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A modest speedup of object deallocation. call_finalizer() did rather 

a lot of work: it had to save and restore the current exception around
a call to lookup_maybe(), because that could fail in rare cases, and
most objects don't have a __del__ method, so the whole exercise was
usually a waste of time.  Changed this to cache the __del__ method in
the type object just like all other special methods, in a new slot
tp_del.  So now subtype_dealloc() can test whether tp_del is NULL and
skip the whole exercise if it is.  The new slot doesn't need a new
flag bit: subtype_dealloc() is only called if the type was dynamically
allocated by type_new(), so it's guaranteed to have all current slots.
Types defined in C cannot fill in tp_del with a function of their own,
so there's no corresponding "wrapper".  (That functionality is already
available through tp_dealloc.)
This commit is contained in:
Guido van Rossum 2002-08-08 20:55:20 +00:00
parent 12e3c710db
commit febd61dc02
2 changed files with 71 additions and 66 deletions
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1
Include/object.h
View File

@ -315,6 +315,7 @@ typedef struct _typeobject {
PyObject *tp_cache;
PyObject *tp_subclasses;
PyObject *tp_weaklist;
destructor tp_del;
#ifdef COUNT_ALLOCS
/* these must be last and never explicitly initialized */

136
Objects/typeobject.c
View File

@ -356,68 +356,6 @@ subtype_clear(PyObject *self)
return 0;
}
static PyObject *lookup_maybe(PyObject *, char *, PyObject **);
static int
call_finalizer(PyObject *self)
{
static PyObject *del_str = NULL;
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);
/* Execute __del__ method, if any. */
del = lookup_maybe(self, "__del__", &del_str);
if (del != NULL) {
res = PyEval_CallObject(del, NULL);
if (res == NULL)
PyErr_WriteUnraisable(del);
else
Py_DECREF(res);
Py_DECREF(del);
}
/* 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 0; /* this is the normal path out */
/* __del__ resurrected it! Make it look like the original Py_DECREF
* never happened.
*/
{
int refcnt = self->ob_refcnt;
_Py_NewReference(self);
self->ob_refcnt = refcnt;
}
assert(!PyType_IS_GC(self->ob_type) ||
_Py_AS_GC(self)->gc.gc_refs != _PyGC_REFS_UNTRACKED);
/* If Py_REF_DEBUG, the original decref dropped _Py_RefTotal, but
* _Py_NewReference bumped it again, so that's a wash.
* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
* chain, so no more to do there either.
* 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
--self->ob_type->tp_frees;
--self->ob_type->tp_allocs;
#endif
return -1; /* __del__ added a reference; don't delete now */
}
static void
subtype_dealloc(PyObject *self)
{
@ -438,8 +376,11 @@ subtype_dealloc(PyObject *self)
clear_slots(), or DECREF the dict, or clear weakrefs. */
/* Maybe call finalizer; exit early if resurrected */
if (call_finalizer(self) < 0)
return;
if (type->tp_del) {
type->tp_del(self);
if (self->ob_refcnt > 0)
return;
}
/* Find the nearest base with a different tp_dealloc */
base = type;
@ -468,8 +409,11 @@ subtype_dealloc(PyObject *self)
_PyObject_GC_TRACK(self); /* We'll untrack for real later */
/* Maybe call finalizer; exit early if resurrected */
if (call_finalizer(self) < 0)
goto endlabel;
if (type->tp_del) {
type->tp_del(self);
if (self->ob_refcnt > 0)
goto endlabel;
}
/* Find the nearest base with a different tp_dealloc
and clear slots while we're at it */
@ -3721,6 +3665,65 @@ slot_tp_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
return x;
}
static void
slot_tp_del(PyObject *self)
{
static PyObject *del_str = NULL;
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);
/* Execute __del__ method, if any. */
del = lookup_maybe(self, "__del__", &del_str);
if (del != NULL) {
res = PyEval_CallObject(del, NULL);
if (res == NULL)
PyErr_WriteUnraisable(del);
else
Py_DECREF(res);
Py_DECREF(del);
}
/* 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.
*/
{
int refcnt = self->ob_refcnt;
_Py_NewReference(self);
self->ob_refcnt = refcnt;
}
assert(!PyType_IS_GC(self->ob_type) ||
_Py_AS_GC(self)->gc.gc_refs != _PyGC_REFS_UNTRACKED);
/* If Py_REF_DEBUG, the original decref dropped _Py_RefTotal, but
* _Py_NewReference bumped it again, so that's a wash.
* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
* chain, so no more to do there either.
* 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
--self->ob_type->tp_frees;
--self->ob_type->tp_allocs;
#endif
}
/* Table mapping __foo__ names to tp_foo offsets and slot_tp_foo wrapper
functions. The offsets here are relative to the 'etype' structure, which
@ -3949,6 +3952,7 @@ static slotdef slotdefs[] = {
"see x.__class__.__doc__ for signature",
PyWrapperFlag_KEYWORDS),
TPSLOT("__new__", tp_new, slot_tp_new, NULL, ""),
TPSLOT("__del__", tp_del, slot_tp_del, NULL, ""),
{NULL}
};