bpo-36974: implement PEP 590 (GH-13185)

Co-authored-by: Jeroen Demeyer <J.Demeyer@UGent.be>
Co-authored-by: Mark Shannon <mark@hotpy.org>

Include/classobject.h

@@ -14,6 +14,7 @@ typedef struct {
     PyObject *im_func;   /* The callable object implementing the method */
     PyObject *im_self;   /* The instance it is bound to */
     PyObject *im_weakreflist; /* List of weak references */
+    vectorcallfunc vectorcall;
 } PyMethodObject;
 
 PyAPI_DATA(PyTypeObject) PyMethod_Type;

Include/cpython/abstract.h

@@ -47,7 +47,7 @@ PyAPI_FUNC(int) _PyStack_UnpackDict(
 /* Suggested size (number of positional arguments) for arrays of PyObject*
    allocated on a C stack to avoid allocating memory on the heap memory. Such
    array is used to pass positional arguments to call functions of the
-   _PyObject_FastCall() family.
+   _PyObject_Vectorcall() family.
 
    The size is chosen to not abuse the C stack and so limit the risk of stack
    overflow. The size is also chosen to allow using the small stack for most
@@ -56,50 +56,103 @@ PyAPI_FUNC(int) _PyStack_UnpackDict(
 #define _PY_FASTCALL_SMALL_STACK 5
 
 /* Return 1 if callable supports FASTCALL calling convention for positional
-   arguments: see _PyObject_FastCallDict() and _PyObject_FastCallKeywords() */
+   arguments: see _PyObject_Vectorcall() and _PyObject_FastCallDict() */
 PyAPI_FUNC(int) _PyObject_HasFastCall(PyObject *callable);
 
-/* Call the callable object 'callable' with the "fast call" calling convention:
-   args is a C array for positional arguments (nargs is the number of
-   positional arguments), kwargs is a dictionary for keyword arguments.
+PyAPI_FUNC(PyObject *) _Py_CheckFunctionResult(PyObject *callable,
+                                               PyObject *result,
+                                               const char *where);
 
-   If nargs is equal to zero, args can be NULL. kwargs can be NULL.
-   nargs must be greater or equal to zero.
+/* === Vectorcall protocol (PEP 590) ============================= */
+
+/* Call callable using tp_call. Arguments are like _PyObject_Vectorcall()
+   or _PyObject_FastCallDict() (both forms are supported),
+   except that nargs is plainly the number of arguments without flags. */
+PyAPI_FUNC(PyObject *) _PyObject_MakeTpCall(
+    PyObject *callable,
+    PyObject *const *args, Py_ssize_t nargs,
+    PyObject *keywords);
+
+#define PY_VECTORCALL_ARGUMENTS_OFFSET ((size_t)1 << (8 * sizeof(size_t) - 1))
+
+static inline Py_ssize_t
+PyVectorcall_NARGS(size_t n)
+{
+    return n & ~PY_VECTORCALL_ARGUMENTS_OFFSET;
+}
+
+static inline vectorcallfunc
+_PyVectorcall_Function(PyObject *callable)
+{
+    PyTypeObject *tp = Py_TYPE(callable);
+    if (!PyType_HasFeature(tp, _Py_TPFLAGS_HAVE_VECTORCALL)) {
+        return NULL;
+    }
+    assert(PyCallable_Check(callable));
+    Py_ssize_t offset = tp->tp_vectorcall_offset;
+    assert(offset > 0);
+    vectorcallfunc *ptr = (vectorcallfunc *)(((char *)callable) + offset);
+    return *ptr;
+}
+
+/* Call the callable object 'callable' with the "vectorcall" calling
+   convention.
+
+   args is a C array for positional arguments.
+
+   nargsf is the number of positional arguments plus optionally the flag
+   PY_VECTORCALL_ARGUMENTS_OFFSET which means that the caller is allowed to
+   modify args[-1].
+
+   kwnames is a tuple of keyword names. The values of the keyword arguments
+   are stored in "args" after the positional arguments (note that the number
+   of keyword arguments does not change nargsf). kwnames can also be NULL if
+   there are no keyword arguments.
+
+   keywords must only contains str strings (no subclass), and all keys must
+   be unique.
 
    Return the result on success. Raise an exception and return NULL on
    error. */
+static inline PyObject *
+_PyObject_Vectorcall(PyObject *callable, PyObject *const *args,
+                     size_t nargsf, PyObject *kwnames)
+{
+    assert(kwnames == NULL || PyTuple_Check(kwnames));
+    assert(args != NULL || PyVectorcall_NARGS(nargsf) == 0);
+    vectorcallfunc func = _PyVectorcall_Function(callable);
+    if (func == NULL) {
+        Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
+        return _PyObject_MakeTpCall(callable, args, nargs, kwnames);
+    }
+    PyObject *res = func(callable, args, nargsf, kwnames);
+    return _Py_CheckFunctionResult(callable, res, NULL);
+}
+
+/* Same as _PyObject_Vectorcall except that keyword arguments are passed as
+   dict, which may be NULL if there are no keyword arguments. */
 PyAPI_FUNC(PyObject *) _PyObject_FastCallDict(
     PyObject *callable,
     PyObject *const *args,
-    Py_ssize_t nargs,
+    size_t nargsf,
     PyObject *kwargs);
 
-/* Call the callable object 'callable' with the "fast call" calling convention:
-   args is a C array for positional arguments followed by values of
-   keyword arguments. Keys of keyword arguments are stored as a tuple
-   of strings in kwnames. nargs is the number of positional parameters at
-   the beginning of stack. The size of kwnames gives the number of keyword
-   values in the stack after positional arguments.
+/* Call "callable" (which must support vectorcall) with positional arguments
+   "tuple" and keyword arguments "dict". "dict" may also be NULL */
+PyAPI_FUNC(PyObject *) PyVectorcall_Call(PyObject *callable, PyObject *tuple, PyObject *dict);
 
-   kwnames must only contains str strings, no subclass, and all keys must
-   be unique.
+/* Same as _PyObject_Vectorcall except without keyword arguments */
+static inline PyObject *
+_PyObject_FastCall(PyObject *func, PyObject *const *args, Py_ssize_t nargs)
+{
+    return _PyObject_Vectorcall(func, args, (size_t)nargs, NULL);
+}
 
-   If nargs is equal to zero and there is no keyword argument (kwnames is
-   NULL or its size is zero), args can be NULL.
-
-   Return the result on success. Raise an exception and return NULL on
-   error. */
-PyAPI_FUNC(PyObject *) _PyObject_FastCallKeywords(
-    PyObject *callable,
-    PyObject *const *args,
-    Py_ssize_t nargs,
-    PyObject *kwnames);
-
-#define _PyObject_FastCall(func, args, nargs) \
-    _PyObject_FastCallDict((func), (args), (nargs), NULL)
-
-#define _PyObject_CallNoArg(func) \
-    _PyObject_FastCallDict((func), NULL, 0, NULL)
+/* Call a callable without any arguments */
+static inline PyObject *
+_PyObject_CallNoArg(PyObject *func) {
+    return _PyObject_Vectorcall(func, NULL, 0, NULL);
+}
 
 PyAPI_FUNC(PyObject *) _PyObject_Call_Prepend(
     PyObject *callable,
@@ -113,10 +166,6 @@ PyAPI_FUNC(PyObject *) _PyObject_FastCall_Prepend(
     PyObject *const *args,
     Py_ssize_t nargs);
 
-PyAPI_FUNC(PyObject *) _Py_CheckFunctionResult(PyObject *callable,
-                                               PyObject *result,
-                                               const char *where);
-
 /* Like PyObject_CallMethod(), but expect a _Py_Identifier*
    as the method name. */
 PyAPI_FUNC(PyObject *) _PyObject_CallMethodId(PyObject *obj,

Include/cpython/object.h

@@ -55,6 +55,9 @@ typedef struct bufferinfo {
 typedef int (*getbufferproc)(PyObject *, Py_buffer *, int);
 typedef void (*releasebufferproc)(PyObject *, Py_buffer *);
 
+typedef PyObject *(*vectorcallfunc)(PyObject *callable, PyObject *const *args,
+                                    size_t nargsf, PyObject *kwnames);
+
 /* Maximum number of dimensions */
 #define PyBUF_MAX_NDIM 64
 
@@ -167,12 +170,9 @@ typedef struct {
      releasebufferproc bf_releasebuffer;
 } PyBufferProcs;
 
-/* We can't provide a full compile-time check that limited-API
-   users won't implement tp_print. However, not defining printfunc
-   and making tp_print of a different function pointer type
-   if Py_LIMITED_API is set should at least cause a warning
-   in most cases. */
-typedef int (*printfunc)(PyObject *, FILE *, int);
+/* Allow printfunc in the tp_vectorcall_offset slot for
+ * backwards-compatibility */
+typedef Py_ssize_t printfunc;
 
 typedef struct _typeobject {
     PyObject_VAR_HEAD
@@ -182,7 +182,7 @@ typedef struct _typeobject {
     /* Methods to implement standard operations */
 
     destructor tp_dealloc;
-    printfunc tp_print;
+    Py_ssize_t tp_vectorcall_offset;
     getattrfunc tp_getattr;
     setattrfunc tp_setattr;
     PyAsyncMethods *tp_as_async; /* formerly known as tp_compare (Python 2)
@@ -254,6 +254,7 @@ typedef struct _typeobject {
     unsigned int tp_version_tag;
 
     destructor tp_finalize;
+    vectorcallfunc tp_vectorcall;
 
 #ifdef COUNT_ALLOCS
     /* these must be last and never explicitly initialized */

Include/descrobject.h

@@ -53,6 +53,7 @@ typedef struct {
 typedef struct {
     PyDescr_COMMON;
     PyMethodDef *d_method;
+    vectorcallfunc vectorcall;
 } PyMethodDescrObject;
 
 typedef struct {
@@ -92,7 +93,7 @@ PyAPI_FUNC(PyObject *) PyDescr_NewGetSet(PyTypeObject *,
 #ifndef Py_LIMITED_API
 
 PyAPI_FUNC(PyObject *) _PyMethodDescr_FastCallKeywords(
-        PyObject *descrobj, PyObject *const *stack, Py_ssize_t nargs, PyObject *kwnames);
+        PyObject *descrobj, PyObject *const *args, size_t nargsf, PyObject *kwnames);
 PyAPI_FUNC(PyObject *) PyDescr_NewWrapper(PyTypeObject *,
                                                 struct wrapperbase *, void *);
 #define PyDescr_IsData(d) (Py_TYPE(d)->tp_descr_set != NULL)

Include/funcobject.h

@@ -32,6 +32,7 @@ typedef struct {
     PyObject *func_module;      /* The __module__ attribute, can be anything */
     PyObject *func_annotations; /* Annotations, a dict or NULL */
     PyObject *func_qualname;    /* The qualified name */
+    vectorcallfunc vectorcall;
 
     /* Invariant:
      *     func_closure contains the bindings for func_code->co_freevars, so
@@ -68,7 +69,7 @@ PyAPI_FUNC(PyObject *) _PyFunction_FastCallDict(
 PyAPI_FUNC(PyObject *) _PyFunction_FastCallKeywords(
     PyObject *func,
     PyObject *const *stack,
-    Py_ssize_t nargs,
+    size_t nargsf,
     PyObject *kwnames);
 #endif
 

Include/methodobject.h

@@ -49,7 +49,7 @@ PyAPI_FUNC(PyObject *) _PyCFunction_FastCallDict(PyObject *func,
 
 PyAPI_FUNC(PyObject *) _PyCFunction_FastCallKeywords(PyObject *func,
     PyObject *const *stack,
-    Py_ssize_t nargs,
+    size_t nargsf,
     PyObject *kwnames);
 #endif
 
@@ -105,6 +105,7 @@ typedef struct {
     PyObject    *m_self; /* Passed as 'self' arg to the C func, can be NULL */
     PyObject    *m_module; /* The __module__ attribute, can be anything */
     PyObject    *m_weakreflist; /* List of weak references */
+    vectorcallfunc vectorcall;
 } PyCFunctionObject;
 
 PyAPI_FUNC(PyObject *) _PyMethodDef_RawFastCallDict(

Include/object.h

@@ -291,6 +291,11 @@ given type object has a specified feature.
 /* Set if the type allows subclassing */
 #define Py_TPFLAGS_BASETYPE (1UL << 10)
 
+/* Set if the type implements the vectorcall protocol (PEP 590) */
+#ifndef Py_LIMITED_API
+#define _Py_TPFLAGS_HAVE_VECTORCALL (1UL << 11)
+#endif
+
 /* Set if the type is 'ready' -- fully initialized */
 #define Py_TPFLAGS_READY (1UL << 12)
 

Lib/test/test_call.py

@@ -402,7 +402,7 @@ class FastCallTests(unittest.TestCase):
                     result = _testcapi.pyobject_fastcall(func, None)
                     self.check_result(result, expected)
 
-    def test_fastcall_dict(self):
+    def test_vectorcall_dict(self):
         # Test _PyObject_FastCallDict()
 
         for func, args, expected in self.CALLS_POSARGS:
@@ -429,33 +429,33 @@ class FastCallTests(unittest.TestCase):
                 result = _testcapi.pyobject_fastcalldict(func, args, kwargs)
                 self.check_result(result, expected)
 
-    def test_fastcall_keywords(self):
-        # Test _PyObject_FastCallKeywords()
+    def test_vectorcall(self):
+        # Test _PyObject_Vectorcall()
 
         for func, args, expected in self.CALLS_POSARGS:
             with self.subTest(func=func, args=args):
                 # kwnames=NULL
-                result = _testcapi.pyobject_fastcallkeywords(func, args, None)
+                result = _testcapi.pyobject_vectorcall(func, args, None)
                 self.check_result(result, expected)
 
                 # kwnames=()
-                result = _testcapi.pyobject_fastcallkeywords(func, args, ())
+                result = _testcapi.pyobject_vectorcall(func, args, ())
                 self.check_result(result, expected)
 
                 if not args:
                     # kwnames=NULL
-                    result = _testcapi.pyobject_fastcallkeywords(func, None, None)
+                    result = _testcapi.pyobject_vectorcall(func, None, None)
                     self.check_result(result, expected)
 
                     # kwnames=()
-                    result = _testcapi.pyobject_fastcallkeywords(func, None, ())
+                    result = _testcapi.pyobject_vectorcall(func, None, ())
                     self.check_result(result, expected)
 
         for func, args, kwargs, expected in self.CALLS_KWARGS:
             with self.subTest(func=func, args=args, kwargs=kwargs):
                 kwnames = tuple(kwargs.keys())
                 args = args + tuple(kwargs.values())
-                result = _testcapi.pyobject_fastcallkeywords(func, args, kwnames)
+                result = _testcapi.pyobject_vectorcall(func, args, kwnames)
                 self.check_result(result, expected)
 
     def test_fastcall_clearing_dict(self):

Lib/test/test_capi.py

@@ -34,6 +34,11 @@ def testfunction(self):
     """some doc"""
     return self
 
+def testfunction_kw(self, *, kw):
+    """some doc"""
+    return self
+
+
 class InstanceMethod:
     id = _testcapi.instancemethod(id)
     testfunction = _testcapi.instancemethod(testfunction)
@@ -479,6 +484,48 @@ class TestPEP590(unittest.TestCase):
             pass
         self.assertFalse(MethodDescriptorHeap.__flags__ & Py_TPFLAGS_METHOD_DESCRIPTOR)
 
+    def test_vectorcall(self):
+        # Test a bunch of different ways to call objects:
+        # 1. normal call
+        # 2. vectorcall using _PyObject_Vectorcall()
+        # 3. vectorcall using PyVectorcall_Call()
+        # 4. call as bound method
+        # 5. call using functools.partial
+
+        # A list of (function, args, kwargs, result) calls to test
+        calls = [(len, (range(42),), {}, 42),
+                 (list.append, ([], 0), {}, None),
+                 ([].append, (0,), {}, None),
+                 (sum, ([36],), {"start":6}, 42),
+                 (testfunction, (42,), {}, 42),
+                 (testfunction_kw, (42,), {"kw":None}, 42)]
+
+        from _testcapi import pyobject_vectorcall, pyvectorcall_call
+        from types import MethodType
+        from functools import partial
+
+        def vectorcall(func, args, kwargs):
+            args = *args, *kwargs.values()
+            kwnames = tuple(kwargs)
+            return pyobject_vectorcall(func, args, kwnames)
+
+        for (func, args, kwargs, expected) in calls:
+            with self.subTest(str(func)):
+                args1 = args[1:]
+                meth = MethodType(func, args[0])
+                wrapped = partial(func)
+                if not kwargs:
+                    self.assertEqual(expected, func(*args))
+                    self.assertEqual(expected, pyobject_vectorcall(func, args, None))
+                    self.assertEqual(expected, pyvectorcall_call(func, args))
+                    self.assertEqual(expected, meth(*args1))
+                    self.assertEqual(expected, wrapped(*args))
+                self.assertEqual(expected, func(*args, **kwargs))
+                self.assertEqual(expected, vectorcall(func, args, kwargs))
+                self.assertEqual(expected, pyvectorcall_call(func, args, kwargs))
+                self.assertEqual(expected, meth(*args1, **kwargs))
+                self.assertEqual(expected, wrapped(*args, **kwargs))
+
 
 class SubinterpreterTest(unittest.TestCase):
 

Lib/test/test_sys.py

@@ -1064,7 +1064,7 @@ class SizeofTest(unittest.TestCase):
         # buffer
         # XXX
         # builtin_function_or_method
-        check(len, size('4P')) # XXX check layout
+        check(len, size('5P'))
         # bytearray
         samples = [b'', b'u'*100000]
         for sample in samples:
@@ -1095,7 +1095,7 @@ class SizeofTest(unittest.TestCase):
         # complex
         check(complex(0,1), size('2d'))
         # method_descriptor (descriptor object)
-        check(str.lower, size('3PP'))
+        check(str.lower, size('3PPP'))
         # classmethod_descriptor (descriptor object)
         # XXX
         # member_descriptor (descriptor object)
@@ -1164,7 +1164,7 @@ class SizeofTest(unittest.TestCase):
         check(x, vsize('5P2c4P3ic' + CO_MAXBLOCKS*'3i' + 'P' + extras*'P'))
         # function
         def func(): pass
-        check(func, size('12P'))
+        check(func, size('13P'))
         class c():
             @staticmethod
             def foo():
@@ -1259,7 +1259,7 @@ class SizeofTest(unittest.TestCase):
         check((1,2,3), vsize('') + 3*self.P)
         # type
         # static type: PyTypeObject
-        fmt = 'P2n15Pl4Pn9Pn11PIP'
+        fmt = 'P2nPI13Pl4Pn9Pn11PIPP'
         if hasattr(sys, 'getcounts'):
             fmt += '3n2P'
         s = vsize(fmt)

Misc/NEWS.d/next/C API/2019-05-22-15-24-08.bpo-36974.TkySRe.rst

@@ -0,0 +1,2 @@
+Implement :pep:`590`: Vectorcall: a fast calling protocol for CPython.
+This is a new protocol to optimize calls of custom callable objects.

Modules/_asynciomodule.c

@@ -367,8 +367,7 @@ call_soon(PyObject *loop, PyObject *func, PyObject *arg, PyObject *ctx)
         }
         stack[nargs] = (PyObject *)ctx;
 
-        handle = _PyObject_FastCallKeywords(
-            callable, stack, nargs, context_kwname);
+        handle = _PyObject_Vectorcall(callable, stack, nargs, context_kwname);
         Py_DECREF(callable);
     }
 
@@ -2805,8 +2804,7 @@ set_exception:
         PyObject *stack[2];
         stack[0] = wrapper;
         stack[1] = (PyObject *)task->task_context;
-        res = _PyObject_FastCallKeywords(
-            add_cb, stack, 1, context_kwname);
+        res = _PyObject_Vectorcall(add_cb, stack, 1, context_kwname);
         Py_DECREF(add_cb);
         Py_DECREF(wrapper);
         if (res == NULL) {

Modules/_testcapimodule.c

@@ -4713,7 +4713,7 @@ test_pyobject_fastcalldict(PyObject *self, PyObject *args)
 
 
 static PyObject *
-test_pyobject_fastcallkeywords(PyObject *self, PyObject *args)
+test_pyobject_vectorcall(PyObject *self, PyObject *args)
 {
     PyObject *func, *func_args, *kwnames = NULL;
     PyObject **stack;
@@ -4742,7 +4742,31 @@ test_pyobject_fastcallkeywords(PyObject *self, PyObject *args)
         PyErr_SetString(PyExc_TypeError, "kwnames must be None or a tuple");
         return NULL;
     }
-    return _PyObject_FastCallKeywords(func, stack, nargs, kwnames);
+    return _PyObject_Vectorcall(func, stack, nargs, kwnames);
+}
+
+
+static PyObject *
+test_pyvectorcall_call(PyObject *self, PyObject *args)
+{
+    PyObject *func;
+    PyObject *argstuple;
+    PyObject *kwargs = NULL;
+
+    if (!PyArg_ParseTuple(args, "OO|O", &func, &argstuple, &kwargs)) {
+        return NULL;
+    }
+
+    if (!PyTuple_Check(argstuple)) {
+        PyErr_SetString(PyExc_TypeError, "args must be a tuple");
+        return NULL;
+    }
+    if (kwargs != NULL && !PyDict_Check(kwargs)) {
+        PyErr_SetString(PyExc_TypeError, "kwargs must be a dict");
+        return NULL;
+    }
+
+    return PyVectorcall_Call(func, argstuple, kwargs);
 }
 
 
@@ -5230,7 +5254,8 @@ static PyMethodDef TestMethods[] = {
     {"raise_SIGINT_then_send_None", raise_SIGINT_then_send_None, METH_VARARGS},
     {"pyobject_fastcall", test_pyobject_fastcall, METH_VARARGS},
     {"pyobject_fastcalldict", test_pyobject_fastcalldict, METH_VARARGS},
-    {"pyobject_fastcallkeywords", test_pyobject_fastcallkeywords, METH_VARARGS},
+    {"pyobject_vectorcall", test_pyobject_vectorcall, METH_VARARGS},
+    {"pyvectorcall_call", test_pyvectorcall_call, METH_VARARGS},
     {"stack_pointer", stack_pointer, METH_NOARGS},
 #ifdef W_STOPCODE
     {"W_STOPCODE", py_w_stopcode, METH_VARARGS},

Objects/call.c

@@ -5,6 +5,10 @@
 #include "frameobject.h"
 
 
+static PyObject *
+cfunction_call_varargs(PyObject *func, PyObject *args, PyObject *kwargs);
+
+
 int
 _PyObject_HasFastCall(PyObject *callable)
 {
@@ -83,131 +87,132 @@ _Py_CheckFunctionResult(PyObject *callable, PyObject *result, const char *where)
 /* --- Core PyObject call functions ------------------------------- */
 
 PyObject *
-_PyObject_FastCallDict(PyObject *callable, PyObject *const *args, Py_ssize_t nargs,
-                       PyObject *kwargs)
+_PyObject_FastCallDict(PyObject *callable, PyObject *const *args,
+                       size_t nargsf, PyObject *kwargs)
 {
     /* _PyObject_FastCallDict() must not be called with an exception set,
        because it can clear it (directly or indirectly) and so the
        caller loses its exception */
     assert(!PyErr_Occurred());
-
     assert(callable != NULL);
+
+    Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
     assert(nargs >= 0);
     assert(nargs == 0 || args != NULL);
     assert(kwargs == NULL || PyDict_Check(kwargs));
 
-    if (PyFunction_Check(callable)) {
-        return _PyFunction_FastCallDict(callable, args, nargs, kwargs);
+    vectorcallfunc func = _PyVectorcall_Function(callable);
+    if (func == NULL) {
+        /* Use tp_call instead */
+        return _PyObject_MakeTpCall(callable, args, nargs, kwargs);
     }
-    else if (PyCFunction_Check(callable)) {
-        return _PyCFunction_FastCallDict(callable, args, nargs, kwargs);
+
+    PyObject *res;
+    if (kwargs == NULL) {
+        res = func(callable, args, nargsf, NULL);
     }
     else {
-        PyObject *argstuple, *result;
-        ternaryfunc call;
-
-        /* Slow-path: build a temporary tuple */
-        call = callable->ob_type->tp_call;
-        if (call == NULL) {
-            PyErr_Format(PyExc_TypeError, "'%.200s' object is not callable",
-                         callable->ob_type->tp_name);
+        PyObject *kwnames;
+        PyObject *const *newargs;
+        if (_PyStack_UnpackDict(args, nargs, kwargs, &newargs, &kwnames) < 0) {
             return NULL;
         }
-
-        argstuple = _PyTuple_FromArray(args, nargs);
-        if (argstuple == NULL) {
-            return NULL;
+        res = func(callable, newargs, nargs, kwnames);
+        if (kwnames != NULL) {
+            Py_ssize_t i, n = PyTuple_GET_SIZE(kwnames) + nargs;
+            for (i = 0; i < n; i++) {
+                Py_DECREF(newargs[i]);
+            }
+            PyMem_Free((PyObject **)newargs);
+            Py_DECREF(kwnames);
         }
-
-        if (Py_EnterRecursiveCall(" while calling a Python object")) {
-            Py_DECREF(argstuple);
-            return NULL;
-        }
-
-        result = (*call)(callable, argstuple, kwargs);
-
-        Py_LeaveRecursiveCall();
-        Py_DECREF(argstuple);
-
-        result = _Py_CheckFunctionResult(callable, result, NULL);
-        return result;
     }
+    return _Py_CheckFunctionResult(callable, res, NULL);
 }
 
 
 PyObject *
-_PyObject_FastCallKeywords(PyObject *callable, PyObject *const *stack, Py_ssize_t nargs,
-                           PyObject *kwnames)
+_PyObject_MakeTpCall(PyObject *callable, PyObject *const *args, Py_ssize_t nargs, PyObject *keywords)
 {
-    /* _PyObject_FastCallKeywords() must not be called with an exception set,
-       because it can clear it (directly or indirectly) and so the
-       caller loses its exception */
-    assert(!PyErr_Occurred());
+    /* Slow path: build a temporary tuple for positional arguments and a
+     * temporary dictionary for keyword arguments (if any) */
+    ternaryfunc call = Py_TYPE(callable)->tp_call;
+    if (call == NULL) {
+        PyErr_Format(PyExc_TypeError, "'%.200s' object is not callable",
+                     Py_TYPE(callable)->tp_name);
+        return NULL;
+    }
 
     assert(nargs >= 0);
-    assert(kwnames == NULL || PyTuple_CheckExact(kwnames));
-
-    /* kwnames must only contains str strings, no subclass, and all keys must
-       be unique: these checks are implemented in Python/ceval.c and
-       _PyArg_ParseStackAndKeywords(). */
-
-    if (PyFunction_Check(callable)) {
-        return _PyFunction_FastCallKeywords(callable, stack, nargs, kwnames);
+    assert(nargs == 0 || args != NULL);
+    assert(keywords == NULL || PyTuple_Check(keywords) || PyDict_Check(keywords));
+    PyObject *argstuple = _PyTuple_FromArray(args, nargs);
+    if (argstuple == NULL) {
+        return NULL;
     }
-    if (PyCFunction_Check(callable)) {
-        return _PyCFunction_FastCallKeywords(callable, stack, nargs, kwnames);
+
+    PyObject *kwdict;
+    if (keywords == NULL || PyDict_Check(keywords)) {
+        kwdict = keywords;
     }
     else {
-        /* Slow-path: build a temporary tuple for positional arguments and a
-           temporary dictionary for keyword arguments (if any) */
-
-        ternaryfunc call;
-        PyObject *argstuple;
-        PyObject *kwdict, *result;
-        Py_ssize_t nkwargs;
-
-        nkwargs = (kwnames == NULL) ? 0 : PyTuple_GET_SIZE(kwnames);
-        assert((nargs == 0 && nkwargs == 0) || stack != NULL);
-
-        call = callable->ob_type->tp_call;
-        if (call == NULL) {
-            PyErr_Format(PyExc_TypeError, "'%.200s' object is not callable",
-                         callable->ob_type->tp_name);
-            return NULL;
-        }
-
-        argstuple = _PyTuple_FromArray(stack, nargs);
-        if (argstuple == NULL) {
-            return NULL;
-        }
-
-        if (nkwargs > 0) {
-            kwdict = _PyStack_AsDict(stack + nargs, kwnames);
+        if (PyTuple_GET_SIZE(keywords)) {
+            assert(args != NULL);
+            kwdict = _PyStack_AsDict(args + nargs, keywords);
             if (kwdict == NULL) {
                 Py_DECREF(argstuple);
                 return NULL;
             }
         }
         else {
-            kwdict = NULL;
+            keywords = kwdict = NULL;
         }
-
-        if (Py_EnterRecursiveCall(" while calling a Python object")) {
-            Py_DECREF(argstuple);
-            Py_XDECREF(kwdict);
-            return NULL;
-        }
-
-        result = (*call)(callable, argstuple, kwdict);
-
-        Py_LeaveRecursiveCall();
-
-        Py_DECREF(argstuple);
-        Py_XDECREF(kwdict);
-
-        result = _Py_CheckFunctionResult(callable, result, NULL);
-        return result;
     }
+
+    PyObject *result = NULL;
+    if (Py_EnterRecursiveCall(" while calling a Python object") == 0)
+    {
+        result = call(callable, argstuple, kwdict);
+        Py_LeaveRecursiveCall();
+    }
+
+    Py_DECREF(argstuple);
+    if (kwdict != keywords) {
+        Py_DECREF(kwdict);
+    }
+
+    result = _Py_CheckFunctionResult(callable, result, NULL);
+    return result;
+}
+
+
+PyObject *
+PyVectorcall_Call(PyObject *callable, PyObject *tuple, PyObject *kwargs)
+{
+    vectorcallfunc func = _PyVectorcall_Function(callable);
+    if (func == NULL) {
+        PyErr_Format(PyExc_TypeError, "'%.200s' object does not support vectorcall",
+                     Py_TYPE(callable)->tp_name);
+        return NULL;
+    }
+    PyObject *const *args;
+    Py_ssize_t nargs = PyTuple_GET_SIZE(tuple);
+    PyObject *kwnames;
+    if (_PyStack_UnpackDict(_PyTuple_ITEMS(tuple), nargs,
+        kwargs, &args, &kwnames) < 0) {
+        return NULL;
+    }
+    PyObject *result = func(callable, args, nargs, kwnames);
+    if (kwnames != NULL) {
+        Py_ssize_t i, n = PyTuple_GET_SIZE(kwnames) + nargs;
+        for (i = 0; i < n; i++) {
+            Py_DECREF(args[i]);
+        }
+        PyMem_Free((PyObject **)args);
+        Py_DECREF(kwnames);
+    }
+
+    return result;
 }
 
 
@@ -224,14 +229,13 @@ PyObject_Call(PyObject *callable, PyObject *args, PyObject *kwargs)
     assert(PyTuple_Check(args));
     assert(kwargs == NULL || PyDict_Check(kwargs));
 
-    if (PyFunction_Check(callable)) {
-        return _PyFunction_FastCallDict(callable,
-                                        _PyTuple_ITEMS(args),
-                                        PyTuple_GET_SIZE(args),
-                                        kwargs);
+    if (_PyVectorcall_Function(callable) != NULL) {
+        return PyVectorcall_Call(callable, args, kwargs);
     }
     else if (PyCFunction_Check(callable)) {
-        return PyCFunction_Call(callable, args, kwargs);
+        /* This must be a METH_VARARGS function, otherwise we would be
+         * in the previous case */
+        return cfunction_call_varargs(callable, args, kwargs);
     }
     else {
         call = callable->ob_type->tp_call;
@@ -384,9 +388,10 @@ _PyFunction_FastCallDict(PyObject *func, PyObject *const *args, Py_ssize_t nargs
     return result;
 }
 
+
 PyObject *
-_PyFunction_FastCallKeywords(PyObject *func, PyObject *const *stack,
-                             Py_ssize_t nargs, PyObject *kwnames)
+_PyFunction_FastCallKeywords(PyObject *func, PyObject* const* stack,
+                             size_t nargsf, PyObject *kwnames)
 {
     PyCodeObject *co = (PyCodeObject *)PyFunction_GET_CODE(func);
     PyObject *globals = PyFunction_GET_GLOBALS(func);
@@ -397,6 +402,7 @@ _PyFunction_FastCallKeywords(PyObject *func, PyObject *const *stack,
     Py_ssize_t nd;
 
     assert(PyFunction_Check(func));
+    Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
     assert(nargs >= 0);
     assert(kwnames == NULL || PyTuple_CheckExact(kwnames));
     assert((nargs == 0 && nkwargs == 0) || stack != NULL);
@@ -725,13 +731,14 @@ exit:
 
 PyObject *
 _PyCFunction_FastCallKeywords(PyObject *func,
-                              PyObject *const *args, Py_ssize_t nargs,
+                              PyObject *const *args, size_t nargsf,
                               PyObject *kwnames)
 {
     PyObject *result;
 
     assert(func != NULL);
     assert(PyCFunction_Check(func));
+    Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
 
     result = _PyMethodDef_RawFastCallKeywords(((PyCFunctionObject*)func)->m_ml,
                                               PyCFunction_GET_SELF(func),
@@ -751,6 +758,7 @@ cfunction_call_varargs(PyObject *func, PyObject *args, PyObject *kwargs)
     PyObject *self = PyCFunction_GET_SELF(func);
     PyObject *result;
 
+    assert(PyCFunction_GET_FLAGS(func) & METH_VARARGS);
     if (PyCFunction_GET_FLAGS(func) & METH_KEYWORDS) {
         if (Py_EnterRecursiveCall(" while calling a Python object")) {
             return NULL;
@@ -783,18 +791,12 @@ cfunction_call_varargs(PyObject *func, PyObject *args, PyObject *kwargs)
 PyObject *
 PyCFunction_Call(PyObject *func, PyObject *args, PyObject *kwargs)
 {
-    /* first try METH_VARARGS to pass directly args tuple unchanged.
-       _PyMethodDef_RawFastCallDict() creates a new temporary tuple
-       for METH_VARARGS. */
+    /* For METH_VARARGS, we cannot use vectorcall as the vectorcall pointer
+     * is NULL. This is intentional, since vectorcall would be slower. */
     if (PyCFunction_GET_FLAGS(func) & METH_VARARGS) {
         return cfunction_call_varargs(func, args, kwargs);
     }
-    else {
-        return _PyCFunction_FastCallDict(func,
-                                         _PyTuple_ITEMS(args),
-                                         PyTuple_GET_SIZE(args),
-                                         kwargs);
-    }
+    return PyVectorcall_Call(func, args, kwargs);
 }
 
 

Objects/classobject.c

@@ -40,6 +40,45 @@ PyMethod_Self(PyObject *im)
     return ((PyMethodObject *)im)->im_self;
 }
 
+
+static PyObject *
+method_vectorcall(PyObject *method, PyObject *const *args,
+                  size_t nargsf, PyObject *kwnames)
+{
+    assert(Py_TYPE(method) == &PyMethod_Type);
+    PyObject *self, *func, *result;
+    self = PyMethod_GET_SELF(method);
+    func = PyMethod_GET_FUNCTION(method);
+    Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
+
+    if (nargsf & PY_VECTORCALL_ARGUMENTS_OFFSET) {
+        /* PY_VECTORCALL_ARGUMENTS_OFFSET is set, so we are allowed to mutate the vector */
+        PyObject **newargs = (PyObject**)args - 1;
+        nargs += 1;
+        PyObject *tmp = newargs[0];
+        newargs[0] = self;
+        result = _PyObject_Vectorcall(func, newargs, nargs, kwnames);
+        newargs[0] = tmp;
+    }
+    else {
+        Py_ssize_t nkwargs = (kwnames == NULL) ? 0 : PyTuple_GET_SIZE(kwnames);
+        PyObject **newargs;
+        Py_ssize_t totalargs = nargs + nkwargs;
+        newargs = PyMem_Malloc((totalargs+1) * sizeof(PyObject *));
+        if (newargs == NULL) {
+            PyErr_NoMemory();
+            return NULL;
+        }
+        /* use borrowed references */
+        newargs[0] = self;
+        memcpy(newargs + 1, args, totalargs * sizeof(PyObject *));
+        result = _PyObject_Vectorcall(func, newargs, nargs+1, kwnames);
+        PyMem_Free(newargs);
+    }
+    return result;
+}
+
+
 /* Method objects are used for bound instance methods returned by
    instancename.methodname. ClassName.methodname returns an ordinary
    function.
@@ -69,6 +108,7 @@ PyMethod_New(PyObject *func, PyObject *self)
     im->im_func = func;
     Py_XINCREF(self);
     im->im_self = self;
+    im->vectorcall = method_vectorcall;
     _PyObject_GC_TRACK(im);
     return (PyObject *)im;
 }
@@ -309,7 +349,7 @@ PyTypeObject PyMethod_Type = {
     sizeof(PyMethodObject),
     0,
     (destructor)method_dealloc,                 /* tp_dealloc */
-    0,                                          /* tp_print */
+    offsetof(PyMethodObject, vectorcall),       /* tp_vectorcall_offset */
     0,                                          /* tp_getattr */
     0,                                          /* tp_setattr */
     0,                                          /* tp_reserved */
@@ -323,7 +363,8 @@ PyTypeObject PyMethod_Type = {
     method_getattro,                            /* tp_getattro */
     PyObject_GenericSetAttr,                    /* 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_VECTORCALL,                /* tp_flags */
     method_doc,                                 /* tp_doc */
     (traverseproc)method_traverse,              /* tp_traverse */
     0,                                          /* tp_clear */

Objects/descrobject.c

@@ -265,13 +265,14 @@ methoddescr_call(PyMethodDescrObject *descr, PyObject *args, PyObject *kwargs)
 // same to methoddescr_call(), but use FASTCALL convention.
 PyObject *
 _PyMethodDescr_FastCallKeywords(PyObject *descrobj,
-                                PyObject *const *args, Py_ssize_t nargs,
+                                PyObject *const *args, size_t nargsf,
                                 PyObject *kwnames)
 {
     assert(Py_TYPE(descrobj) == &PyMethodDescr_Type);
     PyMethodDescrObject *descr = (PyMethodDescrObject *)descrobj;
     PyObject *self, *result;
 
+    Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
     /* Make sure that the first argument is acceptable as 'self' */
     if (nargs < 1) {
         PyErr_Format(PyExc_TypeError,
@@ -542,7 +543,7 @@ PyTypeObject PyMethodDescr_Type = {
     sizeof(PyMethodDescrObject),
     0,
     (destructor)descr_dealloc,                  /* tp_dealloc */
-    0,                                          /* tp_print */
+    offsetof(PyMethodDescrObject, vectorcall),  /* tp_vectorcall_offset */
     0,                                          /* tp_getattr */
     0,                                          /* tp_setattr */
     0,                                          /* tp_reserved */
@@ -557,6 +558,7 @@ PyTypeObject PyMethodDescr_Type = {
     0,                                          /* tp_setattro */
     0,                                          /* tp_as_buffer */
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+    _Py_TPFLAGS_HAVE_VECTORCALL |
     Py_TPFLAGS_METHOD_DESCRIPTOR,               /* tp_flags */
     0,                                          /* tp_doc */
     descr_traverse,                             /* tp_traverse */
@@ -752,8 +754,10 @@ PyDescr_NewMethod(PyTypeObject *type, PyMethodDef *method)
 
     descr = (PyMethodDescrObject *)descr_new(&PyMethodDescr_Type,
                                              type, method->ml_name);
-    if (descr != NULL)
+    if (descr != NULL) {
         descr->d_method = method;
+        descr->vectorcall = &_PyMethodDescr_FastCallKeywords;
+    }
     return (PyObject *)descr;
 }
 

Objects/funcobject.c

@@ -36,6 +36,7 @@ PyFunction_NewWithQualName(PyObject *code, PyObject *globals, PyObject *qualname
     op->func_defaults = NULL; /* No default arguments */
     op->func_kwdefaults = NULL; /* No keyword only defaults */
     op->func_closure = NULL;
+    op->vectorcall = _PyFunction_FastCallKeywords;
 
     consts = ((PyCodeObject *)code)->co_consts;
     if (PyTuple_Size(consts) >= 1) {
@@ -649,7 +650,7 @@ PyTypeObject PyFunction_Type = {
     sizeof(PyFunctionObject),
     0,
     (destructor)func_dealloc,                   /* tp_dealloc */
-    0,                                          /* tp_print */
+    offsetof(PyFunctionObject, vectorcall),     /* tp_vectorcall_offset */
     0,                                          /* tp_getattr */
     0,                                          /* tp_setattr */
     0,                                          /* tp_reserved */
@@ -664,6 +665,7 @@ PyTypeObject PyFunction_Type = {
     0,                                          /* tp_setattro */
     0,                                          /* tp_as_buffer */
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+    _Py_TPFLAGS_HAVE_VECTORCALL |
     Py_TPFLAGS_METHOD_DESCRIPTOR,               /* tp_flags */
     func_new__doc__,                            /* tp_doc */
     (traverseproc)func_traverse,                /* tp_traverse */

Objects/methodobject.c

@@ -46,6 +46,14 @@ PyCFunction_NewEx(PyMethodDef *ml, PyObject *self, PyObject *module)
     op->m_self = self;
     Py_XINCREF(module);
     op->m_module = module;
+    if (ml->ml_flags & METH_VARARGS) {
+        /* For METH_VARARGS functions, it's more efficient to use tp_call
+         * instead of vectorcall. */
+        op->vectorcall = NULL;
+    }
+    else {
+        op->vectorcall = &_PyCFunction_FastCallKeywords;
+    }
     _PyObject_GC_TRACK(op);
     return (PyObject *)op;
 }
@@ -264,7 +272,7 @@ PyTypeObject PyCFunction_Type = {
     sizeof(PyCFunctionObject),
     0,
     (destructor)meth_dealloc,                   /* tp_dealloc */
-    0,                                          /* tp_print */
+    offsetof(PyCFunctionObject, vectorcall),    /* tp_vectorcall_offset */
     0,                                          /* tp_getattr */
     0,                                          /* tp_setattr */
     0,                                          /* tp_reserved */
@@ -278,7 +286,8 @@ PyTypeObject PyCFunction_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_VECTORCALL,                /* tp_flags */
     0,                                          /* tp_doc */
     (traverseproc)meth_traverse,                /* tp_traverse */
     0,                                          /* tp_clear */

Python/bltinmodule.c

@@ -483,7 +483,7 @@ builtin_breakpoint(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyOb
         return NULL;
     }
     Py_INCREF(hook);
-    PyObject *retval = _PyObject_FastCallKeywords(hook, args, nargs, keywords);
+    PyObject *retval = _PyObject_Vectorcall(hook, args, nargs, keywords);
     Py_DECREF(hook);
     return retval;
 }
@@ -2231,7 +2231,7 @@ builtin_sorted(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyObject
     }
 
     assert(nargs >= 1);
-    v = _PyObject_FastCallKeywords(callable, args + 1, nargs - 1, kwnames);
+    v = _PyObject_Vectorcall(callable, args + 1, nargs - 1, kwnames);
     Py_DECREF(callable);
     if (v == NULL) {
         Py_DECREF(newlist);

Python/ceval.c

@@ -4806,6 +4806,40 @@ if (tstate->use_tracing && tstate->c_profilefunc) { \
     x = call; \
     }
 
+
+static PyObject *
+trace_call_function(PyThreadState *tstate,
+                    PyObject *func,
+                    PyObject **args, Py_ssize_t nargs,
+                    PyObject *kwnames)
+{
+    PyObject *x;
+    if (PyCFunction_Check(func)) {
+        C_TRACE(x, _PyCFunction_FastCallKeywords(func, args, nargs, kwnames));
+        return x;
+    }
+    else if (Py_TYPE(func) == &PyMethodDescr_Type && nargs > 0) {
+        /* We need to create a temporary bound method as argument
+           for profiling.
+
+           If nargs == 0, then this cannot work because we have no
+           "self". In any case, the call itself would raise
+           TypeError (foo needs an argument), so we just skip
+           profiling. */
+        PyObject *self = args[0];
+        func = Py_TYPE(func)->tp_descr_get(func, self, (PyObject*)Py_TYPE(self));
+        if (func == NULL) {
+            return NULL;
+        }
+        C_TRACE(x, _PyCFunction_FastCallKeywords(func,
+                                                 args+1, nargs-1,
+                                                 kwnames));
+        Py_DECREF(func);
+        return x;
+    }
+    return _PyObject_Vectorcall(func, args, nargs | PY_VECTORCALL_ARGUMENTS_OFFSET, kwnames);
+}
+
 /* Issue #29227: Inline call_function() into _PyEval_EvalFrameDefault()
    to reduce the stack consumption. */
 Py_LOCAL_INLINE(PyObject *) _Py_HOT_FUNCTION
@@ -4818,63 +4852,11 @@ call_function(PyThreadState *tstate, PyObject ***pp_stack, Py_ssize_t oparg, PyO
     Py_ssize_t nargs = oparg - nkwargs;
     PyObject **stack = (*pp_stack) - nargs - nkwargs;
 
-    /* Always dispatch PyCFunction first, because these are
-       presumed to be the most frequent callable object.
-    */
-    if (PyCFunction_Check(func)) {
-        C_TRACE(x, _PyCFunction_FastCallKeywords(func, stack, nargs, kwnames));
-    }
-    else if (Py_TYPE(func) == &PyMethodDescr_Type) {
-        if (nargs > 0 && tstate->use_tracing) {
-            /* We need to create a temporary bound method as argument
-               for profiling.
-
-               If nargs == 0, then this cannot work because we have no
-               "self". In any case, the call itself would raise
-               TypeError (foo needs an argument), so we just skip
-               profiling. */
-            PyObject *self = stack[0];
-            func = Py_TYPE(func)->tp_descr_get(func, self, (PyObject*)Py_TYPE(self));
-            if (func != NULL) {
-                C_TRACE(x, _PyCFunction_FastCallKeywords(func,
-                                                         stack+1, nargs-1,
-                                                         kwnames));
-                Py_DECREF(func);
-            }
-            else {
-                x = NULL;
-            }
-        }
-        else {
-            x = _PyMethodDescr_FastCallKeywords(func, stack, nargs, kwnames);
-        }
+    if (tstate->use_tracing) {
+        x = trace_call_function(tstate, func, stack, nargs, kwnames);
     }
     else {
-        if (PyMethod_Check(func) && PyMethod_GET_SELF(func) != NULL) {
-            /* Optimize access to bound methods. Reuse the Python stack
-               to pass 'self' as the first argument, replace 'func'
-               with 'self'. It avoids the creation of a new temporary tuple
-               for arguments (to replace func with self) when the method uses
-               FASTCALL. */
-            PyObject *self = PyMethod_GET_SELF(func);
-            Py_INCREF(self);
-            func = PyMethod_GET_FUNCTION(func);
-            Py_INCREF(func);
-            Py_SETREF(*pfunc, self);
-            nargs++;
-            stack--;
-        }
-        else {
-            Py_INCREF(func);
-        }
-
-        if (PyFunction_Check(func)) {
-            x = _PyFunction_FastCallKeywords(func, stack, nargs, kwnames);
-        }
-        else {
-            x = _PyObject_FastCallKeywords(func, stack, nargs, kwnames);
-        }
-        Py_DECREF(func);
+        x = _PyObject_Vectorcall(func, stack, nargs | PY_VECTORCALL_ARGUMENTS_OFFSET, kwnames);
     }
 
     assert((x != NULL) ^ (_PyErr_Occurred(tstate) != NULL));

Python/context.c

@@ -631,7 +631,7 @@ context_run(PyContext *self, PyObject *const *args,
         return NULL;
     }
 
-    PyObject *call_result = _PyObject_FastCallKeywords(
+    PyObject *call_result = _PyObject_Vectorcall(
         args[0], args + 1, nargs - 1, kwnames);
 
     if (PyContext_Exit((PyObject *)self)) {

Python/sysmodule.c

@@ -481,7 +481,7 @@ sys_breakpointhook(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyOb
         return NULL;
     }
     PyMem_RawFree(envar);
-    PyObject *retval = _PyObject_FastCallKeywords(hook, args, nargs, keywords);
+    PyObject *retval = _PyObject_Vectorcall(hook, args, nargs, keywords);
     Py_DECREF(hook);
     return retval;