On Feb 24, 2009, at 12:59 AM, Stefan Behnel wrote:
> Robert Bradshaw wrote:
>> On Feb 24, 2009, at 12:38 AM, Stefan Behnel wrote:
>>> http://trac.cython.org/cython_trac/ticket/218
>>
>> Note that the cleanup code is not (and cannot) always be safe across
>> multiple modules. When objects such as interned strings, numerical
>> literals, etc. are released, the module code becomes unsafe to use
>> (e.g. even a __del__ method of an object laying around somewhere
>> else.)
>
> Hmm, we're in a ref-counted environment. Why would these objects be
> released when the module itself is still in use?
That is what the cleanup functions do--they try and release the
memory in use by the module. The problem is that it isn't easy to
tell when a module is still in use (as far as I can tell). It sounds
like things have improved with Py3's unloading of modules.
A concrete example might help explain things. Say I have a Cython class
class A:
def __del__(self):
print 1
Now when this is compiled, a python int 1 will be created and stored
in the module dictionary. If the module defining A is cleaned up
before every instance of A is deallocated, then the cached Python 1
will be collected and then at some later point A.__del__ could be
called, which may result in a segfault.
- Robert
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