New submission from Fish Wang :
I come across this issue recently when developing a multi-threaded PySide2 (Qt)
application. When I'm calling .copy() on a WeakValueDictionary, there is a high
chance that my application crashes with the following stack backtrace:
--
Traceback (most recent call last):
File "F:\angr\angr-management\angrmanagement\ui\widgets\qdisasm_graph.py",
line 239, in mouseDoubleClickEvent
block.on_mouse_doubleclicked(event.button(),
self._to_graph_pos(event.pos()))
File "F:\angr\angr-management\angrmanagement\ui\widgets\qblock.py", line 130,
in on_mouse_doubleclicked
obj.on_mouse_doubleclicked(button, pos)
File "F:\angr\angr-management\angrmanagement\ui\widgets\qinstruction.py",
line 128, in on_mouse_doubleclicked
op.on_mouse_doubleclicked(button, pos)
File "F:\angr\angr-management\angrmanagement\ui\widgets\qoperand.py", line
162, in on_mouse_doubleclicked
self.disasm_view.jump_to(self._branch_target, src_ins_addr=self.insn.addr)
File "F:\angr\angr-management\angrmanagement\ui\views\disassembly_view.py",
line 258, in jump_to
self._jump_to(addr)
File "F:\angr\angr-management\angrmanagement\ui\views\disassembly_view.py",
line 372, in _jump_to
self._display_function(function)
File "F:\angr\angr-management\angrmanagement\ui\views\disassembly_view.py",
line 343, in _display_function
vr = self.workspace.instance.project.analyses.VariableRecoveryFast(the_func)
File "f:\angr\angr\angr\analyses\analysis.py", line 109, in __call__
oself.__init__(*args, **kwargs)
File
"f:\angr\angr\angr\analyses\variable_recovery\variable_recovery_fast.py", line
618, in __init__
self._analyze()
File "f:\angr\angr\angr\analyses\forward_analysis.py", line 557, in _analyze
self._analysis_core_graph()
File "f:\angr\angr\angr\analyses\forward_analysis.py", line 580, in
_analysis_core_graph
changed, output_state = self._run_on_node(n, job_state)
File
"f:\angr\angr\angr\analyses\variable_recovery\variable_recovery_fast.py", line
712, in _run_on_node
input_state = prev_state.merge(input_state, successor=node.addr)
File
"f:\angr\angr\angr\analyses\variable_recovery\variable_recovery_fast.py", line
488, in merge
merged_register_region =
self.register_region.copy().replace(replacements).merge(other.register_region,
File "f:\angr\angr\angr\keyed_region.py", line 159, in copy
kr._object_mapping = self._object_mapping.copy()
File "D:\My Program Files\Python37\lib\weakref.py", line 174, in copy
for key, wr in self.data.items():
RuntimeError: dictionary changed size during iteration
--
I went ahead and read the related methods in Lib\weakref.py, and it seems to me
that the WeakValueDictionary.copy() method is missing the protection of an
_IterationGuard: It is iterating through self.data.items(), which, might have
entries removed because of GC during the iteration.
It seems that this crash can be fixed by wrapping the iteration with `with
_IterationGuard(self):`. It worked for me in my tests.
If my above analysis is correct, the following methods all require protection
of _IterationGuard (which are currently missing):
- WeakValueDictionary.copy()
- WeakValueDictionary.__deepcopy__()
- WeakKeyDictionary.copy()
- WeakKeyDictionary.__deepcopy__()
Please let me know if this is a legitimate issue, in which case I will be happy
to provide a patch. Thanks.
--
components: Library (Lib)
messages: 332734
nosy: Fish Wang
priority: normal
severity: normal
status: open
title: "RuntimeError: Dictionary changed size during iteration" when copying a
WeakValueDictionary
type: crash
versions: Python 3.7
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<https://bugs.python.org/issue35615>
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