Backout c89febab4648 following private feedback by Guido.

pitrou · pitrou · commit 93963569487b · 2013-05-14T20:37:52.000+02:00
(Issue #17807: Generators can now be finalized even when they are part of a reference cycle)
diff --git a/Include/frameobject.h b/Include/frameobject.h
@@ -36,8 +36,6 @@ typedef struct _frame {
            non-generator frames. See the save_exc_state and swap_exc_state
            functions in ceval.c for details of their use. */
     PyObject *f_exc_type, *f_exc_value, *f_exc_traceback;
-    /* Borrowed referenced to a generator, or NULL */
-    PyObject *f_gen;
 
     PyThreadState *f_tstate;
     int f_lasti;                /* Last instruction if called */
@@ -86,13 +84,6 @@ PyAPI_FUNC(void) _PyFrame_DebugMallocStats(FILE *out);
 /* Return the line of code the frame is currently executing. */
 PyAPI_FUNC(int) PyFrame_GetLineNumber(PyFrameObject *);
 
-/* Generator support */
-PyAPI_FUNC(PyObject *) _PyFrame_YieldingFrom(PyFrameObject *);
-PyAPI_FUNC(PyObject *) _PyFrame_GeneratorSend(PyFrameObject *, PyObject *, int exc);
-PyAPI_FUNC(PyObject *) _PyFrame_Finalize(PyFrameObject *);
-PyAPI_FUNC(int) _PyFrame_CloseIterator(PyObject *);
-
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/Include/genobject.h b/Include/genobject.h
@@ -33,7 +33,6 @@ PyAPI_DATA(PyTypeObject) PyGen_Type;
 #define PyGen_CheckExact(op) (Py_TYPE(op) == &PyGen_Type)
 
 PyAPI_FUNC(PyObject *) PyGen_New(struct _frame *);
-/* Deprecated, kept for backwards compatibility. */
 PyAPI_FUNC(int) PyGen_NeedsFinalizing(PyGenObject *);
 PyAPI_FUNC(int) _PyGen_FetchStopIterationValue(PyObject **);
 PyObject *_PyGen_Send(PyGenObject *, PyObject *);
diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
@@ -1,55 +1,3 @@
-import gc
-import sys
-import unittest
-import weakref
-
-from test import support
-
-
-class FinalizationTest(unittest.TestCase):
-
-    def test_frame_resurrect(self):
-        # A generator frame can be resurrected by a generator's finalization.
-        def gen():
-            nonlocal frame
-            try:
-                yield
-            finally:
-                frame = sys._getframe()
-
-        g = gen()
-        wr = weakref.ref(g)
-        next(g)
-        del g
-        support.gc_collect()
-        self.assertIs(wr(), None)
-        self.assertTrue(frame)
-        del frame
-        support.gc_collect()
-
-    def test_refcycle(self):
-        # A generator caught in a refcycle gets finalized anyway.
-        old_garbage = gc.garbage[:]
-        finalized = False
-        def gen():
-            nonlocal finalized
-            try:
-                g = yield
-                yield 1
-            finally:
-                finalized = True
-
-        g = gen()
-        next(g)
-        g.send(g)
-        self.assertGreater(sys.getrefcount(g), 2)
-        self.assertFalse(finalized)
-        del g
-        support.gc_collect()
-        self.assertTrue(finalized)
-        self.assertEqual(gc.garbage, old_garbage)
-
-
 tutorial_tests = """
 Let's try a simple generator:
 
@@ -1932,7 +1880,6 @@ def printsolution(self, x):
 # so this works as expected in both ways of running regrtest.
 def test_main(verbose=None):
     from test import support, test_generators
-    support.run_unittest(__name__)
     support.run_doctest(test_generators, verbose)
 
 # This part isn't needed for regrtest, but for running the test directly.
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
@@ -764,7 +764,7 @@ class C(object): pass
         nfrees = len(x.f_code.co_freevars)
         extras = x.f_code.co_stacksize + x.f_code.co_nlocals +\
                   ncells + nfrees - 1
-        check(x, vsize('13P3i' + CO_MAXBLOCKS*'3i' + 'P' + extras*'P'))
+        check(x, vsize('12P3i' + CO_MAXBLOCKS*'3i' + 'P' + extras*'P'))
         # function
         def func(): pass
         check(func, size('12P'))
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -15,9 +15,6 @@ Core and Builtins
 - Issue #17927: Frame objects kept arguments alive if they had been
   copied into a cell, even if the cell was cleared.
 
-- Issue #17807: Generators can now be finalized even when they are part of
-  a reference cycle.
-
 - Issue #1545463: At shutdown, defer finalization of codec modules so
   that stderr remains usable.
 
diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
@@ -524,7 +524,10 @@ untrack_dicts(PyGC_Head *head)
 static int
 has_finalizer(PyObject *op)
 {
-    return op->ob_type->tp_del != NULL;
+    if (PyGen_CheckExact(op))
+        return PyGen_NeedsFinalizing((PyGenObject *)op);
+    else
+        return op->ob_type->tp_del != NULL;
 }
 
 /* Move the objects in unreachable with __del__ methods into `finalizers`.
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
diff --git a/Objects/genobject.c b/Objects/genobject.c

Original file line number	Diff line number	Diff line change
`@@ -524,7 +524,10 @@ untrack_dicts(PyGC_Head *head)`
`524`	`524`	`static int`
`525`	`525`	`has_finalizer(PyObject *op)`
`526`	`526`	`{`
`527`		`- return op->ob_type->tp_del != NULL;`
	`527`	`+ if (PyGen_CheckExact(op))`
	`528`	`+ return PyGen_NeedsFinalizing((PyGenObject *)op);`
	`529`	`+ else`
	`530`	`+ return op->ob_type->tp_del != NULL;`
`528`	`531`	`}`
`529`	`532`
`530`	`533`	/* Move the objects in unreachable with __del__ methods into `finalizers`.