SF 742860: WeakKeyDictionary __delitem__ uses iterkeys
Someone review this, please! Final releases are getting close, Fred
(the weakref guy) won't be around until Tuesday, and the pre-patch
code can indeed raise spurious RuntimeErrors in the presence of
threads or mutating comparison functions.
See the bug report for my confusions: I can't see any reason for why
__delitem__ iterated over the keys. The new one-liner implementation
is much faster, can't raise RuntimeError, and should be better-behaved
in all respects wrt threads.
New tests test_weak_keyed_bad_delitem and
test_weak_keyed_cascading_deletes fail before this patch.
Bugfix candidate for 2.2.3 too, if someone else agrees with this patch.
diff --git a/Misc/NEWS b/Misc/NEWS
index a63f022..bc15f42 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,12 @@
Core and builtins
-----------------
+- SF bug 742860: WeakKeyDictionary __delitem__ uses iterkeys. This
+ wasn't as threadsafe as it should be, was very inefficient, and could
+ raise RuntimeError if another thread mutated the dict during
+ __delitem__, or if a comparison function mutated it. A new
+ implementation of WeakKeyDictionary.__delitem__ repairs all that.
+
- SF bug 705231: builtin pow() no longer lets the platform C pow()
raise -1.0 to integer powers, because (at least) glibc gets it wrong
in some cases. The result should be -1.0 if the power is odd and 1.0