[Python-checkins] gh-103743: Add PyUnstable_Object_GC_NewWithExtraData (GH-103744)
encukou
webhook-mailer at python.org
Tue May 2 07:38:53 EDT 2023
https://github.com/python/cpython/commit/87223f32aba872cfebde6fbe38673799eb79f248
commit: 87223f32aba872cfebde6fbe38673799eb79f248
branch: main
author: Jurica Bradarić <jbradaric at users.noreply.github.com>
committer: encukou <encukou at gmail.com>
date: 2023-05-02T13:38:46+02:00
summary:
gh-103743: Add PyUnstable_Object_GC_NewWithExtraData (GH-103744)
Co-authored-by: Petr Viktorin <encukou at gmail.com>
Co-authored-by: Erlend E. Aasland <erlend.aasland at protonmail.com>
files:
A Misc/NEWS.d/next/C API/2023-04-24-10-31-59.gh-issue-103743.2xYA1K.rst
M Doc/c-api/gcsupport.rst
M Include/cpython/objimpl.h
M Lib/test/test_capi/test_misc.py
M Modules/_testcapimodule.c
M Modules/gcmodule.c
diff --git a/Doc/c-api/gcsupport.rst b/Doc/c-api/gcsupport.rst
index cb5d64a50487..c3260a21bc7f 100644
--- a/Doc/c-api/gcsupport.rst
+++ b/Doc/c-api/gcsupport.rst
@@ -59,12 +59,31 @@ rules:
Analogous to :c:func:`PyObject_New` but for container objects with the
:const:`Py_TPFLAGS_HAVE_GC` flag set.
-
.. c:function:: TYPE* PyObject_GC_NewVar(TYPE, PyTypeObject *type, Py_ssize_t size)
Analogous to :c:func:`PyObject_NewVar` but for container objects with the
:const:`Py_TPFLAGS_HAVE_GC` flag set.
+.. c:function:: PyObject* PyUnstable_Object_GC_NewWithExtraData(PyTypeObject *type, size_t extra_size)
+
+ Analogous to :c:func:`PyObject_GC_New` but allocates *extra_size*
+ bytes at the end of the object (at offset
+ :c:member:`~PyTypeObject.tp_basicsize`).
+ The allocated memory is initialized to zeros,
+ except for the :c:type:`Python object header <PyObject>`.
+
+ The extra data will be deallocated with the object, but otherwise it is
+ not managed by Python.
+
+ .. warning::
+ The function is marked as unstable because the final mechanism
+ for reserving extra data after an instance is not yet decided.
+ For allocating a variable number of fields, prefer using
+ :c:type:`PyVarObject` and :c:member:`~PyTypeObject.tp_itemsize`
+ instead.
+
+ .. versionadded:: 3.12
+
.. c:function:: TYPE* PyObject_GC_Resize(TYPE, PyVarObject *op, Py_ssize_t newsize)
diff --git a/Include/cpython/objimpl.h b/Include/cpython/objimpl.h
index 0b038d31080b..5a8cdd57c784 100644
--- a/Include/cpython/objimpl.h
+++ b/Include/cpython/objimpl.h
@@ -90,3 +90,6 @@ PyAPI_FUNC(int) PyObject_IS_GC(PyObject *obj);
PyAPI_FUNC(int) PyType_SUPPORTS_WEAKREFS(PyTypeObject *type);
PyAPI_FUNC(PyObject **) PyObject_GET_WEAKREFS_LISTPTR(PyObject *op);
+
+PyAPI_FUNC(PyObject *) PyUnstable_Object_GC_NewWithExtraData(PyTypeObject *,
+ size_t);
diff --git a/Lib/test/test_capi/test_misc.py b/Lib/test/test_capi/test_misc.py
index 9470cf12a7d1..9d5d1ca6e7dc 100644
--- a/Lib/test/test_capi/test_misc.py
+++ b/Lib/test/test_capi/test_misc.py
@@ -1043,6 +1043,20 @@ class dictsub(dict): ... # dict subclasses must work
self.assertEqual(_testcapi.function_get_kw_defaults(some), None)
self.assertEqual(some.__kwdefaults__, None)
+ def test_unstable_gc_new_with_extra_data(self):
+ class Data(_testcapi.ObjExtraData):
+ __slots__ = ('x', 'y')
+
+ d = Data()
+ d.x = 10
+ d.y = 20
+ d.extra = 30
+ self.assertEqual(d.x, 10)
+ self.assertEqual(d.y, 20)
+ self.assertEqual(d.extra, 30)
+ del d.extra
+ self.assertIsNone(d.extra)
+
class TestPendingCalls(unittest.TestCase):
diff --git a/Misc/NEWS.d/next/C API/2023-04-24-10-31-59.gh-issue-103743.2xYA1K.rst b/Misc/NEWS.d/next/C API/2023-04-24-10-31-59.gh-issue-103743.2xYA1K.rst
new file mode 100644
index 000000000000..d074350ed3eb
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2023-04-24-10-31-59.gh-issue-103743.2xYA1K.rst
@@ -0,0 +1,2 @@
+Add :c:func:`PyUnstable_Object_GC_NewWithExtraData` function that can be used to
+allocate additional memory after an object for data not managed by Python.
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index c1892f6fa0a4..a5d23b1b3d50 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -3363,7 +3363,7 @@ test_gc_visit_objects_basic(PyObject *Py_UNUSED(self),
}
state.target = obj;
state.found = 0;
-
+
PyUnstable_GC_VisitObjects(gc_visit_callback_basic, &state);
Py_DECREF(obj);
if (!state.found) {
@@ -3400,6 +3400,98 @@ test_gc_visit_objects_exit_early(PyObject *Py_UNUSED(self),
Py_RETURN_NONE;
}
+typedef struct {
+ PyObject_HEAD
+} ObjExtraData;
+
+static PyObject *
+obj_extra_data_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+ size_t extra_size = sizeof(PyObject *);
+ PyObject *obj = PyUnstable_Object_GC_NewWithExtraData(type, extra_size);
+ if (obj == NULL) {
+ return PyErr_NoMemory();
+ }
+ PyObject_GC_Track(obj);
+ return obj;
+}
+
+static PyObject **
+obj_extra_data_get_extra_storage(PyObject *self)
+{
+ return (PyObject **)((char *)self + Py_TYPE(self)->tp_basicsize);
+}
+
+static PyObject *
+obj_extra_data_get(PyObject *self, void *Py_UNUSED(ignored))
+{
+ PyObject **extra_storage = obj_extra_data_get_extra_storage(self);
+ PyObject *value = *extra_storage;
+ if (!value) {
+ Py_RETURN_NONE;
+ }
+ return Py_NewRef(value);
+}
+
+static int
+obj_extra_data_set(PyObject *self, PyObject *newval, void *Py_UNUSED(ignored))
+{
+ PyObject **extra_storage = obj_extra_data_get_extra_storage(self);
+ Py_CLEAR(*extra_storage);
+ if (newval) {
+ *extra_storage = Py_NewRef(newval);
+ }
+ return 0;
+}
+
+static PyGetSetDef obj_extra_data_getset[] = {
+ {"extra", (getter)obj_extra_data_get, (setter)obj_extra_data_set, NULL},
+ {NULL}
+};
+
+static int
+obj_extra_data_traverse(PyObject *self, visitproc visit, void *arg)
+{
+ PyObject **extra_storage = obj_extra_data_get_extra_storage(self);
+ PyObject *value = *extra_storage;
+ Py_VISIT(value);
+ return 0;
+}
+
+static int
+obj_extra_data_clear(PyObject *self)
+{
+ PyObject **extra_storage = obj_extra_data_get_extra_storage(self);
+ Py_CLEAR(*extra_storage);
+ return 0;
+}
+
+static void
+obj_extra_data_dealloc(PyObject *self)
+{
+ PyTypeObject *tp = Py_TYPE(self);
+ PyObject_GC_UnTrack(self);
+ obj_extra_data_clear(self);
+ tp->tp_free(self);
+ Py_DECREF(tp);
+}
+
+static PyType_Slot ObjExtraData_Slots[] = {
+ {Py_tp_getset, obj_extra_data_getset},
+ {Py_tp_dealloc, obj_extra_data_dealloc},
+ {Py_tp_traverse, obj_extra_data_traverse},
+ {Py_tp_clear, obj_extra_data_clear},
+ {Py_tp_new, obj_extra_data_new},
+ {Py_tp_free, PyObject_GC_Del},
+ {0, NULL},
+};
+
+static PyType_Spec ObjExtraData_TypeSpec = {
+ .name = "_testcapi.ObjExtraData",
+ .basicsize = sizeof(ObjExtraData),
+ .flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
+ .slots = ObjExtraData_Slots,
+};
struct atexit_data {
int called;
@@ -4124,6 +4216,17 @@ PyInit__testcapi(void)
Py_INCREF(&MethStatic_Type);
PyModule_AddObject(m, "MethStatic", (PyObject *)&MethStatic_Type);
+ PyObject *ObjExtraData_Type = PyType_FromModuleAndSpec(
+ m, &ObjExtraData_TypeSpec, NULL);
+ if (ObjExtraData_Type == 0) {
+ return NULL;
+ }
+ int ret = PyModule_AddType(m, (PyTypeObject*)ObjExtraData_Type);
+ Py_DECREF(&ObjExtraData_Type);
+ if (ret < 0) {
+ return NULL;
+ }
+
PyModule_AddObject(m, "CHAR_MAX", PyLong_FromLong(CHAR_MAX));
PyModule_AddObject(m, "CHAR_MIN", PyLong_FromLong(CHAR_MIN));
PyModule_AddObject(m, "UCHAR_MAX", PyLong_FromLong(UCHAR_MAX));
diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
index 3fd5f4cd70e8..8a4d1a439828 100644
--- a/Modules/gcmodule.c
+++ b/Modules/gcmodule.c
@@ -2367,6 +2367,19 @@ _PyObject_GC_NewVar(PyTypeObject *tp, Py_ssize_t nitems)
return op;
}
+PyObject *
+PyUnstable_Object_GC_NewWithExtraData(PyTypeObject *tp, size_t extra_size)
+{
+ size_t presize = _PyType_PreHeaderSize(tp);
+ PyObject *op = gc_alloc(_PyObject_SIZE(tp) + extra_size, presize);
+ if (op == NULL) {
+ return NULL;
+ }
+ memset(op, 0, _PyObject_SIZE(tp) + extra_size);
+ _PyObject_Init(op, tp);
+ return op;
+}
+
PyVarObject *
_PyObject_GC_Resize(PyVarObject *op, Py_ssize_t nitems)
{
More information about the Python-checkins
mailing list