In the TRACE_REFS version of the code, call _Py_NewReference() instead
of INCREF to bump the refcount from zero to one.

When exiting the function, don't DECREF the object back to zero
refcount, as that will reinvoke the object's deallocation function.
XXX Why did this ever work?

    No need to generate code that is not needed!

fixed ZClass-related type-checking breakage introduced in reformatting in rev 1.45. I guess there are no unit tests for ZClasses?

I think it's safe to run this code without extra checking.

constructor, since it is ignored and there is no current plan to
support two caches with almost-but-not-quite-the-same arguments.

This change has effects in many files.  The Connection and DB don't
pass this argument and don't bother setting it explicitly when it is
reset via DB APIs like setCacheDeactivateAfter().  XXX These APIs
remain, since existing code may depend on them, but they have no
effect.

New policy in cPersistence.c: A Persistent object can't have its
_p_jar set or deleted once it is in a cache.  Persistent already
implemented this policy for _p_oid; it seems safer to do the same for
the jar.

Add ringlen() method to cache objects (implemented as cc_ringlen).
This returns the length of the doubly linked list of non-ghost
objects.  Same as len(cache.lru_items()), but more efficient.  Only
used for testing at the moment.

In ring_corrupt(), don't raise a new exception if one has already been
set.  The old behavior masked useful information about the original
error / traceback.

Implement behavior for minimize() and full_sweep() as discussed on
zodb-dev.  minimize() ghostifies all unmodified objects.  full_sweep()
with age==0 is the same as minimize(), otherwise it's the same as
incrgc().

Reformat and/or reindent lots of code.

Use PyObject_Compare() instead of PyObject_Cmp() because it has a
simpler return value.

Fix a few more PyDict_SetItem() and PyDict_DelItem() calls to make
correct check for error return.

    The rationale is that this is an internal detail of the cache
    implementation called by Per_dealloc().  It's nice to make it
    fast, and it's good to prevent it from being called with anything
    other than an about-to-be-freed object.

    As a result of it being in the C API, omit tests of refcounts.  We
    would have been in Per_dealloc() otherwise.

    Initialize the percachdel slot of cPersistenceAPIstruct to NULL in
    cPersistence.  In cPickleCache, import the CObject and fill in the
    struct.

Also, reformat many of the comments so that all the text starts to the
right of the /*.

Fiddle the text of the placeholder comment.  I think I understand it
now :-).

Add an XXX comment about the "old" cache API e.g. fullsweep and
reallyfullsweep.

Fix cc_get().  object_from_oid() doesn't ever set an exception.

Remove a Py_FatalError() check from the end of a module init
function.  We don't do that anymore.

takes an exception object as its first argument, and the return value
should be a -1 instead of NULL (this function's signature has an int
return).

I'm surprised no one else's build caught this compiler warning.

(Thanks for the comments, Toby!)

Add check that argument to cc_ass_sub() is a string.  The cache maps
oids to objects, and oids must be strings for now.

Re-indent a bunch of code.

Replace an XXX comment about v->oid with a comment explaining why
getattr is necessary.

check_ring() rename to ring_corrupt() since that matches the return
semantics a bit better.

scan_gc_items(): Get rid of the placeholder, which just seemed like a
confusing way to stash here->next until after the PyObject_SetAttr()
call.

did you use?

A few substantive changes:

Split internals of cc_ass_sub() into two smaller function
cc_add_item() and cc_del_item(), removing several levels of
indentation in the process.

Fix incorrect check for return value from PyDict_SetItem().

Remove use of staticforward.

Avoid forward reference to Cctype by defining newccobject after type
struct.

Define the contents of ccobject_head_struct via CACHE_HEAD macro.
Don't rely on two different files to define a struct with the same
layout by convention.

Remove many levels of parentheses from the HOME and NON_GHOST_COUNT
macros.

Replace KEEP_THIS_ONE_AROUND_FOR_A_WHILE() macro with a call to the
accessed() function.  (Who comes up with these names :-).

Remove include of string.h in cPersistence.c.

Expand cPersistent_HEAD macro so that it has one line for each
attribute!

Use typedef to define PerCache as "struct ccobject_head_struct" and
use this for the entry cache slot in cPersistent_HEAD instead of
PyObject *.

In cPickleCache.c, reflow a bunch of long lines, add some whitespace,
and an XXX comment explaining that I don't understand a different
comment.

Fix SF bug #516768 reported by Dave Wallace.

Replace use of PyMem_DEL() with PyObject_Del() on object dealloc
functions.  The use of PyMem_DEL() is incorrect for object
deallocation, because it only ever calls the low-level free().  If a
custom allocator like pymalloc is used, it needs to be called to free
the memory.

Summary of changes:

- Add function gc_all_items() to call gc_item() on everything in
  dict.  This factors out common code in all the gc methods.

- Add check_size() function that factors out code to check cache size
  before starting a gc.

- Simplify argument processing in cc_invalidate(), avoiding a second
  call to PyArg_ParseTuple() when argument is a sequence instead of a
  dictionary.

- Chance code to reflect belief that NULL return from PyDict_GetItem()
  does not set exception, except in cases that don't apply for the
  pickle cache like comparing a string with high-order bit set to a
  Unicode object.

- Use if (!expr) instead of UNLESS().

- Remove all statements from conditionals.

- Reformat to 4 spaces and Python-style brace placement.

- Put whitespace around operators and after commas.

decref the revision string, added to the module dict with the keys
"__version__".  This fixes a small leaks detected by Insure.

Also, at the end of the function, we do a PyErr_Occurred() check and
throw a fatal error if true.  This makes this module's init function
more in line with other init functions in this package.

DB.py: typo in comment
cPickleCache.c: fix cache sweep logic
cPersistence.c: small performance changes

cPersistence.c to avoid compiler warnings in cPickleCache and
coptimizations.

add parens and module doc string

ignored and an indeterminate value used instead.

a transaction could, in rare cases cause inconsistent computations.

Also added argument to incrgc to allow more aggressive GC.

moving parts.

The minimize machinery didn;t use the correct time units.

The incremental GC had some bugs that made it too conservative.

used an incorrect variable name.