On Monday, December 31, 2012 5:32:05 PM UTC+1, Nils Bruin wrote: > > On Dec 31, 7:29 am, Nils Bruin <nbr...@sfu.ca> wrote: > > > I am not sure that this is exactly the issue we're running into, but > > it seems plausible (it certainly needs a very brittle confluence of > > circumstances to become apparent). Furthermore, I think it is a > > scenario that does need addressing, because TripleDictEraser doesn't > > seem to guard against this. > > In fact, upon further inspection, I don't think this issue is what > bites us here. The dictionary in question only contains weakrefs in > its values. > > I now believe this is a genuine bug in Python. We don't have a good > testcase, though, so I don't know how to report. However, as you see > in the traceback: > > #0 PyObject_Free (p=0x7fffbeb3e330) at Objects/obmalloc.c:981 > #1 0x00007ffff7cc7b76 in subtype_dealloc (self=0x7fffbeb3e350) at > Objects/typeobject.c:1014 > #2 0x00007ffff7d4b7ca in delete_garbage (old=0x7ffff7fe19e0, > collectable=0x7fffffffafb0) at Modules/gcmodule.c:770 > #3 collect (generation=1) at Modules/gcmodule.c:930 > #4 0x00007ffff7d4c1a8 in collect_generations () at Modules/ > gcmodule.c: > 996 > #5 _PyObject_GC_Malloc (basicsize=<optimized out>) at Modules/ > gcmodule.c:1457 > #6 _PyObject_GC_Malloc (basicsize=<optimized out>) at Modules/ > gcmodule.c:1439 > #7 0x00007ffff7d4c1cd in _PyObject_GC_New (tp=0x7ffff7fb7d00) at > Modules/gcmodule.c:1467 > #8 0x00007ffff7c86cb8 in PyWrapper_New (d=0x7ffff7bce230, > self=0xb2eca0) at Objects/descrobject.c:1068 > > (this is below the TripleDictEraser call). What you see is that during > our callback, a garbage collection is triggered! This of course > discovers all sorts of things that can be deleted, including things > that are already scheduled for deletion. Other interpretations would > be very welcome. > It seems very plausible, whence the possible need to look at Py_Clear.
The difference between the "del A[1]" and "A.__delitem__(1)" might only be the fact that in the latter case (where more fucntions calls are performed) a gc is triggered whereas its not in the first case, that's just a wild guess though. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To post to this group, send email to sage-devel@googlegroups.com. To unsubscribe from this group, send email to sage-devel+unsubscr...@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel?hl=en.
