On 1/19/07, M.-A. Lemburg <[EMAIL PROTECTED]> wrote: > On 2007-01-18 20:53, Brett Cannon wrote: > > I have discovered an issue relating to func_globals for functions and > > the deallocation of the module it is contained within. Let's say you > > store a reference to the function encodings.search_function from the > > 'encodings' module (this came up in C code, but I don't see why it > > couldn't happen in Python code). Then you delete the one reference to > > the module that is stored in sys.modules, leading to its deallocation. > > That triggers the setting of None to every value in > > encodings.__dict__. > > > > Oops, now the global namespace for that module has everything valued > > at None. The dict doesn't get deallocated since a reference is held > > by encodings.search_function.func_globals and there is still a > > reference to that (technically held in the interpreter's > > codec_search_path field). So the function can still execute, but > > throws exceptions like AttributeError because a module variable that > > once held a dict now has None and thus doesn't have the 'get' method. > > That's a typical error situation you get in __del__ methods at > the time the interpreter is shut down. >
Yeah, but in this case this is at the end of Py_Initialize() for the stuff I am doing to the interpreter. =) > The main reason for setting everything to None first is to > break circular references and make sure that at least some > of the object destructors can run. > I know the reason, it just happens to occur at a bad time for me. > > My question is whether this is at all worth trying to rectify. Since > > Google didn't turn anything up I am going to guess this is not exactly > > a common thing. =) That would lead me to believe some (probably > > most) of you will say, "just leave it alone and work around it". > > If you can come up with a better way, sure :-) > > > The other option I can think of is to store a reference to the module > > instead of just to its __dict__ in the function. The problem with > > that is we end up with a circular dependency of the functions in > > modules having a reference to the module but then the module having a > > reference to the functions. I tried not having the values in the > > module's __dict__ set to None if the reference count was above 1 and > > that solved this issue, but that leads to dangling references on > > anything in that dict that does not have a reference stored away > > somewhere else like encodings.search_function. > > > > Anybody have any ideas on how to deal with this short of rewriting > > some codecs stuff so that they don't depend on global state in the > > module or just telling me to just live with it? > > I'm not exactly sure which global state you are referring to. The > aliase map, the cache used by the search function ? > encodings._cache . > Note that the search function registry is a global managed > in the thread state (it's not stored in any module). > Right, but that is not the issue. If you have deleted the reference to the encodings module from sys.modules it then sets encodings._cache to None. After the deletion, if you try to encode/decode a unicode string you can an AttributeError about how encodings._cache does not have a 'get' method since it is now None instead of a dict. The function is fine and still runs, it's just that the global state it depends on is no longer the way it assume it should be. -Brett > -- > Marc-Andre Lemburg > eGenix.com > > Professional Python Services directly from the Source (#1, Jan 19 2007) > >>> Python/Zope Consulting and Support ... http://www.egenix.com/ > >>> mxODBC.Zope.Database.Adapter ... http://zope.egenix.com/ > >>> mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/ > ________________________________________________________________________ > > ::: Try mxODBC.Zope.DA for Windows,Linux,Solaris,FreeBSD for free ! :::: > _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
