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Issue #18112: PEP 442 implementation (safe object finalization).

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This commit is contained in:
Antoine Pitrou 2013-07-30 19:59:21 +02:00
parent c5d95b17ac
commit 796564c27b
25 changed files with 1254 additions and 321 deletions
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103
Objects/genobject.c
View file

@ -15,6 +15,31 @@ gen_traverse(PyGenObject *gen, visitproc visit, void *arg)
return 0;
}
static void
gen_finalize(PyObject *self)
{
PyGenObject *gen = (PyGenObject *)self;
PyObject *res;
PyObject *error_type, *error_value, *error_traceback;
if (gen->gi_frame == NULL || gen->gi_frame->f_stacktop == NULL)
/* Generator isn't paused, so no need to close */
return;
/* Save the current exception, if any. */
PyErr_Fetch(&error_type, &error_value, &error_traceback);
res = gen_close(gen, NULL);
if (res == NULL)
PyErr_WriteUnraisable(self);
else
Py_DECREF(res);
/* Restore the saved exception. */
PyErr_Restore(error_type, error_value, error_traceback);
}
static void
gen_dealloc(PyGenObject *gen)
{
@ -27,12 +52,8 @@ gen_dealloc(PyGenObject *gen)
_PyObject_GC_TRACK(self);
if (gen->gi_frame != NULL && gen->gi_frame->f_stacktop != NULL) {
/* Generator is paused, so we need to close */
Py_TYPE(gen)->tp_del(self);
if (self->ob_refcnt > 0)
return; /* resurrected. :( */
}
if (PyObject_CallFinalizerFromDealloc(self))
return; /* resurrected. :( */
_PyObject_GC_UNTRACK(self);
Py_CLEAR(gen->gi_frame);
@ -40,7 +61,6 @@ gen_dealloc(PyGenObject *gen)
PyObject_GC_Del(gen);
}
static PyObject *
gen_send_ex(PyGenObject *gen, PyObject *arg, int exc)
{
@ -222,68 +242,6 @@ gen_close(PyGenObject *gen, PyObject *args)
return NULL;
}
static void
gen_del(PyObject *self)
{
PyObject *res;
PyObject *error_type, *error_value, *error_traceback;
PyGenObject *gen = (PyGenObject *)self;
if (gen->gi_frame == NULL || gen->gi_frame->f_stacktop == NULL)
/* Generator isn't paused, so no need to close */
return;
/* Temporarily resurrect the object. */
assert(self->ob_refcnt == 0);
self->ob_refcnt = 1;
/* Save the current exception, if any. */
PyErr_Fetch(&error_type, &error_value, &error_traceback);
res = gen_close(gen, NULL);
if (res == NULL)
PyErr_WriteUnraisable(self);
else
Py_DECREF(res);
/* Restore the saved exception. */
PyErr_Restore(error_type, error_value, error_traceback);
/* Undo the temporary resurrection; can't use DECREF here, it would
* cause a recursive call.
*/
assert(self->ob_refcnt > 0);
if (--self->ob_refcnt == 0)
return; /* this is the normal path out */
/* close() resurrected it! Make it look like the original Py_DECREF
* never happened.
*/
{
Py_ssize_t refcnt = self->ob_refcnt;
_Py_NewReference(self);
self->ob_refcnt = refcnt;
}
assert(PyType_IS_GC(Py_TYPE(self)) &&
_Py_AS_GC(self)->gc.gc_refs != _PyGC_REFS_UNTRACKED);
/* 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
}
PyDoc_STRVAR(throw_doc,
"throw(typ[,val[,tb]]) -> raise exception in generator,\n\
@ -517,7 +475,8 @@ PyTypeObject PyGen_Type = {
PyObject_GenericGetAttr, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
Py_TPFLAGS_HAVE_FINALIZE, /* tp_flags */
0, /* tp_doc */
(traverseproc)gen_traverse, /* tp_traverse */
0, /* tp_clear */
@ -544,7 +503,9 @@ PyTypeObject PyGen_Type = {
0, /* tp_cache */
0, /* tp_subclasses */
0, /* tp_weaklist */
gen_del, /* tp_del */
0, /* tp_del */
0, /* tp_version_tag */
gen_finalize, /* tp_finalize */
};
PyObject *

70
Objects/object.c
View file

@ -255,6 +255,72 @@ _PyObject_NewVar(PyTypeObject *tp, Py_ssize_t nitems)
return PyObject_INIT_VAR(op, tp, nitems);
}
void
PyObject_CallFinalizer(PyObject *self)
{
PyTypeObject *tp = Py_TYPE(self);
/* The former could happen on heaptypes created from the C API, e.g.
PyType_FromSpec(). */
if (!PyType_HasFeature(tp, Py_TPFLAGS_HAVE_FINALIZE) ||
tp->tp_finalize == NULL)
return;
/* tp_finalize should only be called once. */
if (PyType_IS_GC(tp) && _PyGC_FINALIZED(self))
return;
tp->tp_finalize(self);
if (PyType_IS_GC(tp))
_PyGC_SET_FINALIZED(self, 1);
}
int
PyObject_CallFinalizerFromDealloc(PyObject *self)
{
Py_ssize_t refcnt;
/* Temporarily resurrect the object. */
if (self->ob_refcnt != 0) {
Py_FatalError("PyObject_CallFinalizerFromDealloc called on "
"object with a non-zero refcount");
}
self->ob_refcnt = 1;
PyObject_CallFinalizer(self);
/* Undo the temporary resurrection; can't use DECREF here, it would
* cause a recursive call.
*/
assert(self->ob_refcnt > 0);
if (--self->ob_refcnt == 0)
return 0; /* this is the normal path out */
/* tp_finalize resurrected it! Make it look like the original Py_DECREF
* never happened.
*/
refcnt = self->ob_refcnt;
_Py_NewReference(self);
self->ob_refcnt = refcnt;
if (PyType_IS_GC(Py_TYPE(self))) {
assert(_PyGC_REFS(self) != _PyGC_REFS_UNTRACKED);
}
/* 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
return -1;
}
int
PyObject_Print(PyObject *op, FILE *fp, int flags)
{
@ -1981,7 +2047,7 @@ void
_PyTrash_deposit_object(PyObject *op)
{
assert(PyObject_IS_GC(op));
assert(_Py_AS_GC(op)->gc.gc_refs == _PyGC_REFS_UNTRACKED);
assert(_PyGC_REFS(op) == _PyGC_REFS_UNTRACKED);
assert(op->ob_refcnt == 0);
_Py_AS_GC(op)->gc.gc_prev = (PyGC_Head *)_PyTrash_delete_later;
_PyTrash_delete_later = op;
@ -1993,7 +2059,7 @@ _PyTrash_thread_deposit_object(PyObject *op)
{
PyThreadState *tstate = PyThreadState_GET();
assert(PyObject_IS_GC(op));
assert(_Py_AS_GC(op)->gc.gc_refs == _PyGC_REFS_UNTRACKED);
assert(_PyGC_REFS(op) == _PyGC_REFS_UNTRACKED);
assert(op->ob_refcnt == 0);
_Py_AS_GC(op)->gc.gc_prev = (PyGC_Head *) tstate->trash_delete_later;
tstate->trash_delete_later = op;

97
Objects/typeobject.c
View file

@ -921,6 +921,7 @@ subtype_dealloc(PyObject *self)
PyTypeObject *type, *base;
destructor basedealloc;
PyThreadState *tstate = PyThreadState_GET();
int has_finalizer;
/* Extract the type; we expect it to be a heap type */
type = Py_TYPE(self);
@ -936,6 +937,10 @@ subtype_dealloc(PyObject *self)
clear_slots(), or DECREF the dict, or clear weakrefs. */
/* Maybe call finalizer; exit early if resurrected */
if (type->tp_finalize) {
if (PyObject_CallFinalizerFromDealloc(self) < 0)
return;
}
if (type->tp_del) {
type->tp_del(self);
if (self->ob_refcnt > 0)
@ -987,25 +992,36 @@ subtype_dealloc(PyObject *self)
assert(base);
}
/* If we added a weaklist, we clear it. Do this *before* calling
the finalizer (__del__), clearing slots, or clearing the instance
dict. */
has_finalizer = type->tp_finalize || type->tp_del;
/* Maybe call finalizer; exit early if resurrected */
if (has_finalizer)
_PyObject_GC_TRACK(self);
if (type->tp_finalize) {
if (PyObject_CallFinalizerFromDealloc(self) < 0) {
/* Resurrected */
goto endlabel;
}
}
/* If we added a weaklist, we clear it. Do this *before* calling
tp_del, clearing slots, or clearing the instance dict. */
if (type->tp_weaklistoffset && !base->tp_weaklistoffset)
PyObject_ClearWeakRefs(self);
/* Maybe call finalizer; exit early if resurrected */
if (type->tp_del) {
_PyObject_GC_TRACK(self);
type->tp_del(self);
if (self->ob_refcnt > 0)
goto endlabel; /* resurrected */
else
_PyObject_GC_UNTRACK(self);
if (self->ob_refcnt > 0) {
/* Resurrected */
goto endlabel;
}
}
if (has_finalizer) {
_PyObject_GC_UNTRACK(self);
/* New weakrefs could be created during the finalizer call.
If this occurs, clear them out without calling their
finalizers since they might rely on part of the object
being finalized that has already been destroyed. */
If this occurs, clear them out without calling their
finalizers since they might rely on part of the object
being finalized that has already been destroyed. */
if (type->tp_weaklistoffset && !base->tp_weaklistoffset) {
/* Modeled after GET_WEAKREFS_LISTPTR() */
PyWeakReference **list = (PyWeakReference **) \
@ -2231,7 +2247,7 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
/* Initialize tp_flags */
type->tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HEAPTYPE |
Py_TPFLAGS_BASETYPE;
Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_FINALIZE;
if (base->tp_flags & Py_TPFLAGS_HAVE_GC)
type->tp_flags |= Py_TPFLAGS_HAVE_GC;
@ -4111,6 +4127,10 @@ inherit_slots(PyTypeObject *type, PyTypeObject *base)
COPYSLOT(tp_init);
COPYSLOT(tp_alloc);
COPYSLOT(tp_is_gc);
if ((type->tp_flags & Py_TPFLAGS_HAVE_FINALIZE) &&
(base->tp_flags & Py_TPFLAGS_HAVE_FINALIZE)) {
COPYSLOT(tp_finalize);
}
if ((type->tp_flags & Py_TPFLAGS_HAVE_GC) ==
(base->tp_flags & Py_TPFLAGS_HAVE_GC)) {
/* They agree about gc. */
@ -4736,6 +4756,18 @@ wrap_call(PyObject *self, PyObject *args, void *wrapped, PyObject *kwds)
return (*func)(self, args, kwds);
}
static PyObject *
wrap_del(PyObject *self, PyObject *args, void *wrapped)
{
destructor func = (destructor)wrapped;
if (!check_num_args(args, 0))
return NULL;
(*func)(self);
Py_RETURN_NONE;
}
static PyObject *
wrap_richcmpfunc(PyObject *self, PyObject *args, void *wrapped, int op)
{
@ -5617,16 +5649,12 @@ slot_tp_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
}
static void
slot_tp_del(PyObject *self)
slot_tp_finalize(PyObject *self)
{
_Py_IDENTIFIER(__del__);
PyObject *del, *res;
PyObject *error_type, *error_value, *error_traceback;
/* Temporarily resurrect the object. */
assert(self->ob_refcnt == 0);
self->ob_refcnt = 1;
/* Save the current exception, if any. */
PyErr_Fetch(&error_type, &error_value, &error_traceback);
@ -5643,37 +5671,6 @@ slot_tp_del(PyObject *self)
/* Restore the saved exception. */
PyErr_Restore(error_type, error_value, error_traceback);
/* Undo the temporary resurrection; can't use DECREF here, it would
* cause a recursive call.
*/
assert(self->ob_refcnt > 0);
if (--self->ob_refcnt == 0)
return; /* this is the normal path out */
/* __del__ resurrected it! Make it look like the original Py_DECREF
* never happened.
*/
{
Py_ssize_t refcnt = self->ob_refcnt;
_Py_NewReference(self);
self->ob_refcnt = refcnt;
}
assert(!PyType_IS_GC(Py_TYPE(self)) ||
_Py_AS_GC(self)->gc.gc_refs != _PyGC_REFS_UNTRACKED);
/* 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
}
@ -5782,7 +5779,7 @@ static slotdef slotdefs[] = {
"see help(type(x)) for signature",
PyWrapperFlag_KEYWORDS),
TPSLOT("__new__", tp_new, slot_tp_new, NULL, ""),
TPSLOT("__del__", tp_del, slot_tp_del, NULL, ""),
TPSLOT("__del__", tp_finalize, slot_tp_finalize, (wrapperfunc)wrap_del, ""),
BINSLOT("__add__", nb_add, slot_nb_add,
"+"),