Move cc_oid_unreferenced() into the C API and out of Python.

    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.

src/Persistence/cPersistence.c

@@ -14,11 +14,10 @@
 static char cPersistence_doc_string[] = 
 "Defines Persistent mixin class for persistent objects.\n"
 "\n"
-"$Id: cPersistence.c,v 1.57 2002/04/02 22:46:48 jeremy Exp $\n";
+"$Id: cPersistence.c,v 1.58 2002/04/05 01:12:48 jeremy Exp $\n";
 
 #include "cPersistence.h"
 
-/* XXX What is this structure used for? */
 struct ccobject_head_struct {
     CACHE_HEAD
 };
@@ -202,15 +201,11 @@ deallocated(cPersistentObject *self)
     if (self->state >= 0) 
 	ghostify(self);
     if (self->cache) {
-        PyObject *v;
-
-	/* XXX should just add this to the C API struct */
-	v = PyObject_CallMethod((PyObject *)self->cache, 
-				"_oid_unreferenced", "O", self->oid);
-        if (v == NULL)
-	    PyErr_Clear(); /* I dont think this should ever happen */
-	else
-	    Py_DECREF(v);
+	/* XXX This function shouldn't be able to fail? If not, maybe
+	   it shouldn't set an exception either.
+	*/
+	if (cPersistenceCAPI->percachedel(self->cache, self->oid) < 0)
+	    PyErr_Clear(); /* I don't think this should ever happen */
     }
     Py_XDECREF(self->jar);
     Py_XDECREF(self->oid);
@@ -256,19 +251,22 @@ changed(cPersistentObject *self)
 static PyObject *
 Per___changed__(cPersistentObject *self, PyObject *args)
 {
-  PyObject *v=0;
+    PyObject *v = NULL;
 
-  if (args && ! PyArg_ParseTuple(args, "|O",&v)) return NULL;
-  if (! v) return PyObject_GetAttr(OBJECT(self), py__p_changed);
+    if (args && !PyArg_ParseTuple(args, "|O:__changed__", &v)) 
+	return NULL;
+    if (!v) 
+	return PyObject_GetAttr(OBJECT(self), py__p_changed);
 
-  if (PyObject_IsTrue(v)) 
-    {
-      if (changed(self) < 0) return NULL;
+    if (PyObject_IsTrue(v)) {
+	if (changed(self) < 0) 
+	    return NULL;
     }
-  else if (self->state >= 0) self->state=cPersistent_UPTODATE_STATE;
+    else if (self->state >= 0) 
+	self->state = cPersistent_UPTODATE_STATE;
 
-  Py_INCREF(Py_None);
-  return Py_None;
+    Py_INCREF(Py_None);
+    return Py_None;
 }
 
 static PyObject *
@@ -295,7 +293,7 @@ Per__p_deactivate(cPersistentObject *self, PyObject *args)
     }
 
   /* need to delay releasing the last reference on instance attributes
-  until after we have finished accounting for losing our state */
+     until after we have finished accounting for losing our state */
   if (dict2)
   {
       PyDict_Clear(dict2);
@@ -807,6 +805,7 @@ truecPersistenceCAPI = {
   deallocated,
   (intfunctionwithpythonarg)Per_setstate,
   (pergetattr)Per_getattr,
+  NULL
 };
 
 void
@@ -826,7 +825,8 @@ initcPersistence(void)
   Py_DECREF(m);
   Py_DECREF(s);
 
-  if (init_strings() < 0) return;
+  if (init_strings() < 0) 
+      return;
 
   m = Py_InitModule4("cPersistence", cP_methods, cPersistence_doc_string,
 		     (PyObject*)NULL, PYTHON_API_VERSION);
@@ -837,12 +837,8 @@ initcPersistence(void)
   PyExtensionClass_Export(d, "Persistent",  Pertype);
   PyExtensionClass_Export(d, "Overridable", Overridable);
 
-  cPersistenceCAPI=&truecPersistenceCAPI;
-  s = PyCObject_FromVoidPtr(cPersistenceCAPI,NULL);
+  cPersistenceCAPI = &truecPersistenceCAPI;
+  s = PyCObject_FromVoidPtr(cPersistenceCAPI, NULL);
   PyDict_SetItemString(d, "CAPI", s);
   Py_XDECREF(s);
-
-  /* Check for errors */
-  if (PyErr_Occurred())
-    Py_FatalError("can't initialize module cPersistence");
 }

src/Persistence/cPersistence.h

@@ -18,6 +18,12 @@
 #include "ExtensionClass.h"
 #include <time.h>
 
+typedef struct CPersistentRing_struct
+{
+    struct CPersistentRing_struct *prev;
+    struct CPersistentRing_struct *next;
+} CPersistentRing;
+
 #define CACHE_HEAD \
     PyObject_HEAD \
     CPersistentRing ring_home; \
@@ -42,30 +48,26 @@ typedef struct ccobject_head_struct PerCache;
 #define cPersistent_CHANGED_STATE 1
 #define cPersistent_STICKY_STATE 2
 
-typedef struct CPersistentRing_struct
-{
-    struct CPersistentRing_struct *prev;
-    struct CPersistentRing_struct *next;
-} CPersistentRing;
-
 typedef struct {
     cPersistent_HEAD
 } cPersistentObject;
 
 typedef int (*persetattr)(PyObject *, PyObject*, PyObject *, setattrofunc);
 typedef PyObject *(*pergetattr)(PyObject *, PyObject*, char *, getattrofunc);
+typedef int (*percachedelfunc)(PerCache *, PyObject *);
 
 typedef struct {
-  PyMethodChain *methods;
-  getattrofunc getattro;
-  setattrofunc setattro;
-  int (*changed)(cPersistentObject*);
-  void (*accessed)(cPersistentObject*);
-  void (*ghostify)(cPersistentObject*);
-  void (*deallocated)(cPersistentObject*);
-  int (*setstate)(PyObject*);
-  pergetattr pergetattro;
-  persetattr persetattro;
+    PyMethodChain *methods;
+    getattrofunc getattro;
+    setattrofunc setattro;
+    int (*changed)(cPersistentObject*);
+    void (*accessed)(cPersistentObject*);
+    void (*ghostify)(cPersistentObject*);
+    void (*deallocated)(cPersistentObject*);
+    int (*setstate)(PyObject*);
+    pergetattr pergetattro;
+    persetattr persetattro;
+    percachedelfunc percachedel;
 } cPersistenceCAPIstruct;
 
 #ifndef DONT_USE_CPERSISTENCECAPI

src/Persistence/cPickleCache.c

@@ -88,7 +88,7 @@ process must skip such objects, rather than deactivating them.
 static char cPickleCache_doc_string[] =
 "Defines the PickleCache used by ZODB Connection objects.\n"
 "\n"
-"$Id: cPickleCache.c,v 1.54 2002/04/04 22:02:32 bwarsaw Exp $\n";
+"$Id: cPickleCache.c,v 1.55 2002/04/05 01:12:48 jeremy Exp $\n";
 
 #define ASSIGN(V,E) {PyObject *__e; __e=(E); Py_XDECREF(V); (V)=__e;}
 #define UNLESS(E) if(!(E))
@@ -118,9 +118,9 @@ static PyObject *py__p_oid, *py_reload, *py__p_jar, *py__p_changed;
 #define ENGINE_NOISE(A) ((void)A)
 #endif
 
-/* This object is the pickle cache.  The CACHE_HEAD macro guarantees that
-layout of this struct is the same as the start of ccobject_head in
-cPersistence.c */
+/* This object is the pickle cache.  The CACHE_HEAD macro guarantees
+   that layout of this struct is the same as the start of
+   ccobject_head in cPersistence.c */
 typedef struct {
     CACHE_HEAD
     int klass_count;                         /* count of persistent classes */
@@ -156,15 +156,15 @@ static int cc_ass_sub(ccobject *self, PyObject *key, PyObject *v);
 
 /* ---------------------------------------------------------------- */
 
-static PyObject *object_from_oid(ccobject *self, PyObject *key)
 /* somewhat of a replacement for PyDict_GetItem(self->data....
    however this returns a *new* reference */
+static PyObject *
+object_from_oid(ccobject *self, PyObject *key)
 {
     PyObject *v = PyDict_GetItem(self->data, key);
-    if(!v) return NULL;
-
+    if (!v) 
+	return NULL;
     Py_INCREF(v);
-
     return v;
 }
 
@@ -263,10 +263,11 @@ scan_gc_items(ccobject *self,int target)
         if (here == &self->ring_home)
             return 0;
 
-        /* At this point we know that the ring only contains nodes from
-        persistent objects, plus our own home node. We know this because
-        the ring lock is held.  We can safely assume the current ring
-        node is a persistent object now we know it is not the home */
+        /* At this point we know that the ring only contains nodes
+	   from persistent objects, plus our own home node. We know
+	   this because the ring lock is held.  We can safely assume
+	   the current ring node is a persistent object now we know it
+	   is not the home */
         object = object_from_ring(self, here, "scan_gc_items");
         if (!object) 
 	    return -1;
@@ -277,12 +278,15 @@ scan_gc_items(ccobject *self,int target)
         else if (object->state == cPersistent_UPTODATE_STATE) {
             /* deactivate it. This is the main memory saver. */
 
-            /* Add a placeholder; a dummy node in the ring. We need to
-            do this to mark our position in the ring. All the other nodes
-            come from persistent objects, and they are all liable
-            to be deallocated before "obj._p_changed = None" returns
-            to this function. This operation is only safe when the
-            ring lock is held (and it is) */
+            /* Add a placeholder; a dummy node in the ring.  We need
+	       to do this to mark our position in the ring.  It is
+	       possible that the PyObject_SetAttr() call below will
+	       invoke an __setattr__() hook in Python.  If it does,
+	       another thread might run; if that thread accesses a
+	       persistent object and moves it to the head of the ring,
+	       it might cause the gc scan to start working from the
+	       head of the list.
+	    */
 
             placeholder.next = here->next;
             placeholder.prev = here;
@@ -315,7 +319,7 @@ scan_gc_items(ccobject *self,int target)
 static PyObject *
 lockgc(ccobject *self, int target_size)
 {
-    /* We think this is thread-safe because of the GIL, and there's nothing
+    /* This is thread-safe because of the GIL, and there's nothing
      * in between checking the ring_lock and acquiring it that calls back
      * into Python.
      */
@@ -361,16 +365,23 @@ cc_incrgc(ccobject *self, PyObject *args)
     if (!PyArg_ParseTuple(args, "|i:incrgc", &n)) 
 	return NULL;
 
-    return lockgc(self,target_size);
+    return lockgc(self, target_size);
 }
 
+/* XXX Does it make sense for full_sweep() and reallyfull_sweep() to
+   empty the cache completely?  I agree that it would if dt is 0, but
+   don't think it should for other times.  Perhaps it should just call
+   incrgc() if dt > 2; the new cache may be efficient enough that
+   incrgc() would suffice.
+*/
+
 static PyObject *
 cc_full_sweep(ccobject *self, PyObject *args)
 {
     int dt = 0;
     if (!PyArg_ParseTuple(args, "|i:full_sweep", &dt)) 
 	return NULL;
-    return lockgc(self,0);
+    return lockgc(self, 0);
 }
 
 static PyObject *
@@ -379,7 +390,7 @@ cc_reallyfull_sweep(ccobject *self, PyObject *args)
   int dt = 0;
   if (!PyArg_ParseTuple(args, "|i:reallyfull_sweep", &dt)) 
       return NULL;
-  return lockgc(self,0);
+  return lockgc(self, 0);
 }
 
 static void
@@ -460,22 +471,19 @@ cc_get(ccobject *self, PyObject *args)
 {
   PyObject *r, *key, *d=0;
 
-  UNLESS (PyArg_ParseTuple(args,"O|O", &key, &d)) return NULL;
+  if (!PyArg_ParseTuple(args, "O|O:get", &key, &d)) 
+      return NULL;
 
-  UNLESS (r=(PyObject *)object_from_oid(self, key))
-    {
-      if (d) 
-	{
-	  PyErr_Clear();
-	  r=d;
+  r = (PyObject *)object_from_oid(self, key);
+  if (!r) {
+      if (d) {
+	  r = d;
           Py_INCREF(r);
-	}
-      else
-	{
+      } else {
 	  PyErr_SetObject(PyExc_KeyError, key);
 	  return NULL;
-	}
-    }
+      }
+  }
 
   return r;
 }
@@ -522,8 +530,9 @@ cc_lru_items(ccobject *self, PyObject *args)
 	return NULL;
 
     if (self->ring_lock) {
-	/* When the ring lock is held, we have no way of know which ring nodes
-	belong to persistent objects, and which a placeholders. */
+	/* When the ring lock is held, we have no way of know which
+	   ring nodes belong to persistent objects, and which a
+	   placeholders. */
         PyErr_SetString(PyExc_ValueError,
 		".lru_items() is unavailable during garbage collection");
         return NULL;
@@ -562,40 +571,25 @@ cc_lru_items(ccobject *self, PyObject *args)
     return l;
 }
 
-static PyObject *
-cc_oid_unreferenced(ccobject *self, PyObject *args)
+static int
+cc_oid_unreferenced(ccobject *self, PyObject *oid)
 {
-    /* This is called by the persistent object deallocation
-    function when the reference count on a persistent
-    object reaches zero. We need to fix up our dictionary;
-    its reference is now dangling because we stole its
-    reference count. Be careful to not release the global
-    interpreter lock until this is complete. */
-
-    PyObject *oid, *v;
-    if (!PyArg_ParseTuple(args, "O:_oid_unreferenced", &oid)) 
-	return NULL;
+    /* This is called by the persistent object deallocation function
+       when the reference count on a persistent object reaches
+       zero. We need to fix up our dictionary; its reference is now
+       dangling because we stole its reference count. Be careful to
+       not release the global interpreter lock until this is
+       complete. */
+
+    PyObject *v;
 
     v = PyDict_GetItem(self->data, oid);
     if (v == NULL) {
 	PyErr_SetObject(PyExc_KeyError, oid);
-	/* jeremy debug
-	   fprintf(stderr, "oid_unreferenced: key error\n");
-	*/
-	return NULL;
-    }
-
-    /* jeremy debug
-    fprintf(stderr, "oid_unreferenced: %X %d %s\n", v,
-	    v->ob_refcnt, v->ob_type->tp_name);
-    */
-
-    if (v->ob_refcnt) {
-        PyErr_Format(PyExc_ValueError,
-	     "object has reference count of %d, should be zero", v->ob_refcnt);
-        return NULL;
+	return -1;
     }
 
+    assert(v->ob_refcnt == 0);
     /* Need to be very hairy here because a dictionary is about
        to decref an already deleted object. 
     */
@@ -609,40 +603,33 @@ cc_oid_unreferenced(ccobject *self, PyObject *args)
 #else
     Py_INCREF(v);
 #endif
-
-    if (v->ob_refcnt != 1) {
-        PyErr_SetString(PyExc_ValueError,
-			"refcount is not 1 after resurrection");
-        return NULL;
-    }
-
-    /* return the stolen reference */
+    /* Incremement the refcount again, because delitem is going to
+       DECREF it.  If it's refcount reached zero again, we'd call back to
+       the dealloc function that called us.
+    */
     Py_INCREF(v);
 
+    /* XXX what if this fails? */
     PyDict_DelItem(self->data, oid);
 
     if (v->ob_refcnt != 1) {
         PyErr_SetString(PyExc_ValueError,
 			"refcount is not 1 after removal from dict");
-        return NULL;
+        return -1;
     }
 
     /* undo the temporary resurrection */
 #ifdef Py_TRACE_REFS
     _Py_ForgetReference(v);
 #else
-    v->ob_refcnt=0;
+    v->ob_refcnt = 0;
 #endif
 
-    Py_INCREF(Py_None);
-    return Py_None;
+    return 0;
 }
 
 
 static struct PyMethodDef cc_methods[] = {
-  {"_oid_unreferenced", (PyCFunction)cc_oid_unreferenced, METH_VARARGS,
-   NULL
-   },
   {"lru_items", (PyCFunction)cc_lru_items, METH_VARARGS,
    "List (oid, object) pairs from the lru list, as 2-tuples.\n"
    },
@@ -1103,10 +1090,17 @@ void
 initcPickleCache(void)
 {
   PyObject *m, *d;
+  cPersistenceCAPIstruct *capi;
+
+  Cctype.ob_type = &PyType_Type;
 
-  Cctype.ob_type=&PyType_Type;
+  if (!ExtensionClassImported) 
+      return;
 
-  UNLESS(ExtensionClassImported) return;
+  capi = (cPersistenceCAPIstruct *)PyCObject_Import("cPersistence", "CAPI");
+  if (!capi)
+      return;
+  capi->percachedel = (percachedelfunc)cc_oid_unreferenced;
 
   m = Py_InitModule4("cPickleCache", cCM_methods, cPickleCache_doc_string,
 		     (PyObject*)NULL, PYTHON_API_VERSION);
@@ -1118,11 +1112,11 @@ initcPickleCache(void)
 
   d = PyModule_GetDict(m);
 
-  PyDict_SetItemString(d,"cache_variant",PyString_FromString("stiff/c"));
+  PyDict_SetItemString(d, "cache_variant", PyString_FromString("stiff/c"));
 
 #ifdef MUCH_RING_CHECKING
-  PyDict_SetItemString(d,"MUCH_RING_CHECKING",PyInt_FromLong(1));
+  PyDict_SetItemString(d, "MUCH_RING_CHECKING", PyInt_FromLong(1));
 #else
-  PyDict_SetItemString(d,"MUCH_RING_CHECKING",PyInt_FromLong(0));
+  PyDict_SetItemString(d, "MUCH_RING_CHECKING", PyInt_FromLong(0));
 #endif
 }

src/ZODB/cPersistence.c

@@ -14,11 +14,10 @@
 static char cPersistence_doc_string[] = 
 "Defines Persistent mixin class for persistent objects.\n"
 "\n"
-"$Id: cPersistence.c,v 1.57 2002/04/02 22:46:48 jeremy Exp $\n";
+"$Id: cPersistence.c,v 1.58 2002/04/05 01:12:48 jeremy Exp $\n";
 
 #include "cPersistence.h"
 
-/* XXX What is this structure used for? */
 struct ccobject_head_struct {
     CACHE_HEAD
 };
@@ -202,15 +201,11 @@ deallocated(cPersistentObject *self)
     if (self->state >= 0) 
 	ghostify(self);
     if (self->cache) {
-        PyObject *v;
-
-	/* XXX should just add this to the C API struct */
-	v = PyObject_CallMethod((PyObject *)self->cache, 
-				"_oid_unreferenced", "O", self->oid);
-        if (v == NULL)
-	    PyErr_Clear(); /* I dont think this should ever happen */
-	else
-	    Py_DECREF(v);
+	/* XXX This function shouldn't be able to fail? If not, maybe
+	   it shouldn't set an exception either.
+	*/
+	if (cPersistenceCAPI->percachedel(self->cache, self->oid) < 0)
+	    PyErr_Clear(); /* I don't think this should ever happen */
     }
     Py_XDECREF(self->jar);
     Py_XDECREF(self->oid);
@@ -256,19 +251,22 @@ changed(cPersistentObject *self)
 static PyObject *
 Per___changed__(cPersistentObject *self, PyObject *args)
 {
-  PyObject *v=0;
+    PyObject *v = NULL;
 
-  if (args && ! PyArg_ParseTuple(args, "|O",&v)) return NULL;
-  if (! v) return PyObject_GetAttr(OBJECT(self), py__p_changed);
+    if (args && !PyArg_ParseTuple(args, "|O:__changed__", &v)) 
+	return NULL;
+    if (!v) 
+	return PyObject_GetAttr(OBJECT(self), py__p_changed);
 
-  if (PyObject_IsTrue(v)) 
-    {
-      if (changed(self) < 0) return NULL;
+    if (PyObject_IsTrue(v)) {
+	if (changed(self) < 0) 
+	    return NULL;
     }
-  else if (self->state >= 0) self->state=cPersistent_UPTODATE_STATE;
+    else if (self->state >= 0) 
+	self->state = cPersistent_UPTODATE_STATE;
 
-  Py_INCREF(Py_None);
-  return Py_None;
+    Py_INCREF(Py_None);
+    return Py_None;
 }
 
 static PyObject *
@@ -295,7 +293,7 @@ Per__p_deactivate(cPersistentObject *self, PyObject *args)
     }
 
   /* need to delay releasing the last reference on instance attributes
-  until after we have finished accounting for losing our state */
+     until after we have finished accounting for losing our state */
   if (dict2)
   {
       PyDict_Clear(dict2);
@@ -807,6 +805,7 @@ truecPersistenceCAPI = {
   deallocated,
   (intfunctionwithpythonarg)Per_setstate,
   (pergetattr)Per_getattr,
+  NULL
 };
 
 void
@@ -826,7 +825,8 @@ initcPersistence(void)
   Py_DECREF(m);
   Py_DECREF(s);
 
-  if (init_strings() < 0) return;
+  if (init_strings() < 0) 
+      return;
 
   m = Py_InitModule4("cPersistence", cP_methods, cPersistence_doc_string,
 		     (PyObject*)NULL, PYTHON_API_VERSION);
@@ -837,12 +837,8 @@ initcPersistence(void)
   PyExtensionClass_Export(d, "Persistent",  Pertype);
   PyExtensionClass_Export(d, "Overridable", Overridable);
 
-  cPersistenceCAPI=&truecPersistenceCAPI;
-  s = PyCObject_FromVoidPtr(cPersistenceCAPI,NULL);
+  cPersistenceCAPI = &truecPersistenceCAPI;
+  s = PyCObject_FromVoidPtr(cPersistenceCAPI, NULL);
   PyDict_SetItemString(d, "CAPI", s);
   Py_XDECREF(s);
-
-  /* Check for errors */
-  if (PyErr_Occurred())
-    Py_FatalError("can't initialize module cPersistence");
 }

src/ZODB/cPersistence.h

@@ -18,6 +18,12 @@
 #include "ExtensionClass.h"
 #include <time.h>
 
+typedef struct CPersistentRing_struct
+{
+    struct CPersistentRing_struct *prev;
+    struct CPersistentRing_struct *next;
+} CPersistentRing;
+
 #define CACHE_HEAD \
     PyObject_HEAD \
     CPersistentRing ring_home; \
@@ -42,30 +48,26 @@ typedef struct ccobject_head_struct PerCache;
 #define cPersistent_CHANGED_STATE 1
 #define cPersistent_STICKY_STATE 2
 
-typedef struct CPersistentRing_struct
-{
-    struct CPersistentRing_struct *prev;
-    struct CPersistentRing_struct *next;
-} CPersistentRing;
-
 typedef struct {
     cPersistent_HEAD
 } cPersistentObject;
 
 typedef int (*persetattr)(PyObject *, PyObject*, PyObject *, setattrofunc);
 typedef PyObject *(*pergetattr)(PyObject *, PyObject*, char *, getattrofunc);
+typedef int (*percachedelfunc)(PerCache *, PyObject *);
 
 typedef struct {
-  PyMethodChain *methods;
-  getattrofunc getattro;
-  setattrofunc setattro;
-  int (*changed)(cPersistentObject*);
-  void (*accessed)(cPersistentObject*);
-  void (*ghostify)(cPersistentObject*);
-  void (*deallocated)(cPersistentObject*);
-  int (*setstate)(PyObject*);
-  pergetattr pergetattro;
-  persetattr persetattro;
+    PyMethodChain *methods;
+    getattrofunc getattro;
+    setattrofunc setattro;
+    int (*changed)(cPersistentObject*);
+    void (*accessed)(cPersistentObject*);
+    void (*ghostify)(cPersistentObject*);
+    void (*deallocated)(cPersistentObject*);
+    int (*setstate)(PyObject*);
+    pergetattr pergetattro;
+    persetattr persetattro;
+    percachedelfunc percachedel;
 } cPersistenceCAPIstruct;
 
 #ifndef DONT_USE_CPERSISTENCECAPI

src/ZODB/cPickleCache.c

@@ -88,7 +88,7 @@ process must skip such objects, rather than deactivating them.
 static char cPickleCache_doc_string[] =
 "Defines the PickleCache used by ZODB Connection objects.\n"
 "\n"
-"$Id: cPickleCache.c,v 1.54 2002/04/04 22:02:32 bwarsaw Exp $\n";
+"$Id: cPickleCache.c,v 1.55 2002/04/05 01:12:48 jeremy Exp $\n";
 
 #define ASSIGN(V,E) {PyObject *__e; __e=(E); Py_XDECREF(V); (V)=__e;}
 #define UNLESS(E) if(!(E))
@@ -118,9 +118,9 @@ static PyObject *py__p_oid, *py_reload, *py__p_jar, *py__p_changed;
 #define ENGINE_NOISE(A) ((void)A)
 #endif
 
-/* This object is the pickle cache.  The CACHE_HEAD macro guarantees that
-layout of this struct is the same as the start of ccobject_head in
-cPersistence.c */
+/* This object is the pickle cache.  The CACHE_HEAD macro guarantees
+   that layout of this struct is the same as the start of
+   ccobject_head in cPersistence.c */
 typedef struct {
     CACHE_HEAD
     int klass_count;                         /* count of persistent classes */
@@ -156,15 +156,15 @@ static int cc_ass_sub(ccobject *self, PyObject *key, PyObject *v);
 
 /* ---------------------------------------------------------------- */
 
-static PyObject *object_from_oid(ccobject *self, PyObject *key)
 /* somewhat of a replacement for PyDict_GetItem(self->data....
    however this returns a *new* reference */
+static PyObject *
+object_from_oid(ccobject *self, PyObject *key)
 {
     PyObject *v = PyDict_GetItem(self->data, key);
-    if(!v) return NULL;
-
+    if (!v) 
+	return NULL;
     Py_INCREF(v);
-
     return v;
 }
 
@@ -263,10 +263,11 @@ scan_gc_items(ccobject *self,int target)
         if (here == &self->ring_home)
             return 0;
 
-        /* At this point we know that the ring only contains nodes from
-        persistent objects, plus our own home node. We know this because
-        the ring lock is held.  We can safely assume the current ring
-        node is a persistent object now we know it is not the home */
+        /* At this point we know that the ring only contains nodes
+	   from persistent objects, plus our own home node. We know
+	   this because the ring lock is held.  We can safely assume
+	   the current ring node is a persistent object now we know it
+	   is not the home */
         object = object_from_ring(self, here, "scan_gc_items");
         if (!object) 
 	    return -1;
@@ -277,12 +278,15 @@ scan_gc_items(ccobject *self,int target)
         else if (object->state == cPersistent_UPTODATE_STATE) {
             /* deactivate it. This is the main memory saver. */
 
-            /* Add a placeholder; a dummy node in the ring. We need to
-            do this to mark our position in the ring. All the other nodes
-            come from persistent objects, and they are all liable
-            to be deallocated before "obj._p_changed = None" returns
-            to this function. This operation is only safe when the
-            ring lock is held (and it is) */
+            /* Add a placeholder; a dummy node in the ring.  We need
+	       to do this to mark our position in the ring.  It is
+	       possible that the PyObject_SetAttr() call below will
+	       invoke an __setattr__() hook in Python.  If it does,
+	       another thread might run; if that thread accesses a
+	       persistent object and moves it to the head of the ring,
+	       it might cause the gc scan to start working from the
+	       head of the list.
+	    */
 
             placeholder.next = here->next;
             placeholder.prev = here;
@@ -315,7 +319,7 @@ scan_gc_items(ccobject *self,int target)
 static PyObject *
 lockgc(ccobject *self, int target_size)
 {
-    /* We think this is thread-safe because of the GIL, and there's nothing
+    /* This is thread-safe because of the GIL, and there's nothing
      * in between checking the ring_lock and acquiring it that calls back
      * into Python.
      */
@@ -361,16 +365,23 @@ cc_incrgc(ccobject *self, PyObject *args)
     if (!PyArg_ParseTuple(args, "|i:incrgc", &n)) 
 	return NULL;
 
-    return lockgc(self,target_size);
+    return lockgc(self, target_size);
 }
 
+/* XXX Does it make sense for full_sweep() and reallyfull_sweep() to
+   empty the cache completely?  I agree that it would if dt is 0, but
+   don't think it should for other times.  Perhaps it should just call
+   incrgc() if dt > 2; the new cache may be efficient enough that
+   incrgc() would suffice.
+*/
+
 static PyObject *
 cc_full_sweep(ccobject *self, PyObject *args)
 {
     int dt = 0;
     if (!PyArg_ParseTuple(args, "|i:full_sweep", &dt)) 
 	return NULL;
-    return lockgc(self,0);
+    return lockgc(self, 0);
 }
 
 static PyObject *
@@ -379,7 +390,7 @@ cc_reallyfull_sweep(ccobject *self, PyObject *args)
   int dt = 0;
   if (!PyArg_ParseTuple(args, "|i:reallyfull_sweep", &dt)) 
       return NULL;
-  return lockgc(self,0);
+  return lockgc(self, 0);
 }
 
 static void
@@ -460,22 +471,19 @@ cc_get(ccobject *self, PyObject *args)
 {
   PyObject *r, *key, *d=0;
 
-  UNLESS (PyArg_ParseTuple(args,"O|O", &key, &d)) return NULL;
+  if (!PyArg_ParseTuple(args, "O|O:get", &key, &d)) 
+      return NULL;
 
-  UNLESS (r=(PyObject *)object_from_oid(self, key))
-    {
-      if (d) 
-	{
-	  PyErr_Clear();
-	  r=d;
+  r = (PyObject *)object_from_oid(self, key);
+  if (!r) {
+      if (d) {
+	  r = d;
           Py_INCREF(r);
-	}
-      else
-	{
+      } else {
 	  PyErr_SetObject(PyExc_KeyError, key);
 	  return NULL;
-	}
-    }
+      }
+  }
 
   return r;
 }
@@ -522,8 +530,9 @@ cc_lru_items(ccobject *self, PyObject *args)
 	return NULL;
 
     if (self->ring_lock) {
-	/* When the ring lock is held, we have no way of know which ring nodes
-	belong to persistent objects, and which a placeholders. */
+	/* When the ring lock is held, we have no way of know which
+	   ring nodes belong to persistent objects, and which a
+	   placeholders. */
         PyErr_SetString(PyExc_ValueError,
 		".lru_items() is unavailable during garbage collection");
         return NULL;
@@ -562,40 +571,25 @@ cc_lru_items(ccobject *self, PyObject *args)
     return l;
 }
 
-static PyObject *
-cc_oid_unreferenced(ccobject *self, PyObject *args)
+static int
+cc_oid_unreferenced(ccobject *self, PyObject *oid)
 {
-    /* This is called by the persistent object deallocation
-    function when the reference count on a persistent
-    object reaches zero. We need to fix up our dictionary;
-    its reference is now dangling because we stole its
-    reference count. Be careful to not release the global
-    interpreter lock until this is complete. */
-
-    PyObject *oid, *v;
-    if (!PyArg_ParseTuple(args, "O:_oid_unreferenced", &oid)) 
-	return NULL;
+    /* This is called by the persistent object deallocation function
+       when the reference count on a persistent object reaches
+       zero. We need to fix up our dictionary; its reference is now
+       dangling because we stole its reference count. Be careful to
+       not release the global interpreter lock until this is
+       complete. */
+
+    PyObject *v;
 
     v = PyDict_GetItem(self->data, oid);
     if (v == NULL) {
 	PyErr_SetObject(PyExc_KeyError, oid);
-	/* jeremy debug
-	   fprintf(stderr, "oid_unreferenced: key error\n");
-	*/
-	return NULL;
-    }
-
-    /* jeremy debug
-    fprintf(stderr, "oid_unreferenced: %X %d %s\n", v,
-	    v->ob_refcnt, v->ob_type->tp_name);
-    */
-
-    if (v->ob_refcnt) {
-        PyErr_Format(PyExc_ValueError,
-	     "object has reference count of %d, should be zero", v->ob_refcnt);
-        return NULL;
+	return -1;
     }
 
+    assert(v->ob_refcnt == 0);
     /* Need to be very hairy here because a dictionary is about
        to decref an already deleted object. 
     */
@@ -609,40 +603,33 @@ cc_oid_unreferenced(ccobject *self, PyObject *args)
 #else
     Py_INCREF(v);
 #endif
-
-    if (v->ob_refcnt != 1) {
-        PyErr_SetString(PyExc_ValueError,
-			"refcount is not 1 after resurrection");
-        return NULL;
-    }
-
-    /* return the stolen reference */
+    /* Incremement the refcount again, because delitem is going to
+       DECREF it.  If it's refcount reached zero again, we'd call back to
+       the dealloc function that called us.
+    */
     Py_INCREF(v);
 
+    /* XXX what if this fails? */
     PyDict_DelItem(self->data, oid);
 
     if (v->ob_refcnt != 1) {
         PyErr_SetString(PyExc_ValueError,
 			"refcount is not 1 after removal from dict");
-        return NULL;
+        return -1;
     }
 
     /* undo the temporary resurrection */
 #ifdef Py_TRACE_REFS
     _Py_ForgetReference(v);
 #else
-    v->ob_refcnt=0;
+    v->ob_refcnt = 0;
 #endif
 
-    Py_INCREF(Py_None);
-    return Py_None;
+    return 0;
 }
 
 
 static struct PyMethodDef cc_methods[] = {
-  {"_oid_unreferenced", (PyCFunction)cc_oid_unreferenced, METH_VARARGS,
-   NULL
-   },
   {"lru_items", (PyCFunction)cc_lru_items, METH_VARARGS,
    "List (oid, object) pairs from the lru list, as 2-tuples.\n"
    },
@@ -1103,10 +1090,17 @@ void
 initcPickleCache(void)
 {
   PyObject *m, *d;
+  cPersistenceCAPIstruct *capi;
+
+  Cctype.ob_type = &PyType_Type;
 
-  Cctype.ob_type=&PyType_Type;
+  if (!ExtensionClassImported) 
+      return;
 
-  UNLESS(ExtensionClassImported) return;
+  capi = (cPersistenceCAPIstruct *)PyCObject_Import("cPersistence", "CAPI");
+  if (!capi)
+      return;
+  capi->percachedel = (percachedelfunc)cc_oid_unreferenced;
 
   m = Py_InitModule4("cPickleCache", cCM_methods, cPickleCache_doc_string,
 		     (PyObject*)NULL, PYTHON_API_VERSION);
@@ -1118,11 +1112,11 @@ initcPickleCache(void)
 
   d = PyModule_GetDict(m);
 
-  PyDict_SetItemString(d,"cache_variant",PyString_FromString("stiff/c"));
+  PyDict_SetItemString(d, "cache_variant", PyString_FromString("stiff/c"));
 
 #ifdef MUCH_RING_CHECKING
-  PyDict_SetItemString(d,"MUCH_RING_CHECKING",PyInt_FromLong(1));
+  PyDict_SetItemString(d, "MUCH_RING_CHECKING", PyInt_FromLong(1));
 #else
-  PyDict_SetItemString(d,"MUCH_RING_CHECKING",PyInt_FromLong(0));
+  PyDict_SetItemString(d, "MUCH_RING_CHECKING", PyInt_FromLong(0));
 #endif
 }

src/persistent/cPersistence.c

@@ -14,11 +14,10 @@
 static char cPersistence_doc_string[] = 
 "Defines Persistent mixin class for persistent objects.\n"
 "\n"
-"$Id: cPersistence.c,v 1.57 2002/04/02 22:46:48 jeremy Exp $\n";
+"$Id: cPersistence.c,v 1.58 2002/04/05 01:12:48 jeremy Exp $\n";
 
 #include "cPersistence.h"
 
-/* XXX What is this structure used for? */
 struct ccobject_head_struct {
     CACHE_HEAD
 };
@@ -202,15 +201,11 @@ deallocated(cPersistentObject *self)
     if (self->state >= 0) 
 	ghostify(self);
     if (self->cache) {
-        PyObject *v;
-
-	/* XXX should just add this to the C API struct */
-	v = PyObject_CallMethod((PyObject *)self->cache, 
-				"_oid_unreferenced", "O", self->oid);
-        if (v == NULL)
-	    PyErr_Clear(); /* I dont think this should ever happen */
-	else
-	    Py_DECREF(v);
+	/* XXX This function shouldn't be able to fail? If not, maybe
+	   it shouldn't set an exception either.
+	*/
+	if (cPersistenceCAPI->percachedel(self->cache, self->oid) < 0)
+	    PyErr_Clear(); /* I don't think this should ever happen */
     }
     Py_XDECREF(self->jar);
     Py_XDECREF(self->oid);
@@ -256,19 +251,22 @@ changed(cPersistentObject *self)
 static PyObject *
 Per___changed__(cPersistentObject *self, PyObject *args)
 {
-  PyObject *v=0;
+    PyObject *v = NULL;
 
-  if (args && ! PyArg_ParseTuple(args, "|O",&v)) return NULL;
-  if (! v) return PyObject_GetAttr(OBJECT(self), py__p_changed);
+    if (args && !PyArg_ParseTuple(args, "|O:__changed__", &v)) 
+	return NULL;
+    if (!v) 
+	return PyObject_GetAttr(OBJECT(self), py__p_changed);
 
-  if (PyObject_IsTrue(v)) 
-    {
-      if (changed(self) < 0) return NULL;
+    if (PyObject_IsTrue(v)) {
+	if (changed(self) < 0) 
+	    return NULL;
     }
-  else if (self->state >= 0) self->state=cPersistent_UPTODATE_STATE;
+    else if (self->state >= 0) 
+	self->state = cPersistent_UPTODATE_STATE;
 
-  Py_INCREF(Py_None);
-  return Py_None;
+    Py_INCREF(Py_None);
+    return Py_None;
 }
 
 static PyObject *
@@ -295,7 +293,7 @@ Per__p_deactivate(cPersistentObject *self, PyObject *args)
     }
 
   /* need to delay releasing the last reference on instance attributes
-  until after we have finished accounting for losing our state */
+     until after we have finished accounting for losing our state */
   if (dict2)
   {
       PyDict_Clear(dict2);
@@ -807,6 +805,7 @@ truecPersistenceCAPI = {
   deallocated,
   (intfunctionwithpythonarg)Per_setstate,
   (pergetattr)Per_getattr,
+  NULL
 };
 
 void
@@ -826,7 +825,8 @@ initcPersistence(void)
   Py_DECREF(m);
   Py_DECREF(s);
 
-  if (init_strings() < 0) return;
+  if (init_strings() < 0) 
+      return;
 
   m = Py_InitModule4("cPersistence", cP_methods, cPersistence_doc_string,
 		     (PyObject*)NULL, PYTHON_API_VERSION);
@@ -837,12 +837,8 @@ initcPersistence(void)
   PyExtensionClass_Export(d, "Persistent",  Pertype);
   PyExtensionClass_Export(d, "Overridable", Overridable);
 
-  cPersistenceCAPI=&truecPersistenceCAPI;
-  s = PyCObject_FromVoidPtr(cPersistenceCAPI,NULL);
+  cPersistenceCAPI = &truecPersistenceCAPI;
+  s = PyCObject_FromVoidPtr(cPersistenceCAPI, NULL);
   PyDict_SetItemString(d, "CAPI", s);
   Py_XDECREF(s);
-
-  /* Check for errors */
-  if (PyErr_Occurred())
-    Py_FatalError("can't initialize module cPersistence");
 }

src/persistent/cPersistence.h

@@ -18,6 +18,12 @@
 #include "ExtensionClass.h"
 #include <time.h>
 
+typedef struct CPersistentRing_struct
+{
+    struct CPersistentRing_struct *prev;
+    struct CPersistentRing_struct *next;
+} CPersistentRing;
+
 #define CACHE_HEAD \
     PyObject_HEAD \
     CPersistentRing ring_home; \
@@ -42,30 +48,26 @@ typedef struct ccobject_head_struct PerCache;
 #define cPersistent_CHANGED_STATE 1
 #define cPersistent_STICKY_STATE 2
 
-typedef struct CPersistentRing_struct
-{
-    struct CPersistentRing_struct *prev;
-    struct CPersistentRing_struct *next;
-} CPersistentRing;
-
 typedef struct {
     cPersistent_HEAD
 } cPersistentObject;
 
 typedef int (*persetattr)(PyObject *, PyObject*, PyObject *, setattrofunc);
 typedef PyObject *(*pergetattr)(PyObject *, PyObject*, char *, getattrofunc);
+typedef int (*percachedelfunc)(PerCache *, PyObject *);
 
 typedef struct {
-  PyMethodChain *methods;
-  getattrofunc getattro;
-  setattrofunc setattro;
-  int (*changed)(cPersistentObject*);
-  void (*accessed)(cPersistentObject*);
-  void (*ghostify)(cPersistentObject*);
-  void (*deallocated)(cPersistentObject*);
-  int (*setstate)(PyObject*);
-  pergetattr pergetattro;
-  persetattr persetattro;
+    PyMethodChain *methods;
+    getattrofunc getattro;
+    setattrofunc setattro;
+    int (*changed)(cPersistentObject*);
+    void (*accessed)(cPersistentObject*);
+    void (*ghostify)(cPersistentObject*);
+    void (*deallocated)(cPersistentObject*);
+    int (*setstate)(PyObject*);
+    pergetattr pergetattro;
+    persetattr persetattro;
+    percachedelfunc percachedel;
 } cPersistenceCAPIstruct;
 
 #ifndef DONT_USE_CPERSISTENCECAPI

src/persistent/cPickleCache.c

@@ -88,7 +88,7 @@ process must skip such objects, rather than deactivating them.
 static char cPickleCache_doc_string[] =
 "Defines the PickleCache used by ZODB Connection objects.\n"
 "\n"
-"$Id: cPickleCache.c,v 1.54 2002/04/04 22:02:32 bwarsaw Exp $\n";
+"$Id: cPickleCache.c,v 1.55 2002/04/05 01:12:48 jeremy Exp $\n";
 
 #define ASSIGN(V,E) {PyObject *__e; __e=(E); Py_XDECREF(V); (V)=__e;}
 #define UNLESS(E) if(!(E))
@@ -118,9 +118,9 @@ static PyObject *py__p_oid, *py_reload, *py__p_jar, *py__p_changed;
 #define ENGINE_NOISE(A) ((void)A)
 #endif
 
-/* This object is the pickle cache.  The CACHE_HEAD macro guarantees that
-layout of this struct is the same as the start of ccobject_head in
-cPersistence.c */
+/* This object is the pickle cache.  The CACHE_HEAD macro guarantees
+   that layout of this struct is the same as the start of
+   ccobject_head in cPersistence.c */
 typedef struct {
     CACHE_HEAD
     int klass_count;                         /* count of persistent classes */
@@ -156,15 +156,15 @@ static int cc_ass_sub(ccobject *self, PyObject *key, PyObject *v);
 
 /* ---------------------------------------------------------------- */
 
-static PyObject *object_from_oid(ccobject *self, PyObject *key)
 /* somewhat of a replacement for PyDict_GetItem(self->data....
    however this returns a *new* reference */
+static PyObject *
+object_from_oid(ccobject *self, PyObject *key)
 {
     PyObject *v = PyDict_GetItem(self->data, key);
-    if(!v) return NULL;
-
+    if (!v) 
+	return NULL;
     Py_INCREF(v);
-
     return v;
 }
 
@@ -263,10 +263,11 @@ scan_gc_items(ccobject *self,int target)
         if (here == &self->ring_home)
             return 0;
 
-        /* At this point we know that the ring only contains nodes from
-        persistent objects, plus our own home node. We know this because
-        the ring lock is held.  We can safely assume the current ring
-        node is a persistent object now we know it is not the home */
+        /* At this point we know that the ring only contains nodes
+	   from persistent objects, plus our own home node. We know
+	   this because the ring lock is held.  We can safely assume
+	   the current ring node is a persistent object now we know it
+	   is not the home */
         object = object_from_ring(self, here, "scan_gc_items");
         if (!object) 
 	    return -1;
@@ -277,12 +278,15 @@ scan_gc_items(ccobject *self,int target)
         else if (object->state == cPersistent_UPTODATE_STATE) {
             /* deactivate it. This is the main memory saver. */
 
-            /* Add a placeholder; a dummy node in the ring. We need to
-            do this to mark our position in the ring. All the other nodes
-            come from persistent objects, and they are all liable
-            to be deallocated before "obj._p_changed = None" returns
-            to this function. This operation is only safe when the
-            ring lock is held (and it is) */
+            /* Add a placeholder; a dummy node in the ring.  We need
+	       to do this to mark our position in the ring.  It is
+	       possible that the PyObject_SetAttr() call below will
+	       invoke an __setattr__() hook in Python.  If it does,
+	       another thread might run; if that thread accesses a
+	       persistent object and moves it to the head of the ring,
+	       it might cause the gc scan to start working from the
+	       head of the list.
+	    */
 
             placeholder.next = here->next;
             placeholder.prev = here;
@@ -315,7 +319,7 @@ scan_gc_items(ccobject *self,int target)
 static PyObject *
 lockgc(ccobject *self, int target_size)
 {
-    /* We think this is thread-safe because of the GIL, and there's nothing
+    /* This is thread-safe because of the GIL, and there's nothing
      * in between checking the ring_lock and acquiring it that calls back
      * into Python.
      */
@@ -361,16 +365,23 @@ cc_incrgc(ccobject *self, PyObject *args)
     if (!PyArg_ParseTuple(args, "|i:incrgc", &n)) 
 	return NULL;
 
-    return lockgc(self,target_size);
+    return lockgc(self, target_size);
 }
 
+/* XXX Does it make sense for full_sweep() and reallyfull_sweep() to
+   empty the cache completely?  I agree that it would if dt is 0, but
+   don't think it should for other times.  Perhaps it should just call
+   incrgc() if dt > 2; the new cache may be efficient enough that
+   incrgc() would suffice.
+*/
+
 static PyObject *
 cc_full_sweep(ccobject *self, PyObject *args)
 {
     int dt = 0;
     if (!PyArg_ParseTuple(args, "|i:full_sweep", &dt)) 
 	return NULL;
-    return lockgc(self,0);
+    return lockgc(self, 0);
 }
 
 static PyObject *
@@ -379,7 +390,7 @@ cc_reallyfull_sweep(ccobject *self, PyObject *args)
   int dt = 0;
   if (!PyArg_ParseTuple(args, "|i:reallyfull_sweep", &dt)) 
       return NULL;
-  return lockgc(self,0);
+  return lockgc(self, 0);
 }
 
 static void
@@ -460,22 +471,19 @@ cc_get(ccobject *self, PyObject *args)
 {
   PyObject *r, *key, *d=0;
 
-  UNLESS (PyArg_ParseTuple(args,"O|O", &key, &d)) return NULL;
+  if (!PyArg_ParseTuple(args, "O|O:get", &key, &d)) 
+      return NULL;
 
-  UNLESS (r=(PyObject *)object_from_oid(self, key))
-    {
-      if (d) 
-	{
-	  PyErr_Clear();
-	  r=d;
+  r = (PyObject *)object_from_oid(self, key);
+  if (!r) {
+      if (d) {
+	  r = d;
           Py_INCREF(r);
-	}
-      else
-	{
+      } else {
 	  PyErr_SetObject(PyExc_KeyError, key);
 	  return NULL;
-	}
-    }
+      }
+  }
 
   return r;
 }
@@ -522,8 +530,9 @@ cc_lru_items(ccobject *self, PyObject *args)
 	return NULL;
 
     if (self->ring_lock) {
-	/* When the ring lock is held, we have no way of know which ring nodes
-	belong to persistent objects, and which a placeholders. */
+	/* When the ring lock is held, we have no way of know which
+	   ring nodes belong to persistent objects, and which a
+	   placeholders. */
         PyErr_SetString(PyExc_ValueError,
 		".lru_items() is unavailable during garbage collection");
         return NULL;
@@ -562,40 +571,25 @@ cc_lru_items(ccobject *self, PyObject *args)
     return l;
 }
 
-static PyObject *
-cc_oid_unreferenced(ccobject *self, PyObject *args)
+static int
+cc_oid_unreferenced(ccobject *self, PyObject *oid)
 {
-    /* This is called by the persistent object deallocation
-    function when the reference count on a persistent
-    object reaches zero. We need to fix up our dictionary;
-    its reference is now dangling because we stole its
-    reference count. Be careful to not release the global
-    interpreter lock until this is complete. */
-
-    PyObject *oid, *v;
-    if (!PyArg_ParseTuple(args, "O:_oid_unreferenced", &oid)) 
-	return NULL;
+    /* This is called by the persistent object deallocation function
+       when the reference count on a persistent object reaches
+       zero. We need to fix up our dictionary; its reference is now
+       dangling because we stole its reference count. Be careful to
+       not release the global interpreter lock until this is
+       complete. */
+
+    PyObject *v;
 
     v = PyDict_GetItem(self->data, oid);
     if (v == NULL) {
 	PyErr_SetObject(PyExc_KeyError, oid);
-	/* jeremy debug
-	   fprintf(stderr, "oid_unreferenced: key error\n");
-	*/
-	return NULL;
-    }
-
-    /* jeremy debug
-    fprintf(stderr, "oid_unreferenced: %X %d %s\n", v,
-	    v->ob_refcnt, v->ob_type->tp_name);
-    */
-
-    if (v->ob_refcnt) {
-        PyErr_Format(PyExc_ValueError,
-	     "object has reference count of %d, should be zero", v->ob_refcnt);
-        return NULL;
+	return -1;
     }
 
+    assert(v->ob_refcnt == 0);
     /* Need to be very hairy here because a dictionary is about
        to decref an already deleted object. 
     */
@@ -609,40 +603,33 @@ cc_oid_unreferenced(ccobject *self, PyObject *args)
 #else
     Py_INCREF(v);
 #endif
-
-    if (v->ob_refcnt != 1) {
-        PyErr_SetString(PyExc_ValueError,
-			"refcount is not 1 after resurrection");
-        return NULL;
-    }
-
-    /* return the stolen reference */
+    /* Incremement the refcount again, because delitem is going to
+       DECREF it.  If it's refcount reached zero again, we'd call back to
+       the dealloc function that called us.
+    */
     Py_INCREF(v);
 
+    /* XXX what if this fails? */
     PyDict_DelItem(self->data, oid);
 
     if (v->ob_refcnt != 1) {
         PyErr_SetString(PyExc_ValueError,
 			"refcount is not 1 after removal from dict");
-        return NULL;
+        return -1;
     }
 
     /* undo the temporary resurrection */
 #ifdef Py_TRACE_REFS
     _Py_ForgetReference(v);
 #else
-    v->ob_refcnt=0;
+    v->ob_refcnt = 0;
 #endif
 
-    Py_INCREF(Py_None);
-    return Py_None;
+    return 0;
 }
 
 
 static struct PyMethodDef cc_methods[] = {
-  {"_oid_unreferenced", (PyCFunction)cc_oid_unreferenced, METH_VARARGS,
-   NULL
-   },
   {"lru_items", (PyCFunction)cc_lru_items, METH_VARARGS,
    "List (oid, object) pairs from the lru list, as 2-tuples.\n"
    },
@@ -1103,10 +1090,17 @@ void
 initcPickleCache(void)
 {
   PyObject *m, *d;
+  cPersistenceCAPIstruct *capi;
+
+  Cctype.ob_type = &PyType_Type;
 
-  Cctype.ob_type=&PyType_Type;
+  if (!ExtensionClassImported) 
+      return;
 
-  UNLESS(ExtensionClassImported) return;
+  capi = (cPersistenceCAPIstruct *)PyCObject_Import("cPersistence", "CAPI");
+  if (!capi)
+      return;
+  capi->percachedel = (percachedelfunc)cc_oid_unreferenced;
 
   m = Py_InitModule4("cPickleCache", cCM_methods, cPickleCache_doc_string,
 		     (PyObject*)NULL, PYTHON_API_VERSION);
@@ -1118,11 +1112,11 @@ initcPickleCache(void)
 
   d = PyModule_GetDict(m);
 
-  PyDict_SetItemString(d,"cache_variant",PyString_FromString("stiff/c"));
+  PyDict_SetItemString(d, "cache_variant", PyString_FromString("stiff/c"));
 
 #ifdef MUCH_RING_CHECKING
-  PyDict_SetItemString(d,"MUCH_RING_CHECKING",PyInt_FromLong(1));
+  PyDict_SetItemString(d, "MUCH_RING_CHECKING", PyInt_FromLong(1));
 #else
-  PyDict_SetItemString(d,"MUCH_RING_CHECKING",PyInt_FromLong(0));
+  PyDict_SetItemString(d, "MUCH_RING_CHECKING", PyInt_FromLong(0));
 #endif
 }