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

Closes bug #1377858.  Already backported.

with PyObject_CallFunctionObjArgs, which is 30% faster.

using a custom, nearly-identical macro. This probably changes how some of
these functions are compiled, which may result in fractionally slower (or
faster) execution. Considering the nature of traversal, visiting much of the
address space in unpredictable patterns, I'd argue the code readability and
maintainability is well worth it ;P

(reviewed by Neal Norwitz)

In C++, it's an error to pass a string literal to a char* function
without a const_cast().  Rather than require every C++ extension
module to put a cast around string literals, fix the API to state the
const-ness.

I focused on parts of the API where people usually pass literals:
PyArg_ParseTuple() and friends, Py_BuildValue(), PyMethodDef, the type
slots, etc.  Predictably, there were a large set of functions that
needed to be fixed as a result of these changes.  The most pervasive
change was to make the keyword args list passed to
PyArg_ParseTupleAndKewords() to be a const char *kwlist[].

One cast was required as a result of the changes:  A type object
mallocs the memory for its tp_doc slot and later frees it.
PyTypeObject says that tp_doc is const char *; but if the type was
created by type_new(), we know it is safe to cast to char *.

In cyclic gc, clear weakrefs to unreachable objects before allowing any
Python code (weakref callbacks or __del__ methods) to run.

This is a critical bugfix, affecting all versions of Python since weakrefs
were introduced.  I'll backport to 2.3.

possible that the callback-less flavors of the ref or proxy could have
been added during GC, so we don't want to replace them.

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.

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.

weakref ref and proxy objects; None was not being treated as identical to
NULL, though it was documented as equivalent.

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.

"print repr(proxy(a))" and "proxy(a)" at an interactive prompt.
Closes SF bug #722763.

  the referenced object, if it has one.

Also use %p to format pointers consistently, and use <weakproxy ...>
in proxy_repr(), to match the type name.

Part of fixing SF bug #591704.

management bug.  Also, move some duplicated code into the new_weakref
fucntion.

both are proxy objects.

references, we do not allow any outstanding exceptions "leak" into the
callback's execution state.
This closes SF bug #478534.

PyOS_snprintf() for buffer overrun avoidance.

the left-hand operand may not be the proxy in all cases.  If it isn't,
we end up doing two things: a) unwrapping something that isn't a
PyWeakReference (later resulting in a core dump) and b) passing a
proxy as the right-hand operand anyway, even though that can't be
handled by the actual handler (maybe eventually causing a core dump).

This is fixed by always unwrapping all the proxies involved before
passing anything to the actual handler.

performance changes since the affected functions are not expected to be
used frequently, but reduces the volume of code.

void function.

                   before calling any callbacks.  This is important
                   since the callback objects only look at themselves
                   to determine that they are invalide.  This change
                   avoids a segfault when callbacks use a different
                   reference to an object in the process of being
                   deallocated.

This fixes SF bug #415660.

tracked as soon as it is clear; this can decrease the number of roots for
the cycle detector sooner rather than later in applications which hold on
to weak references beyond the time of the invalidation.

        comments to reflect reality.

so make it void.