Variety of small INC/DECREF patches that fix reported memory leaks

with free variables.  Thanks to Martin v. Loewis for finding two of
the problems.  This fixes SF buf 405583.

There is also a C API change: PyFrame_New() is reverting to its
pre-2.1 signature.  The change introduced by nested scopes was a
mistake.  XXX Is this okay between beta releases?

cell_clear(), the GC helper, must decref its reference to break
cycles.

frame_dealloc() must dealloc all cell vars and free vars in addition
to locals.

eval_code2() setup code must INCREF cells it copies out of the
closure.

The STORE_DEREF opcode implementation must DECREF the object it passes
to PyCell_Set().

Include/frameobject.h

@@ -46,8 +46,7 @@ extern DL_IMPORT(PyTypeObject) PyFrame_Type;
 #define PyFrame_Check(op) ((op)->ob_type == &PyFrame_Type)
 
 DL_IMPORT(PyFrameObject *) PyFrame_New(PyThreadState *, PyCodeObject *,
-                                       PyObject *, PyObject *,
-				       PyObject *);
+                                       PyObject *, PyObject *);
 
 
 /* The rest of the interface is specific for frame objects */

Modules/pyexpat.c

@@ -356,9 +356,6 @@ call_with_frame(PyCodeObject *c, PyObject* func, PyObject* args)
                     c,				/*code*/
                     tstate->frame->f_globals,	/*globals*/
                     NULL			/*locals*/
-#if PYTHON_API_VERSION >= 1010
-                    ,NULL			/*closure*/
-#endif
                     );
     if (f == NULL)
         return NULL;

Objects/cellobject.c

@@ -83,6 +83,7 @@ cell_traverse(PyCellObject *op, visitproc visit, void *arg)
 static int
 cell_clear(PyCellObject *op)
 {
+	Py_XDECREF(op->ob_ref);
 	op->ob_ref = NULL;
 	return 0;
 }

Objects/frameobject.c

@@ -65,13 +65,14 @@ static PyFrameObject *free_list = NULL;
 static void
 frame_dealloc(PyFrameObject *f)
 {
-	int i;
+	int i, slots;
 	PyObject **fastlocals;
 
 	Py_TRASHCAN_SAFE_BEGIN(f)
 	/* Kill all local variables */
+	slots = f->f_nlocals + f->f_ncells + f->f_nfreevars;
 	fastlocals = f->f_localsplus;
-	for (i = f->f_nlocals; --i >= 0; ++fastlocals) {
+	for (i = slots; --i >= 0; ++fastlocals) {
 		Py_XDECREF(*fastlocals);
 	}
 
@@ -108,7 +109,7 @@ PyTypeObject PyFrame_Type = {
 
 PyFrameObject *
 PyFrame_New(PyThreadState *tstate, PyCodeObject *code, PyObject *globals, 
-	    PyObject *locals, PyObject *closure)
+	    PyObject *locals)
 {
 	PyFrameObject *back = tstate->frame;
 	static PyObject *builtin_object;

Python/ceval.c

@@ -430,7 +430,7 @@ eval_code2(PyCodeObject *co, PyObject *globals, PyObject *locals,
 
 	f = PyFrame_New(tstate,			/*back*/
 			co,			/*code*/
-			globals, locals, closure);
+			globals, locals);
 	if (f == NULL)
 		return NULL;
 
@@ -578,8 +578,11 @@ eval_code2(PyCodeObject *co, PyObject *globals, PyObject *locals,
 	}
 	if (f->f_nfreevars) {
 		int i;
-		for (i = 0; i < f->f_nfreevars; ++i)
-			freevars[f->f_ncells + i] = PyTuple_GET_ITEM(closure, i);
+		for (i = 0; i < f->f_nfreevars; ++i) {
+			PyObject *o = PyTuple_GET_ITEM(closure, i);
+			Py_INCREF(o);
+			freevars[f->f_ncells + i] = o;
+		}
 	}
 
 	if (tstate->sys_tracefunc != NULL) {
@@ -1662,7 +1665,6 @@ eval_code2(PyCodeObject *co, PyObject *globals, PyObject *locals,
 				err = -1;
 				break;
 			}
-			Py_INCREF(w);
 			PUSH(w);
 			break;
 
@@ -1670,6 +1672,7 @@ eval_code2(PyCodeObject *co, PyObject *globals, PyObject *locals,
 			w = POP();
 			x = freevars[oparg];
 			PyCell_Set(x, w);
+			Py_DECREF(w);
 			continue;
 
 		case BUILD_TUPLE: