>
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