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__dict__ slot for string subtypes.

subtype_dealloc(): properly use _PyObject_GetDictPtr() to get the
(potentially negative) dict offset.  Don't copy things into local
variables that are used only once.

type_new(): properly calculate a negative dict offset when tp_itemsize
is nonzero.  The __dict__ attribute, if present, is now a calculated
attribute rather than a structure member.

If tp_itemsize of the basetype is nonzero, only allow empty __slots__
(declaring that no __dict__ should be added), and don't add a weakref
offset.

In particular, the second argument can now be a subclass of the first
as well (normally it must be an instance though).

Dunno why I didn't catch this before.

directly.

don't use getattr, but only look in the dict of the type and base types.
This prevents picking up all sorts of weird stuff, including things defined
by the metaclass when the object is a class (type).

For this purpose, a helper function lookup_method() was added.  One or two
other places also use this.

into a hardcoded char* buffer.

Closes patch #454743.

super(type) -> unbound super object
super(type, obj) -> bound super object; requires isinstance(obj, type)

Typical use to call a cooperative superclass method:

class C(B):
    def meth(self, arg):
        super(C, self).meth(arg);

Thomas Hellor on python-dev).

slot_tp_descr_set(): if value is NULL, call __del__ instead of
__set__.

level to 2.2a2+

interpretation of negative indices, since neither the sq_*item slots
nor the slot_ wrappers do this.  (Slices are a different story, there
the size wrapping is done too early.)

Classes that don't use __slots__ have a __weakref__ member added in
the same way as __dict__ is added (i.e. only if the base didn't
already have one).  Classes using __slots__ can enable weak
referenceability by adding '__weakref__' to the __slots__ list.

Renamed the __weaklistoffset__ class member to __weakrefoffset__ --
it's not always a list, it seems.  (Is tp_weaklistoffset a historical
misnomer, or do I misunderstand this?)

the class dict).  Anything but a nonnegative int in either place is
*ignored* (before, a non-Boolean was an error).  The default is still
static -- in a comparative test, Jeremy's Tools/compiler package ran
twice as slow (compiling itself) using dynamic as the default.  (The
static version, which requires a few tweaks to avoid modifying class
variables, runs at about the same speed as the classic version.)

slot_tp_descr_get(): this also needed fallback behavior.

slot_tp_getattro(): remove a debug fprintf() call.

the metatype passed in as an argument.  This prevents infinite
recursion when a metatype written in Python calls type.__new__() as a
"super" call.

Also tweaked some comments.

type_repr() for when to show or not to show it).

- type_module(), type_name(): if tp_name contains one or more period,
  the part before the last period is __module__, the part after that
  is __name__.  Otherwise, for non-heap types, __module__ is
  "__builtin__".  For heap types, __module__ is looked up in
  tp_defined.

- type_new(): heap types have their __module__ set from
  globals().__name__; a pre-existing __module__ in their dict is not
  overridden.  This is not inherited.

- type_repr(): if __module__ exists and is not "__builtin__", it is
  included in the string representation (just as it already is for
  classes).  For example <type '__main__.C'>.

- descrobject.c:descr_check(): only believe None means the same as
  NULL if the type given is None's type.

- typeobject.c:wrap_descr_get(): don't "conventiently" default an
  absent type to the type of the object argument.  Let the called
  function figure it out.

  operators for which a default implementation exist now work, both in
  dynamic classes and in static classes, overridden or not.  This
  affects __repr__, __str__, __hash__, __contains__, __nonzero__,
  __cmp__, and the rich comparisons (__lt__ etc.).  For dynamic
  classes, this meant copying a lot of code from classobject!  (XXX
  There are still some holes, because the comparison code in object.c
  uses PyInstance_Check(), meaning new-style classes don't get the
  same dispensation.  This needs more thinking.)

- Add object.__hash__, object.__repr__, object.__str__.  The __str__
  dispatcher now calls the __repr__ dispatcher, as it should.

- For static classes, the tp_compare, tp_richcompare and tp_hash slots
  are now inherited together, or not at all.  (XXX I fear there are
  still some situations where you can inherit __hash__ when you
  shouldn't, but mostly it's OK now, and I think there's no way we can
  get that 100% right.)

be inherited in inherit_special(), otherwise dynamic types don't
inherit these.

Also added some XXX comments about open ends.

XXX There are still some loose ends: repr(), str(), hash() and
comparisons don't inherit a default implementation from object.  This
must be resolved similarly to the way it's resolved for classic
instances.

XXX This is not sufficient: if a dynamic class has no __repr__ method
(for instance), but later one is added, that doesn't add a tp_repr
slot, so repr() doesn't call the __repr__ method.  To make this work,
I'll have to add default implementations of several slots to 'object'.

XXX Also, dynamic types currently only inherit slots from their
dominant base.

  problem).  inherit_slots() is split in two parts: inherit_special()
  which inherits the flags and a few very special members from the
  dominant base; inherit_slots() which inherits only regular slots,
  and is now called for each base in the MRO in turn.  These are now
  both void functions since they don't have error returns.

- Added object.__setitem__() back -- for the same reason as
  object.__new__(): a subclass of object should be able to call
  object.__new__().

- add_wrappers() was moved around to be closer to where it is used (it
  was defined together with add_methods() etc., but has nothing to do
  with these).

it possible to detect recursive calls early (as opposed to when the
stack overflows :-).

inherited unless *both*: (a) the base type is 'object', and (b) the
subtype is not a "heap" type.

bit.  For one, this class:

    class C(object):
        def __new__(myclass, ...): ...

would have no way to call the __new__ method of its base class, and
the workaround (to create an intermediate base class whose __new__ you
can call) is ugly.

So, I've come up with a better solution that restores object.__new__,
but still solves the original problem, which is that built-in and
extension types shouldn't inherit object.__new__.  The solution is
simple: only "heap types" inherit tp_new.  Simpler, less code,
perfect!

division.  The basic binary operators now all correctly call the
__rxxx__ variant when they should.

In type_new(), I now make the new type a new-style number unless it
inherits from an old-style number that has numeric methods.

By way of cosmetics, I've changed the signatures of the SLOT<i> macros
to take actual function names and operator names as strings, rather
than rely on C preprocessor symbol manipulations.  This makes the
calls slightly more verbose, but greatly helps simple searches through
the file: you can now find out where "__radd__" is used or where the
function slot_nb_power() is defined and where it is used.

Removed extraneous semicolons that caused a gazzilion "empty declaration" warnings in the MetroWerks compiler.

- Add an explicit call to PyType_Ready(&PyList_Type) to pythonrun.c
  (just for the heck of it, really -- we should either explicitly
  ready all types, or none).

- Add comment blocks explaining add_operators() and override_slots().
  (This file could use some more explaining, but this is all I had
  breath for today. :)

- Renamed the argument 'base' of add_wrappers() to 'wraps' because
  it's not a base class (which is what the 'base' identifier is used
  for elsewhere).

Small nits:

- Fix add_tp_new_wrapper() to avoid overwriting an existing __new__
  descriptor in tp_defined.

- In add_operators(), check the return value of add_tp_new_wrapper().

Functional change:

- Remove the tp_new functionality from PyBaseObject_Type; this means
  you can no longer instantiate the 'object' type.  It's only useful
  as a base class.

- To make up for the above loss, add tp_new to dynamic types.  This
  has to be done in a hackish way (after override_slots() has been
  called, with an explicit call to add_tp_new_wrapper() at the very
  end) because otherwise I ran into recursive calls of slot_tp_new().
  Sigh.

problem brought up in SF bug #444229.

case of objects with equal types which support tp_compare. Give
type objects a tp_compare function.
Also add c<0 tests before a few PyErr_Occurred tests.

This should match the situation in the 1.6b1 tree.