Sorry, the last link should have been: https://bugs.python.org/issue43908
On Thu, 27 May 2021 at 19:41, Pablo Galindo Salgado <pablog...@gmail.com> wrote: > > 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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