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Issue #20317: Don't create a reference loop in ExitStack

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Nick Coghlan 2014-01-22 22:24:46 +10:00
parent 0e3b0e397e
commit 09761e7c9c
3 changed files with 38 additions and 1 deletions
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10
Lib/contextlib.py
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@ -231,11 +231,19 @@ class ExitStack(object):
# we were actually nesting multiple with statements
frame_exc = sys.exc_info()[1]
def _fix_exception_context(new_exc, old_exc):
# Context isn't what we want, so find the end of the chain
while 1:
exc_context = new_exc.__context__
if exc_context in (None, frame_exc):
if exc_context is old_exc:
# Context is already set correctly (see issue 20317)
return
if exc_context is None or exc_context is frame_exc:
break
details = id(new_exc), id(old_exc), id(exc_context)
raise Exception(str(details))
new_exc = exc_context
# Change the end of the chain to point to the exception
# we expect it to reference
new_exc.__context__ = old_exc
# Callbacks are invoked in LIFO order to match the behaviour of