On 2013-02-13, at 19:48 , Maciej Fijalkowski wrote:
Hi
I've tried (and failed) to find what GC details (especially finalizer semantics) are CPython only and which ones are not. The best I could find was the documentation of __del__ here: http://docs.python.org/2/reference/datamodel.html
Things were pypy differs:
* finalizers in pypy will be called only once, even if the object is resurrected. I'm not sure if this is detail or we're just plain incompatible.
* pypy breaks cycles and runs finalizers in random order (but topologically correct), hence gc.garbage is always empty. I *think* this part is really just an implementation detail
* we're discussing right now about running multiple finalizers. We want to run them in order, but if there is a link a -> b and a becomes unreachable, we want to reserve the right to call finalizer a then finalizer b, even if a.__del__ resurrects a. What do you think?
Overall, the __del__ is baaad.
Cheers, fijal
There may be one more, although I'm not sure whether it's a GC artifact or something completely unspecified: if a context manager is part of a suspended stack (because it's in a generator) when the program terminates, cpython will run __exit__ but pypy will not -- # -*- encoding: utf-8 -*- class C(object): def __enter__(self): print ("entering") def __exit__(self, *args): print ("exiting") def gen(): with C(): yield r = gen() next(r) -- $ python2 test.py entering exiting $ python3 test.py entering exiting $ pypy test.py entering $ --