bpo-37151: remove special case for PyCFunction from PyObject_Call (GH-14684)

bpo-37151: remove special case for PyCFunction from PyObject_Call

Alse, make the undocumented function PyCFunction_Call an alias
of PyObject_Call and deprecate it.

Include/methodobject.h

@@ -39,7 +39,7 @@ PyAPI_FUNC(int) PyCFunction_GetFlags(PyObject *);
 #define PyCFunction_GET_FLAGS(func) \
         (((PyCFunctionObject *)func) -> m_ml -> ml_flags)
 #endif
-PyAPI_FUNC(PyObject *) PyCFunction_Call(PyObject *, PyObject *, PyObject *);
+Py_DEPRECATED(3.9) PyAPI_FUNC(PyObject *) PyCFunction_Call(PyObject *, PyObject *, PyObject *);
 
 struct PyMethodDef {
     const char  *ml_name;   /* The name of the built-in function/method */

Misc/NEWS.d/next/C API/2019-07-16-11-02-00.bpo-37151.YKfuNA.rst

+``PyCFunction_Call`` is now a deprecated alias of :c:func:`PyObject_Call`.

Objects/call.c

@@ -5,9 +5,6 @@
 #include "frameobject.h"
 
 
-static PyObject *
-cfunction_call_varargs(PyObject *func, PyObject *args, PyObject *kwargs);
-
 static PyObject *const *
 _PyStack_UnpackDict(PyObject *const *args, Py_ssize_t nargs, PyObject *kwargs,
                     PyObject **p_kwnames);
@@ -236,11 +233,6 @@ PyObject_Call(PyObject *callable, PyObject *args, PyObject *kwargs)
     if (_PyVectorcall_Function(callable) != NULL) {
         return PyVectorcall_Call(callable, args, kwargs);
     }
-    else if (PyCFunction_Check(callable)) {
-        /* 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;
         if (call == NULL) {
@@ -261,6 +253,13 @@ PyObject_Call(PyObject *callable, PyObject *args, PyObject *kwargs)
 }
 
 
+PyObject *
+PyCFunction_Call(PyObject *callable, PyObject *args, PyObject *kwargs)
+{
+    return PyObject_Call(callable, args, kwargs);
+}
+
+
 /* --- PyFunction call functions ---------------------------------- */
 
 static PyObject* _Py_HOT_FUNCTION
@@ -363,60 +362,6 @@ _PyFunction_Vectorcall(PyObject *func, PyObject* const* stack,
 }
 
 
-/* --- PyCFunction call functions --------------------------------- */
-
-static PyObject *
-cfunction_call_varargs(PyObject *func, PyObject *args, PyObject *kwargs)
-{
-    assert(!PyErr_Occurred());
-    assert(kwargs == NULL || PyDict_Check(kwargs));
-
-    PyCFunction meth = PyCFunction_GET_FUNCTION(func);
-    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;
-        }
-
-        result = (*(PyCFunctionWithKeywords)(void(*)(void))meth)(self, args, kwargs);
-
-        Py_LeaveRecursiveCall();
-    }
-    else {
-        if (kwargs != NULL && PyDict_GET_SIZE(kwargs) != 0) {
-            PyErr_Format(PyExc_TypeError, "%.200s() takes no keyword arguments",
-                         ((PyCFunctionObject*)func)->m_ml->ml_name);
-            return NULL;
-        }
-
-        if (Py_EnterRecursiveCall(" while calling a Python object")) {
-            return NULL;
-        }
-
-        result = (*meth)(self, args);
-
-        Py_LeaveRecursiveCall();
-    }
-
-    return _Py_CheckFunctionResult(func, result, NULL);
-}
-
-
-PyObject *
-PyCFunction_Call(PyObject *func, PyObject *args, PyObject *kwargs)
-{
-    /* 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);
-    }
-    return PyVectorcall_Call(func, args, kwargs);
-}
-
-
 /* --- More complex call functions -------------------------------- */
 
 /* External interface to call any callable object.

Objects/methodobject.c

@@ -19,6 +19,8 @@ static PyObject * cfunction_vectorcall_NOARGS(
     PyObject *func, PyObject *const *args, size_t nargsf, PyObject *kwnames);
 static PyObject * cfunction_vectorcall_O(
     PyObject *func, PyObject *const *args, size_t nargsf, PyObject *kwnames);
+static PyObject * cfunction_call(
+    PyObject *func, PyObject *args, PyObject *kwargs);
 
 
 PyObject *
@@ -289,7 +291,7 @@ PyTypeObject PyCFunction_Type = {
     0,                                          /* tp_as_sequence */
     0,                                          /* tp_as_mapping */
     (hashfunc)meth_hash,                        /* tp_hash */
-    PyCFunction_Call,                           /* tp_call */
+    cfunction_call,                             /* tp_call */
     0,                                          /* tp_str */
     PyObject_GenericGetAttr,                    /* tp_getattro */
     0,                                          /* tp_setattro */
@@ -441,3 +443,36 @@ cfunction_vectorcall_O(
     Py_LeaveRecursiveCall();
     return result;
 }
+
+
+static PyObject *
+cfunction_call(PyObject *func, PyObject *args, PyObject *kwargs)
+{
+    assert(!PyErr_Occurred());
+    assert(kwargs == NULL || PyDict_Check(kwargs));
+
+    int flags = PyCFunction_GET_FLAGS(func);
+    if (!(flags & METH_VARARGS)) {
+        /* If this is not a METH_VARARGS function, delegate to vectorcall */
+        return PyVectorcall_Call(func, args, kwargs);
+    }
+
+    /* For METH_VARARGS, we cannot use vectorcall as the vectorcall pointer
+     * is NULL. This is intentional, since vectorcall would be slower. */
+    PyCFunction meth = PyCFunction_GET_FUNCTION(func);
+    PyObject *self = PyCFunction_GET_SELF(func);
+
+    PyObject *result;
+    if (flags & METH_KEYWORDS) {
+        result = (*(PyCFunctionWithKeywords)(void(*)(void))meth)(self, args, kwargs);
+    }
+    else {
+        if (kwargs != NULL && PyDict_GET_SIZE(kwargs) != 0) {
+            PyErr_Format(PyExc_TypeError, "%.200s() takes no keyword arguments",
+                         ((PyCFunctionObject*)func)->m_ml->ml_name);
+            return NULL;
+        }
+        result = meth(self, args);
+    }
+    return _Py_CheckFunctionResult(func, result, NULL);
+}

Python/ceval.c

@@ -5001,7 +5001,7 @@ do_call_core(PyThreadState *tstate, PyObject *func, PyObject *callargs, PyObject
     PyObject *result;
 
     if (PyCFunction_Check(func)) {
-        C_TRACE(result, PyCFunction_Call(func, callargs, kwdict));
+        C_TRACE(result, PyObject_Call(func, callargs, kwdict));
         return result;
     }
     else if (Py_TYPE(func) == &PyMethodDescr_Type) {

Tools/gdb/libpython.py

@@ -1564,7 +1564,7 @@ class Frame(object):
             return False
 
         if (caller.startswith('cfunction_vectorcall_') or
-            caller == 'cfunction_call_varargs'):
+            caller == 'cfunction_call'):
             arg_name = 'func'
             # Within that frame:
             #   "func" is the local containing the PyObject* of the