From 412c3ac4f1cfe361868f35a78b3b02ad03a0a518 Mon Sep 17 00:00:00 2001 From: Tim Peters Date: Mon, 1 Dec 2003 22:13:12 +0000 Subject: Py_Finalize(): disabled the second call of cyclic gc, and added extensive comments about why both calls to cyclic gc here can cause problems. Already fixed on the trunk. Since the calls were introduced in 2.3, that's the end of it. --- Misc/NEWS | 10 ++++++++++ Python/pythonrun.c | 29 +++++++++++++++++++++++++++-- 2 files changed, 37 insertions(+), 2 deletions(-) diff --git a/Misc/NEWS b/Misc/NEWS index e0d5c84..7731c7a 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -33,6 +33,16 @@ Core and builtins in a debug build, a segfault occurred reliably very soon after). This has been repaired. +- At Python shutdown time (Py_Finalize()), 2.3 called cyclic garbage + collection twice, both before and after tearing down modules. The + call after tearing down modules has been disabled, because too much + of Python has been torn down then for __del__ methods and weakref + callbacks to execute sanely. The most common symptom was a sequence + of uninformative messages on stderr when Python shut down, produced + by threads trying to raise exceptions, but unable to report the nature + of their problems because too much of the sys module had already been + destroyed. + - Patch #820195: object.__contains__() now returns True or False instead of 1 or 0. diff --git a/Python/pythonrun.c b/Python/pythonrun.c index d32c376..715c464 100644 --- a/Python/pythonrun.c +++ b/Python/pythonrun.c @@ -332,15 +332,40 @@ Py_Finalize(void) warnings_module = NULL; /* Collect garbage. This may call finalizers; it's nice to call these - before all modules are destroyed. */ + * before all modules are destroyed. + * XXX If a __del__ or weakref callback is triggered here, and tries to + * XXX import a module, bad things can happen, because Python no + * XXX longer believes it's initialized. + * XXX Fatal Python error: Interpreter not initialized (version mismatch?) + * XXX is easy to provoke that way. I've also seen, e.g., + * XXX Exception exceptions.ImportError: 'No module named sha' + * XXX in ignored + * XXX but I'm unclear on exactly how that one happens. In any case, + * XXX I haven't seen a real-life report of either of these. + */ PyGC_Collect(); /* Destroy all modules */ PyImport_Cleanup(); /* Collect final garbage. This disposes of cycles created by - new-style class definitions, for example. */ + * new-style class definitions, for example. + * XXX This is disabled because it caused too many problems. If + * XXX a __del__ or weakref callback triggers here, Python code has + * XXX a hard time running, because even the sys module has been + * XXX cleared out (sys.stdout is gone, sys.excepthook is gone, etc). + * XXX One symptom is a sequence of information-free messages + * XXX coming from threads (if a __del__ or callback is invoked, + * XXX other threads can execute too, and any exception they encounter + * XXX triggers a comedy of errors as subsystem after subsystem + * XXX fails to find what it *expects* to find in sys to help report + * XXX the exception and consequent unexpected failures). I've also + * XXX seen segfaults then, after adding print statements to the + * XXX Python code getting called. + */ +#if 0 PyGC_Collect(); +#endif /* Destroy the database used by _PyImport_{Fixup,Find}Extension */ _PyImport_Fini(); -- cgit v0.12