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bpo-36922: implement PEP-590 Py_TPFLAGS_METHOD_DESCRIPTOR (GH-13338) 

Co-authored-by: Mark Shannon <mark@hotpy.org>
This commit is contained in:
Jeroen Demeyer 2019-05-28 14:42:53 +02:00 committed by Petr Viktorin
parent 0811f2d81a
commit eb65e2443a
10 changed files with 132 additions and 7 deletions
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26
Doc/c-api/typeobj.rst
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@ -1045,6 +1045,32 @@ and :c:type:`PyType_Type` effectively act as defaults.)
???
.. data:: Py_TPFLAGS_METHOD_DESCRIPTOR
This bit indicates that objects behave like unbound methods.
If this flag is set for ``type(meth)``, then:
- ``meth.__get__(obj, cls)(*args, **kwds)`` (with ``obj`` not None)
must be equivalent to ``meth(obj, *args, **kwds)``.
- ``meth.__get__(None, cls)(*args, **kwds)``
must be equivalent to ``meth(*args, **kwds)``.
This flag enables an optimization for typical method calls like
``obj.meth()``: it avoids creating a temporary "bound method" object for
``obj.meth``.
.. versionadded:: 3.8
**Inheritance:**
This flag is never inherited by heap types.
For extension types, it is inherited whenever
:c:member:`~PyTypeObject.tp_descr_get` is inherited.
.. XXX Document more flags here?

3
Include/object.h
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@ -307,6 +307,9 @@ given type object has a specified feature.
#define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION 0
#endif
/* Objects behave like an unbound method */
#define Py_TPFLAGS_METHOD_DESCRIPTOR (1UL << 17)
/* Objects support type attribute cache */
#define Py_TPFLAGS_HAVE_VERSION_TAG (1UL << 18)
#define Py_TPFLAGS_VALID_VERSION_TAG (1UL << 19)

24
Lib/test/test_capi.py
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@ -27,6 +27,8 @@ _testcapi = support.import_module('_testcapi')
# Were we compiled --with-pydebug or with #define Py_DEBUG?
Py_DEBUG = hasattr(sys, 'gettotalrefcount')
Py_TPFLAGS_METHOD_DESCRIPTOR = 1 << 17
def testfunction(self):
"""some doc"""
@ -456,6 +458,28 @@ class TestPendingCalls(unittest.TestCase):
self.pendingcalls_wait(l, n)
class TestPEP590(unittest.TestCase):
def test_method_descriptor_flag(self):
import functools
cached = functools.lru_cache(1)(testfunction)
self.assertFalse(type(repr).__flags__ & Py_TPFLAGS_METHOD_DESCRIPTOR)
self.assertTrue(type(list.append).__flags__ & Py_TPFLAGS_METHOD_DESCRIPTOR)
self.assertTrue(type(list.__add__).__flags__ & Py_TPFLAGS_METHOD_DESCRIPTOR)
self.assertTrue(type(testfunction).__flags__ & Py_TPFLAGS_METHOD_DESCRIPTOR)
self.assertTrue(type(cached).__flags__ & Py_TPFLAGS_METHOD_DESCRIPTOR)
self.assertTrue(_testcapi.MethodDescriptorBase.__flags__ & Py_TPFLAGS_METHOD_DESCRIPTOR)
self.assertTrue(_testcapi.MethodDescriptorDerived.__flags__ & Py_TPFLAGS_METHOD_DESCRIPTOR)
self.assertFalse(_testcapi.MethodDescriptorNopGet.__flags__ & Py_TPFLAGS_METHOD_DESCRIPTOR)
# Heap type should not inherit Py_TPFLAGS_METHOD_DESCRIPTOR
class MethodDescriptorHeap(_testcapi.MethodDescriptorBase):
pass
self.assertFalse(MethodDescriptorHeap.__flags__ & Py_TPFLAGS_METHOD_DESCRIPTOR)
class SubinterpreterTest(unittest.TestCase):
def test_subinterps(self):

3
Misc/NEWS.d/next/C API/2019-05-15-10-46-55.bpo-36922.J3EFK_.rst Normal file
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@ -0,0 +1,3 @@
Add new type flag ``Py_TPFLAGS_METHOD_DESCRIPTOR`` for objects behaving like
unbound methods. These are objects supporting the optimization given by the
``LOAD_METHOD``/``CALL_METHOD`` opcodes. See PEP 590.

3
Modules/_functoolsmodule.c
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@ -1333,7 +1333,8 @@ static PyTypeObject lru_cache_type = {
0, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT|Py_TPFLAGS_BASETYPE|Py_TPFLAGS_HAVE_GC,
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_METHOD_DESCRIPTOR,
/* tp_flags */
lru_cache_doc, /* tp_doc */
(traverseproc)lru_cache_tp_traverse,/* tp_traverse */

57
Modules/_testcapimodule.c
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@ -5787,6 +5787,46 @@ static PyTypeObject Generic_Type = {
};
/* Test PEP 590 */
static PyObject *
func_descr_get(PyObject *func, PyObject *obj, PyObject *type)
{
if (obj == Py_None || obj == NULL) {
Py_INCREF(func);
return func;
}
return PyMethod_New(func, obj);
}
static PyObject *
nop_descr_get(PyObject *func, PyObject *obj, PyObject *type)
{
Py_INCREF(func);
return func;
}
static PyTypeObject MethodDescriptorBase_Type = {
PyVarObject_HEAD_INIT(NULL, 0)
"MethodDescriptorBase",
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_METHOD_DESCRIPTOR,
.tp_descr_get = func_descr_get,
};
static PyTypeObject MethodDescriptorDerived_Type = {
PyVarObject_HEAD_INIT(NULL, 0)
"MethodDescriptorDerived",
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
};
static PyTypeObject MethodDescriptorNopGet_Type = {
PyVarObject_HEAD_INIT(NULL, 0)
"MethodDescriptorNopGet",
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
.tp_descr_get = nop_descr_get,
};
static struct PyModuleDef _testcapimodule = {
PyModuleDef_HEAD_INIT,
"_testcapi",
@ -5834,6 +5874,23 @@ PyInit__testcapi(void)
Py_INCREF(&MyList_Type);
PyModule_AddObject(m, "MyList", (PyObject *)&MyList_Type);
if (PyType_Ready(&MethodDescriptorBase_Type) < 0)
return NULL;
Py_INCREF(&MethodDescriptorBase_Type);
PyModule_AddObject(m, "MethodDescriptorBase", (PyObject *)&MethodDescriptorBase_Type);
MethodDescriptorDerived_Type.tp_base = &MethodDescriptorBase_Type;
if (PyType_Ready(&MethodDescriptorDerived_Type) < 0)
return NULL;
Py_INCREF(&MethodDescriptorDerived_Type);
PyModule_AddObject(m, "MethodDescriptorDerived", (PyObject *)&MethodDescriptorDerived_Type);
MethodDescriptorNopGet_Type.tp_base = &MethodDescriptorBase_Type;
if (PyType_Ready(&MethodDescriptorNopGet_Type) < 0)
return NULL;
Py_INCREF(&MethodDescriptorNopGet_Type);
PyModule_AddObject(m, "MethodDescriptorNopGet", (PyObject *)&MethodDescriptorNopGet_Type);
if (PyType_Ready(&GenericAlias_Type) < 0)
return NULL;
Py_INCREF(&GenericAlias_Type);

6
Objects/descrobject.c
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@ -556,7 +556,8 @@ PyTypeObject PyMethodDescr_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_METHOD_DESCRIPTOR, /* tp_flags */
0, /* tp_doc */
descr_traverse, /* tp_traverse */
0, /* tp_clear */
@ -705,7 +706,8 @@ PyTypeObject PyWrapperDescr_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_METHOD_DESCRIPTOR, /* tp_flags */
0, /* tp_doc */
descr_traverse, /* tp_traverse */
0, /* tp_clear */

3
Objects/funcobject.c
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@ -663,7 +663,8 @@ PyTypeObject PyFunction_Type = {
0, /* 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_METHOD_DESCRIPTOR, /* tp_flags */
func_new__doc__, /* tp_doc */
(traverseproc)func_traverse, /* tp_traverse */
(inquiry)func_clear, /* tp_clear */

3
Objects/object.c
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@ -1155,8 +1155,7 @@ _PyObject_GetMethod(PyObject *obj, PyObject *name, PyObject **method)
descr = _PyType_Lookup(tp, name);
if (descr != NULL) {
Py_INCREF(descr);
if (PyFunction_Check(descr) ||
(Py_TYPE(descr) == &PyMethodDescr_Type)) {
if (PyType_HasFeature(Py_TYPE(descr), Py_TPFLAGS_METHOD_DESCRIPTOR)) {
meth_found = 1;
} else {
f = descr->ob_type->tp_descr_get;

11
Objects/typeobject.c
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@ -4950,7 +4950,7 @@ static void
inherit_special(PyTypeObject *type, PyTypeObject *base)
{
/* Copying basicsize is connected to the GC flags */
/* Copying tp_traverse and tp_clear is connected to the GC flags */
if (!(type->tp_flags & Py_TPFLAGS_HAVE_GC) &&
(base->tp_flags & Py_TPFLAGS_HAVE_GC) &&
(!type->tp_traverse && !type->tp_clear)) {
@ -5165,6 +5165,15 @@ inherit_slots(PyTypeObject *type, PyTypeObject *base)
}
{
COPYSLOT(tp_descr_get);
/* Inherit Py_TPFLAGS_METHOD_DESCRIPTOR if tp_descr_get was inherited,
* but only for extension types */
if (base->tp_descr_get &&
type->tp_descr_get == base->tp_descr_get &&
!(type->tp_flags & Py_TPFLAGS_HEAPTYPE) &&
(base->tp_flags & Py_TPFLAGS_METHOD_DESCRIPTOR))
{
type->tp_flags |= Py_TPFLAGS_METHOD_DESCRIPTOR;
}
COPYSLOT(tp_descr_set);
COPYSLOT(tp_dictoffset);
COPYSLOT(tp_init);