[Python-Dev] crash in dict on gc collect

[Neal Norwitz]

I wonder if this is similar to Kevin's problem?  I couldn't reproduce
his problem though.  This happens with both debug and release builds.
Not sure how to reduce the test case.  pychecker was just iterating
through the byte codes.  It wasn't doing anything particularly
interesting.

./python pychecker/pychecker/checker.py Lib/encodings/cp1140.py

0x00000000004cfa18 in visit_decref (op=0x661180, data=0x0) at gcmodule.c:270
270             if (PyObject_IS_GC(op)) {
(gdb) bt
#0  0x00000000004cfa18 in visit_decref (op=0x661180, data=0x0) at gcmodule.c:270
#1  0x00000000004474ab in dict_traverse (op=0x7cdd90,  visit=0x4cf9e0
<visit_decref>, arg=0x0) at dictobject.c:1819
#2  0x00000000004cfaf0 in subtract_refs (containers=0x670240) at gcmodule.c:295
#3  0x00000000004d07fd in collect (generation=0) at gcmodule.c:790
#4  0x00000000004d0ad1 in collect_generations () at gcmodule.c:897
#5  0x00000000004d1505 in _PyObject_GC_Malloc (basicsize=56) at gcmodule.c:1332
#6  0x00000000004d1542 in _PyObject_GC_New (tp=0x64f4a0) at gcmodule.c:1342
#7  0x000000000041d992 in PyInstance_NewRaw (klass=0x2a95dffcc0,
dict=0x800e80) at classobject.c:505
#8  0x000000000041dab8 in PyInstance_New (klass=0x2a95dffcc0,
arg=0x2a95f5f9e0, kw=0x0) at classobject.c:525
#9  0x000000000041aa4e in PyObject_Call (func=0x2a95dffcc0,
arg=0x2a95f5f9e0,  kw=0x0) at abstract.c:1802
#10 0x000000000049ecd2 in do_call (func=0x2a95dffcc0,
pp_stack=0x7fbfffb5b0,  na=3, nk=0) at ceval.c:3785
#11 0x000000000049e46f in call_function (pp_stack=0x7fbfffb5b0,
oparg=3) at ceval.c:3597