id,summary,reporter,owner,description,type,status,priority,milestone,component,resolution,keywords,cc,work_issues,upstream,reviewer,author,merged,dependencies,stopgaps
12357,Make groupoids garbage collectable,SimonKing,rlm,"Currently, the groupoid of an object P can not be garbage collected, even when deleting P.

Even worse: The persistence of `Groupoid(P)` also prevents P from being garbage collected.

The attached patch aims at solving it: An external reference to either P or `Groupoid(P)` is enough to keep both alive. But without an external reference, both P and `Groupoid(P)` become collectable.

Example from the docs:
{{{
            sage: P = GF(151)['x','y']
            sage: n = id(Groupoid(P))
            sage: import gc
            sage: _ = gc.collect()
            sage: n == id(Groupoid(P))   # indirect doctest
            True

        Thus, the groupoid is cached. But when deleting ``P``, its
        groupoid can be garbage collected as well::

            sage: del P
            sage: _ = gc.collect()
            sage: P = GF(151)['x','y']
            sage: n == id(Groupoid(P))
            False

        TESTS:

        We test against some corner cases::

            sage: Groupoid(None)
            Traceback (most recent call last):
            ...
            TypeError: Groupoid of None is not defined
            sage: Groupoid(1)
            Traceback (most recent call last):
            ...
            TypeError: 1 must either allow attribute assignment or be instances of <type 'sage.structure.parent.Parent'>
            sage: class A: pass
            sage: a = A()
            sage: Groupoid(a)
            Groupoid with underlying set <__main__.A instance at ...>
            sage: Groupoid(a) is Groupoid(a)
            True
}}}

Superseded by #12313.",defect,closed,major,sage-duplicate/invalid/wontfix,memleak,duplicate,groupoid cache Cernay2012,nthiery jpflori,,N/A,"Simon King, Jean-Pierre Flori",,,"#715, #11521, #12313, #11943",