diff --git a/Misc/NEWS b/Misc/NEWS index 2d323eabcb5..7bc9817f1be 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -294,6 +294,14 @@ Tools/Demos Build +- A bug was fixed that could cause COUNT_ALLOCS builds to segfault, or + get into infinite loops, when a new-style class got garbage-collected. + Unfortunately, to avoid this, the way COUNT_ALLOCS works requires + that new-style classes be immortal in COUNT_ALLOCS builds. Note that + COUNT_ALLOCS is not enabled by default, in either release or debug + builds, and that new-style classes are immortal only in COUNT_ALLOCS + builds. + - Compiling out the cyclic garbage collector is no longer an option. The old symbol WITH_CYCLE_GC is now ignored, and Python.h arranges that it's always defined (for the benefit of any extension modules diff --git a/Objects/object.c b/Objects/object.c index 5c5390849ff..fd069f1fe63 100644 --- a/Objects/object.c +++ b/Objects/object.c @@ -74,6 +74,15 @@ inc_count(PyTypeObject *tp) if (tp->tp_next != NULL) /* sanity check */ Py_FatalError("XXX inc_count sanity check"); tp->tp_next = type_list; + /* Note that as of Python 2.2, heap-allocated type objects + * can go away, but this code requires that they stay alive + * until program exit. That's why we're careful with + * refcounts here. type_list gets a new reference to tp, + * while ownership of the reference type_list used to hold + * (if any) was transferred to tp->tp_next in the line above. + * tp is thus effectively immortal after this. + */ + Py_INCREF(tp); type_list = tp; } tp->tp_allocs++;