#10963: More functorial constructions
-------------------------------------+-------------------------------------
Reporter: nthiery | Owner: stumpc5
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.13
Component: categories | Resolution:
Keywords: | Merged in:
Authors: Nicolas M. Thiéry | Reviewers: Simon King, Frédéric
Report Upstream: N/A | Chapoton
Branch: | Work issues:
Dependencies: #11224, #8327, | Commit:
#10193, #12895, #14516, #14722, | Stopgaps:
#13589, #14471, #15069, #15094, |
#11688, #13394 |
-------------------------------------+-------------------------------------
Comment (by nbruin):
There is a way to "borrow" the trashcan: make sure that some standard
python
container type is involved in the chain of deletions. For
`sage.misc.weak_dict`
this can be done by modifying `del_dictitem_by_exact_value` to return the
key
(so it's more "pop_dictitem") and then in the callback do:
{{{
...
v=(del_dictitem_by_exact_value(<PyDictObject *>cself,
<PyObject *>r, r.key),)
del v
...
}}}
i.e., delete a tuple containing the key rather than the key by itself. The
tuple
deallocation routine does participate in the trashcan. Drawbacks:
- this is a little slower
- we're doing a memory allocation (creation of a tuple) in a weakref
callback.
That's not particularly forbidden, but it can trigger a GC.
We could do something similar in `MonoDictEraser` etc. to properly solve
#15069.
Again, the real solution is for cython to participate in the trashcan.
--
Ticket URL: <http://trac.sagemath.org/ticket/10963#comment:166>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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