New submission from Neil Schemenauer <nas-pyt...@arctrix.com>:
This is a WIP/proof-of-concept of doing away with Py_TRASHCAN_BEGIN and Py_TRASHCAN_END and instead integrating the functionality into _Py_Dealloc. There are a few advantages: - all container objects have the risk of overflowing the C stack if a long reference chain of them is created and then deallocated. So, to be safe, the tp_dealloc methods for those objects should be protected from overflowing the stack. - the Py_TRASHCAN_BEGIN and Py_TRASHCAN_END macros are hard to understand and a bit hard to use correctly. Making the mechanism internal avoids confusion. The code can be slightly simplified as well. This proof-of-concept seems to pass tests but it will need some careful review. The exact rules related to calling GC Track/Untrack are subtle and this changes things a bit. I.e. tp_dealloc is called with GC objects already untracked. For 3rd party extensions, they are calling PyObject_GC_UnTrack() and so I believe they should still work. The fact that PyObject_CallFinalizerFromDealloc() wants GC objects to definitely be tracked is a bit of a mystery to me (there is an assert to check that). I changed the code to track objects if they are not already tracked but I'm not sure that's correct. There could be a performance hit, due to the _PyType_IS_GC() test that was added to the _Py_Dealloc() function. For non-GC objects, that's going to be a new branch and I'm worried it might hurt a bit. OTOH, maybe it's just in the noise. Profiling will need to be done. ---------- components: Interpreter Core messages: 399433 nosy: nascheme priority: normal severity: normal stage: patch review status: open title: Integrate trashcan mechanism into _Py_Dealloc type: enhancement _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue44897> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
