> Modules dicts are cleared during interpreter shutdown to break such cycles.
That is precisely what's not working because of the cycles, check the first message in the issue: https://bugs.python.org/msg385297 > Also: Why are types mutable ? AFAIK, they are only meant to be mutable at C level and then only until they are fully initialized (PyType_Ready() called). Check https://bugs.python.org/issue43916 On Thu, 27 May 2021 at 19:38, Marc-Andre Lemburg <m...@egenix.com> wrote: > On 27.05.2021 20:20, Pablo Galindo Salgado wrote: > >> And if a type pointer is the only thing being visited, then there's > > no point unless the object can itself be reachable from the type object. > > > > But that could happen easily for heap types as they are mutable by > default. For > > instance, you set the instance in a global: > > > > type -> module -> globals -> instance -> type > > Modules dicts are cleared during interpreter shutdown to break > such cycles. You would not really want to use GC to clear > type objects: if you GC the type object before the instance, > this would create really difficult to handle situations :-) > > Also: Why are types mutable ? AFAIK, they are only meant to be > mutable at C level and then only until they are fully initialized > (PyType_Ready() called). > > > On Thu, 27 May 2021, 19:07 Tim Peters, <tim.pet...@gmail.com > > <mailto:tim.pet...@gmail.com>> wrote: > > > > [Tim Peters <tim.pet...@gmail.com <mailto:tim.pet...@gmail.com>>] > > > ... > > > This is, I believe, akin to what Marc-Andre is bringing up: if X > > > can't be reached _from_ X's type object, there's no need for X's > > > tp_traverse to visit X's type object. It _can_ be visited, but it > > > would be a waste of time. > > > > Ya, I need to retract that :-) If X's type object is in a cycle not > > directly containing X, and X is in a cycle not directly containing > its > > type object, and both cycles are dead, then X's tp_traverse must > visit > > X's type object for cyclic gc to deduce that the cycle directly > > containing the type object _is_ dead. > > > > Else only the cycle containing X will be reclaimed, and the cycle > > containing the type object will have to wait for another gc run. > > > > But that doesn't apply to some of the patches we're seeing. We're > > seeing visits to things that can't possibly be parts of cycles: > > > > +static int > > +pattern_traverse(PatternObject *self, visitproc visit, void *arg) > > +{ > > + Py_VISIT(Py_TYPE(self)); > > + Py_VISIT(self->groupindex); > > + Py_VISIT(self->indexgroup); > > + Py_VISIT(self->pattern); > > + return 0; > > +} > > + > > > > For example, self->pattern there is a string. For that matter, it's > > hard to conceive of how a regexp pattern object could possibly be a > > direct member of any cycle. > > > > And if a type pointer is the only thing being visited, then there's > no > > point unless the object can itself be reachable from the type object. > > > > -- > Marc-Andre Lemburg > eGenix.com > > Professional Python Services directly from the Experts (#1, May 27 2021) > >>> Python Projects, Coaching and Support ... https://www.egenix.com/ > >>> Python Product Development ... https://consulting.egenix.com/ > ________________________________________________________________________ > > ::: We implement business ideas - efficiently in both time and costs ::: > > eGenix.com Software, Skills and Services GmbH Pastor-Loeh-Str.48 > D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg > Registered at Amtsgericht Duesseldorf: HRB 46611 > https://www.egenix.com/company/contact/ > https://www.malemburg.com/ > >
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