"should have" been added here when they were added to lists).

when that test is doomed to deadlock.

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.

visit_finalizer_reachable since it's the same as visit_reachable.
Rename visit_reachable to visit_move.  Objects can now have the GC type
flag set, reachable by tp_traverse and not be in a GC linked list.  This
should make the collector more robust and easier to use by extension
module writers.  Add memory management functions for container objects
(new, del, resize).

the setup script is running from inside Vim.

the old flag to still compile.  Remove the PyType_BASICSIZE and
PyType_SET_BASICSIZE macros.  Add PyObject_GC_New, PyObject_GC_NewVar,
PyObject_GC_Resize, PyObject_GC_Del, PyObject_GC_Track,
PyObject_GC_UnTrack.  Part of SF patch #421893.

the old flag to still compile.

try/except or try/finally.

Previous versions had only track SETUP_LOOP blocks and ignored the
exception part.  This meant that it allowed continue inside a
try/except but generated buggy code.  Now it does the right thing.

Add CONTINUE_LOOP to the list of unconditional transfers

pyport.h:  typedef a new Py_intptr_t type.
    DELICATE ASSUMPTION:  That HAVE_UINTPTR_T implies intptr_t is
    available as well as uintptr_t.  If that turns out not to be
    true, things must get uglier (C99 wants both, so I think it's
    an assumption we're *likely* to get away with).
thread_nt.h, PyThread_start_new_thread:  MS _beginthread is documented
    as returning unsigned long; no idea why uintptr_t was being used.
Others:  Always use Py_[u]intptr_t, never [u]intptr_t directly.

starts a new line.

Also fix undetected typo in visitDict() -- uncovered by recent change
to add lineno attrs to atoms.

XXX The code is still widely inaccurate, but most (all?) of the time
it's an overestimate.

in which case it will hang because the import lock is already held
by the main thread.

As the doc string for _lookupName() explains:

    This routine uses a list instead of a dictionary, because a
    dictionary can't store two different keys if the keys have the
    same value but different types, e.g. 2 and 2L.  The compiler
    must treat these two separately, so it does an explicit type
    comparison before comparing the values.