Python 3.5.1 C API, the global available available is not destroyed when delete the module

[dl l]

Hi Steven,

Thanks for reply.

I logged bug https://bugs.python.org/issue28202. I added more info in this
bug :).

Yes, it's a workaround to set the global variables to None. But My app just
provide a framework for my customers to run python scripts. That's means
the workaround requires my customers to update their python scripts. That
may make them unhappy :(. Is there a workaround in my code C++ side to call
Python C APIs to resolve the memory leak issue?

2016-09-20 13:49 GMT+08:00 Steven D'Aprano <
steve+comp.lang.python at pearwood.info>:

> On Monday 19 September 2016 16:47, dl l wrote:
>
> > Hi,
> >
> > I have a app loading python35.dll. Use python API PyImport_AddModule
> > to run a py file. And use PyDict_DelItemString to delete the module.
> > There is a global vailable in the py file. The global variable is not
> > destroyed when calling PyDict_DelItemString to delete the module. That
> > cause the memory leak.
>
> See:
>
> https://bugs.python.org/issue28202
>
> > But it is ok with python33.dll, the global variable can be destroyed
> > when calling PyDict_DelItemString to delete the module.
>
> You are calling PyDict_DelItemString on sys.modules, but that won't clear
> the
> reference to the module if there are any other references to it.
>
>
> > How to resolve the problem? Is there a workaround? I need to use
> > python35.dll and wish the global variable in a module can be released
> > automatically when call PyDict_DelItemString to delete the module.
>
> The global object will not be released so long as any other object refers
> to
> it. If the global object is still alive, it will keep the module alive.
>
> Are you sure that the object has no other references to it? Have you put
> it in
> a list or dict or some other object?
>
>
> > Here is the python test code:
> >
> > class Simple:
> >      def __init__( self ):
> >          print('Simple__init__')
> >      def __del__( self ):
> >          print('Simple__del__')
> >
> > simple = Simple()
>
>
> You cannot rely on the __del__ method running at any specific time. It
> might
> not run until your application exists.
>
>
> That test code is not sufficient. How do you call the test code? If you do
> this
> from main:
>
>
> import mymodule  # module above
> del sys.modules['mymodule']
>
>
>
> that will delete the sys.modules cache entry, but the module object is
> still
> alive. If you are absolutely sure there are no other references to the
> global
> variable and the module, then it sounds like a leak.
>
> Can you confirm that the gc is enabled?
>
>
> For a work-around, I can only suggest manually killing the global. What
> happens
> if you do this:
>
> del sys.modules['mymodule']
> mymodule.simple = None
> del mymodule
>
>
> or equivalent?
>
>
>
>
>
> --
> Steven
> git gets easier once you get the basic idea that branches are homeomorphic
> endofunctors mapping submanifolds of a Hilbert space.
>
> --
> https://mail.python.org/mailman/listinfo/python-list
>