Issue #20317: Don't create a reference loop in ExitStack
diff --git a/Lib/contextlib.py b/Lib/contextlib.py
index f8e026b..f878285 100644
--- a/Lib/contextlib.py
+++ b/Lib/contextlib.py
@@ -231,11 +231,19 @@
# 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