Issue #16602: When a weakref's target was part of a long deallocation chain, the...

Thanks to Eugene Toder for diagnosing and reporting the issue.

diff --cc Lib/test/test_weakref.py
Simple merge

diff --cc Misc/NEWS
index 7dab2cd03a3d514c76435aa84a97c9cbb3decdab,b26d20b54dd58f514306e16a6b52071c52e78e28..cc4f9929ed7b7e245cd10b7ac7d7a02ffdbca7f7
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -10,19 -12,15 +10,23 @@@ What's New in Python 3.4.0 Alpha 1
  Core and Builtins
  -----------------
  
 -- Issue #16416: On Mac OS X, operating system data are now always
 -  encoded/decoded to/from UTF-8/surrogateescape, instead of the locale encoding
 -  (which may be ASCII if no locale environment variable is set), to avoid
 -  inconsistencies with os.fsencode() and os.fsdecode() functions which are
 -  already using UTF-8/surrogateescape.
+ - Issue #16602: When a weakref's target was part of a long deallocation
+   chain, the object could remain reachable through its weakref even though
+   its refcount had dropped to zero.
+ 
 +- Issue #16495: Remove extraneous NULL encoding check from bytes_decode().
 +
 +- Issue #16619: Create NameConstant AST class to represent None, True, and False
 +  literals. As a result, these constants are never loaded at runtime from
 +  builtins.
 +
 +- Issue #16455: On FreeBSD and Solaris, if the locale is C, the
 +  ASCII/surrogateescape codec is now used, instead of the locale encoding, to
 +  decode the command line arguments. This change fixes inconsistencies with
 +  os.fsencode() and os.fsdecode() because these operating systems announces an
 +  ASCII locale encoding, whereas the ISO-8859-1 encoding is used in practice.
 +
 +- Issue #16562: Optimize dict equality testing.  Patch by Serhiy Storchaka.
  
  - Issue #16588: Silence unused-but-set warnings in Python/thread_pthread