Backout c89febab4648 following private feedback by Guido.
(Issue #17807: Generators can now be finalized even when they are part of a reference cycle)
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index df7a1de0..6fff370 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -31,195 +31,6 @@
return f->f_locals;
}
-/*
- * Generator support.
- */
-
-PyObject *
-_PyFrame_YieldingFrom(PyFrameObject *f)
-{
- PyObject *yf = NULL;
-
- if (f && f->f_stacktop) {
- PyObject *bytecode = f->f_code->co_code;
- unsigned char *code = (unsigned char *)PyBytes_AS_STRING(bytecode);
-
- if (code[f->f_lasti + 1] != YIELD_FROM)
- return NULL;
- yf = f->f_stacktop[-1];
- Py_INCREF(yf);
- }
- return yf;
-}
-
-PyObject *
-_PyFrame_GeneratorSend(PyFrameObject *f, PyObject *arg, int exc)
-{
- PyThreadState *tstate = PyThreadState_GET();
- PyObject *result;
- PyGenObject *gen = (PyGenObject *) f->f_gen;
-
- assert(gen == NULL || PyGen_CheckExact(gen));
- if (gen && gen->gi_running) {
- PyErr_SetString(PyExc_ValueError,
- "generator already executing");
- return NULL;
- }
- if (f->f_stacktop == NULL) {
- /* Only set exception if send() called, not throw() or next() */
- if (arg && !exc)
- PyErr_SetNone(PyExc_StopIteration);
- return NULL;
- }
-
- if (f->f_lasti == -1) {
- if (arg && arg != Py_None) {
- PyErr_SetString(PyExc_TypeError,
- "can't send non-None value to a "
- "just-started generator");
- return NULL;
- }
- } else {
- /* Push arg onto the frame's value stack */
- result = arg ? arg : Py_None;
- Py_INCREF(result);
- *(f->f_stacktop++) = result;
- }
-
- /* Generators always return to their most recent caller, not
- * necessarily their creator. */
- Py_XINCREF(tstate->frame);
- assert(f->f_back == NULL);
- f->f_back = tstate->frame;
-
- if (gen) {
- Py_INCREF(gen);
- gen->gi_running = 1;
- }
- result = PyEval_EvalFrameEx(f, exc);
- if (gen) {
- gen->gi_running = 0;
- /* In case running the frame has lost all external references
- * to gen, we must be careful not to hold on an invalid object. */
- if (Py_REFCNT(gen) == 1)
- Py_CLEAR(gen);
- else
- Py_DECREF(gen);
- }
-
- /* Don't keep the reference to f_back any longer than necessary. It
- * may keep a chain of frames alive or it could create a reference
- * cycle. */
- assert(f->f_back == tstate->frame);
- Py_CLEAR(f->f_back);
-
- /* If the generator just returned (as opposed to yielding), signal
- * that the generator is exhausted. */
- if (result && f->f_stacktop == NULL) {
- if (result == Py_None) {
- /* Delay exception instantiation if we can */
- PyErr_SetNone(PyExc_StopIteration);
- } else {
- PyObject *e = PyObject_CallFunctionObjArgs(
- PyExc_StopIteration, result, NULL);
- if (e != NULL) {
- PyErr_SetObject(PyExc_StopIteration, e);
- Py_DECREF(e);
- }
- }
- Py_CLEAR(result);
- }
-
- if (f->f_stacktop == NULL) {
- /* generator can't be rerun, so release the frame */
- /* first clean reference cycle through stored exception traceback */
- PyObject *t, *v, *tb;
- t = f->f_exc_type;
- v = f->f_exc_value;
- tb = f->f_exc_traceback;
- f->f_exc_type = NULL;
- f->f_exc_value = NULL;
- f->f_exc_traceback = NULL;
- Py_XDECREF(t);
- Py_XDECREF(v);
- Py_XDECREF(tb);
- if (gen) {
- f->f_gen = NULL;
- Py_CLEAR(gen->gi_frame);
- }
- }
-
- return result;
-}
-
-int
-_PyFrame_CloseIterator(PyObject *yf)
-{
- PyObject *retval = NULL;
- _Py_IDENTIFIER(close);
-
- if (PyGen_CheckExact(yf)) {
- PyFrameObject *f = ((PyGenObject *) yf)->gi_frame;
- assert(f != NULL);
- retval = _PyFrame_Finalize(f);
- if (retval == NULL)
- return -1;
- } else {
- PyObject *meth = _PyObject_GetAttrId(yf, &PyId_close);
- if (meth == NULL) {
- if (!PyErr_ExceptionMatches(PyExc_AttributeError))
- PyErr_WriteUnraisable(yf);
- PyErr_Clear();
- } else {
- retval = PyObject_CallFunction(meth, "");
- Py_DECREF(meth);
- if (retval == NULL)
- return -1;
- }
- }
- Py_XDECREF(retval);
- return 0;
-}
-
-PyObject *
-_PyFrame_Finalize(PyFrameObject *f)
-{
- int err = 0;
- PyObject *retval;
- PyGenObject *gen = (PyGenObject *) f->f_gen;
- PyObject *yf = _PyFrame_YieldingFrom(f);
-
- assert(gen == NULL || PyGen_CheckExact(gen));
- if (yf) {
- if (gen)
- gen->gi_running = 1;
- err = _PyFrame_CloseIterator(yf);
- if (gen)
- gen->gi_running = 0;
- Py_DECREF(yf);
- }
- if (err == 0)
- PyErr_SetNone(PyExc_GeneratorExit);
- retval = _PyFrame_GeneratorSend(f, Py_None, 1);
- if (retval) {
- Py_DECREF(retval);
- PyErr_SetString(PyExc_RuntimeError,
- "generator ignored GeneratorExit");
- return NULL;
- }
- if (PyErr_ExceptionMatches(PyExc_StopIteration)
- || PyErr_ExceptionMatches(PyExc_GeneratorExit)) {
- PyErr_Clear(); /* ignore these errors */
- Py_INCREF(Py_None);
- return Py_None;
- }
- return NULL;
-}
-
-/*
- * Line number support.
- */
-
int
PyFrame_GetLineNumber(PyFrameObject *f)
{
@@ -609,43 +420,32 @@
#define PyFrame_MAXFREELIST 200
static void
-frame_clear(PyFrameObject *f);
-
-static void
frame_dealloc(PyFrameObject *f)
{
+ PyObject **p, **valuestack;
PyCodeObject *co;
- Py_REFCNT(f)++;
- frame_clear(f);
- Py_REFCNT(f)--;
- if (Py_REFCNT(f) > 0) {
- /* Frame resurrected! */
- Py_ssize_t refcnt = Py_REFCNT(f);
- _Py_NewReference((PyObject *) f);
- Py_REFCNT(f) = refcnt;
- /* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
- * we need to undo that. */
- _Py_DEC_REFTOTAL;
- /* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
- * chain, so no more to do there.
- * If COUNT_ALLOCS, the original decref bumped tp_frees, and
- * _Py_NewReference bumped tp_allocs: both of those need to be
- * undone.
- */
-#ifdef COUNT_ALLOCS
- --(Py_TYPE(self)->tp_frees);
- --(Py_TYPE(self)->tp_allocs);
-#endif
- }
-
PyObject_GC_UnTrack(f);
Py_TRASHCAN_SAFE_BEGIN(f)
+ /* Kill all local variables */
+ valuestack = f->f_valuestack;
+ for (p = f->f_localsplus; p < valuestack; p++)
+ Py_CLEAR(*p);
+
+ /* Free stack */
+ if (f->f_stacktop != NULL) {
+ for (p = valuestack; p < f->f_stacktop; p++)
+ Py_XDECREF(*p);
+ }
Py_XDECREF(f->f_back);
Py_DECREF(f->f_builtins);
Py_DECREF(f->f_globals);
Py_CLEAR(f->f_locals);
+ Py_CLEAR(f->f_trace);
+ Py_CLEAR(f->f_exc_type);
+ Py_CLEAR(f->f_exc_value);
+ Py_CLEAR(f->f_exc_traceback);
co = f->f_code;
if (co->co_zombieframe == NULL)
@@ -697,25 +497,12 @@
{
PyObject **fastlocals, **p, **oldtop;
Py_ssize_t i, slots;
- PyObject *retval;
- if (f->f_back == NULL) {
- PyObject *t, *v, *tb;
- PyErr_Fetch(&t, &v, &tb);
- /* Note that this can finalize a suspended generator frame even
- * if the generator object was disposed of (i.e. if f_gen is NULL).
- */
- retval = _PyFrame_Finalize(f);
- if (retval == NULL) {
- if (PyErr_Occurred())
- PyErr_WriteUnraisable((PyObject *) f);
- }
- else
- Py_DECREF(retval);
- PyErr_Restore(t, v, tb);
- }
-
- /* Make sure the frame is now clearly marked as being defunct */
+ /* Before anything else, make sure that this frame is clearly marked
+ * as being defunct! Else, e.g., a generator reachable from this
+ * frame may also point to this frame, believe itself to still be
+ * active, and try cleaning up this frame again.
+ */
oldtop = f->f_stacktop;
f->f_stacktop = NULL;
@@ -926,7 +713,6 @@
f->f_lasti = -1;
f->f_lineno = code->co_firstlineno;
f->f_iblock = 0;
- f->f_gen = NULL;
_PyObject_GC_TRACK(f);
return f;