# Program received signal SIGSEGV, Segmentation fault.
# 0x080f2c17 in PyObject_GetAttr (v=<unknown at remote 0x40573d8c>, name='match') at Objects/object.c:872
# 872         if (tp->tp_getattro != NULL)
# (gdb) bt
# #0  0x080f2c17 in PyObject_GetAttr (v=<unknown at remote 0x40573d8c>, name='match') at Objects/object.c:872
# #1  0x080f2b42 in _PyObject_GetAttrId (v=<unknown at remote 0x40573d8c>, name=0x8328354 <PyId_match.9432>) at Objects/object.c:835
# #2  0x0809c3a6 in _PyObject_CallMethodId (o=<unknown at remote 0x40573d8c>, name=0x8328354 <PyId_match.9432>, format=0x829552c "O")
#     at Objects/abstract.c:2215
# #3  0x0817e48b in check_matched (obj=<unknown at remote 0x40573d8c>, arg='c') at Python/_warnings.c:28
# #4  0x0817e88b in get_filter (category=<type at remote 0x830bf80>, text='', lineno=4, module='c', item=0xbfa87c88)
# (gdb) frame 4
# #4  0x0817e88b in get_filter (category=<type at remote 0x830bf80>, text='', lineno=4, module='c', item=0xbfa87c88)
#     at Python/_warnings.c:152
# 152             good_mod = check_matched(mod, module);
# (gdb) print *mod
# $1 = {_ob_next = 0xdbdbdbdb, _ob_prev = 0xdbdbdbdb, ob_refcnt = -606348325, ob_type = 0xdbdbdbdb}
# 
# "mod" object is deleted in "match" method. Use after free.
# 

import warnings as w

class X:
  def match(self, a):
    global L

    print("match")
    L[:] = []

  def __del__(self):
    print("__del__")

L = [(X(),X(),X(),X(),0) for i in range(2)]
w.filters = L
w.warn_explicit(Warning(),"b","c",4)