METH_NOARGS functions need only a single argument but they are cast
into a PyCFunction, which takes two arguments.  This triggers an
invalid function cast warning in gcc8 due to the argument mismatch.
Fix this by adding a dummy unused argument.

Add two new private APIs: _PyObject_LookupAttr() and _PyObject_LookupAttrId()

now becames exhausted after advancing the groupby iterator.

Affected classes are bytearray, array, deque, defaultdict, count and repeat.

This function returns the last component of tp_name after a dot.
Returns tp_name itself if it doesn't contain a dot.

Error messages when pass keyword arguments to some builtins that
don't support keyword arguments contained double parenthesis: "()()".
The regression was introduced by bpo-30534.

* bpo-30537: use PyNumber in itertools instead of PyLong

* bpo-30537: revert changes except to islice_new

* bpo-30537: test itertools.islice and add entry to Misc/NEWS

raised an error.

Replace them with using concrete types API that never fails if appropriate.

Fix the use of recursion in itertools.chain.from_iterable. Using recursion
is unnecessary, and can easily cause stack overflows, especially when
building in low optimization modes or with Py_DEBUG enabled.

Issue #28858: The change b9c9691c72c5 introduced a regression. It seems like
_PyObject_CallArg1() uses more stack memory than
PyObject_CallFunctionObjArgs().

* PyObject_CallFunctionObjArgs(func, NULL) => _PyObject_CallNoArg(func)
* PyObject_CallFunctionObjArgs(func, arg, NULL) => _PyObject_CallArg1(func, arg)

PyObject_CallFunctionObjArgs() allocates 40 bytes on the C stack and requires
extra work to "parse" C arguments to build a C array of PyObject*.

_PyObject_CallNoArg() and _PyObject_CallArg1() are simpler and don't allocate
memory on the C stack.

This change is part of the fastcall project. The change on listsort() is
related to the issue #23507.

incorrect pickle data.  Based on patch by John Leitch.

between 1.0 and 2.0 to 1.

Based on patch by Ville Skyttä.

in places where Py_DECREF was used.

Old code is correct, but with Py_SETREF and Py_CLEAR it can be cleaner.
This patch doesn't fix bugs and hence there is no need to backport it.

The patch is automatically generated, it replaces the code that uses Py_CLEAR.

macro Py_SETREF.

This allows sys.getsize() to work correctly with their subclasses with
__slots__ defined.

invalid memory.

Will backport after the 3.6 release is done.