Reviewers: Amaury, Antoine, Benjamin

seen after a "import multiprocessing.reduction"

An instance of a weakref subclass can have attributes.
If such a weakref holds the only strong reference to the object,
deleting the weakref will delete the object. In this case,
the callback must not be called, because the ref object is being deleted!

Patch only fixes new-style classes; classic classes still buggy.

Closes bug #1377858.  Already backported.

Remove various dependencies on dictionary order in the standard library
tests, and one (clearly an oversight, potentially critical) in the
standard library itself - base64.py.

Remaining open issues:
 * test_extcall is an output test, messy to make robust
 * tarfile.py has a potential bug here, but I'm not familiar
   enough with this code.  Filed in as SF bug #1496501.
 * urllib2.HTTPPasswordMgr() returns a random result if there is more
   than one matching root path.  I'm asking python-dev for
   clarification...

weakref.WeakKeyDictionary and weakref.WeakValueDictionary

Need to return -1 on error.

Needs backport.

- weakref.ref and weakref.ReferenceType will become aliases for each
  other

- weakref.ref will be a modern, new-style class with proper __new__
  and __init__ methods

- weakref.WeakValueDictionary will have a lighter memory footprint,
  using a new weakref.ref subclass to associate the key with the
  value, allowing us to have only a single object of overhead for each
  dictionary entry (currently, there are 3 objects of overhead per
  entry: a weakref to the value, a weakref to the dictionary, and a
  function object used as a weakref callback; the weakref to the
  dictionary could be avoided without this change)

- a new macro, PyWeakref_CheckRefExact(), will be added

- PyWeakref_CheckRef() will check for subclasses of weakref.ref

This closes SF patch #983019.

same as for the string and sequence tests.

mapping tests as possible in mapping_test.py and reuse the tests in
test_dict.py, test_userdict.py, test_weakref.py, test_os.py and test_shelve.py.
From SF patch #736962.

(re-using an existing test object class) no longer triggered the
original segfault when the fix was backed out; restoring the local
test object class to make the test effective

the assignment of the ref created at the end does not affect the test,
since the segfault happended before weakref.ref() returned; removing
the assignment

From SF patch #852334.

the same object to be collected by the cyclic GC support if they are
only referenced by a cycle.  If the weakref being collected was one of
the weakrefs without callbacks, some local variables for the
constructor became invalid and have to be re-computed.

The test caused a segfault under a debug build without the fix applied.

  PyWeakref_NewProxy() constructors from the C API
- elaborate the getweakrefcount() and getweakrefs() tests slightly

Port test_md5.py to PyUnit.

(Written by Neal Norwitz; from SF patch 736962)

(Backport candidate)

Also SF patch 843455.

This is a critical bugfix.
I'll backport to 2.3 maint, but not beyond that.  The bugs this fixes
have been there since weakrefs were introduced.

* Install the unittests, docs, newsitem, include file, and makefile update.
* Exercise the new functions whereever sets.py was being used.

Includes the docs for libfuncs.tex.  Separate docs for the types are
forthcoming.

expanded the test case with a piece that needs the more-complete fix.

I'll backport this to 2.3 maint.

subtype_dealloc():  This left the dying object exposed to gc, so that
if cyclic gc triggered during the weakref callback, gc tried to delete
the dying object a second time.  That's a disaster.  subtype_dealloc()
had a (I hope!) unique problem here, as every normal dealloc routine
untracks the object (from gc) before fiddling with weakrefs etc.  But
subtype_dealloc has obscure technical reasons for re-registering the
dying object with gc (already explained in a large comment block at
the bottom of the function).

The fix amounts to simply refraining from reregistering the dying object
with gc until after the weakref callback (if any) has been called.

This is a critical bug (hard to predict, and causes seemingly random
memory corruption when it occurs).  I'll backport it to 2.3 later.

- wrap some long lines
- shorten others
- fix indentation

Python-Dev.  Fixed typos in test comments.  Added some trivial new test
guts to show the parallelism (now) among __delitem__, __setitem__ and
__getitem__ wrt error conditions.

Still a bugfix candidate for 2.2.3 final, but waiting for Fred to get a
chance to chime in.

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.

Improves clarity and brevity.

and test_support.run_classtests() into run_unittest()
and use it wherever possible.

Also don't use "from test.test_support import ...", but
"from test import test_support" in a few spots.

From SF patch #662807.

* Adds missing pop() methods to weakref.py
* Expands test suite to broaden coverage of objects with
  a mapping interface.

Contributed by Sebastien Keim.

unittest.makeSuite() rather than loader.loadTestsFromTestCase().

imports e.g. test_support must do so using an absolute package name
such as "import test.test_support" or "from test import test_support".

This also updates the README in Lib/test, and gets rid of the
duplicate data dirctory in Lib/test/data (replaced by
Lib/email/test/data).

Now Tim and Jack can have at it. :)

The WeakKeyDictionary constructor didn't work when a dict arg was
given.  Fixed by moving a line.  Also adding a unit test.

Bugfix candidate.

callback.

referenced, WeakKeyDictionary.has_key() should return 0 instead of raising
TypeError.

handlers.  This was fixed in Objects/weakrefobject.c 1.2.

allows using the tests with unittest.py as a script.  The tests will
still run when run as a script themselves.