gh-114626: add PyCFunctionFast and PyCFunctionFastWithKeywords (GH-114627)

Co-authored-by: Petr Viktorin <[email protected]>

Author: davidhewitt

Doc/c-api/structures.rst

@@ -187,26 +187,26 @@ Implementing functions and methods
                                         PyObject *kwargs);
 
 
-.. c:type:: _PyCFunctionFast
+.. c:type:: PyCFunctionFast
 
    Type of the functions used to implement Python callables in C
    with signature :c:macro:`METH_FASTCALL`.
    The function signature is::
 
-      PyObject *_PyCFunctionFast(PyObject *self,
-                                 PyObject *const *args,
-                                 Py_ssize_t nargs);
+      PyObject *PyCFunctionFast(PyObject *self,
+                                PyObject *const *args,
+                                Py_ssize_t nargs);
 
-.. c:type:: _PyCFunctionFastWithKeywords
+.. c:type:: PyCFunctionFastWithKeywords
 
    Type of the functions used to implement Python callables in C
    with signature :ref:`METH_FASTCALL | METH_KEYWORDS <METH_FASTCALL-METH_KEYWORDS>`.
    The function signature is::
 
-      PyObject *_PyCFunctionFastWithKeywords(PyObject *self,
-                                             PyObject *const *args,
-                                             Py_ssize_t nargs,
-                                             PyObject *kwnames);
+      PyObject *PyCFunctionFastWithKeywords(PyObject *self,
+                                            PyObject *const *args,
+                                            Py_ssize_t nargs,
+                                            PyObject *kwnames);
 
 .. c:type:: PyCMethod
 
@@ -290,7 +290,7 @@ There are these calling conventions:
 .. c:macro:: METH_FASTCALL
 
    Fast calling convention supporting only positional arguments.
-   The methods have the type :c:type:`_PyCFunctionFast`.
+   The methods have the type :c:type:`PyCFunctionFast`.
    The first parameter is *self*, the second parameter is a C array
    of :c:expr:`PyObject*` values indicating the arguments and the third
    parameter is the number of arguments (the length of the array).
@@ -306,7 +306,7 @@ There are these calling conventions:
 
 :c:expr:`METH_FASTCALL | METH_KEYWORDS`
    Extension of :c:macro:`METH_FASTCALL` supporting also keyword arguments,
-   with methods of type :c:type:`_PyCFunctionFastWithKeywords`.
+   with methods of type :c:type:`PyCFunctionFastWithKeywords`.
    Keyword arguments are passed the same way as in the
    :ref:`vectorcall protocol <vectorcall>`:
    there is an additional fourth :c:expr:`PyObject*` parameter

Doc/data/stable_abi.dat

@@ -17,15 +17,22 @@ PyAPI_DATA(PyTypeObject) PyCFunction_Type;
 #define PyCFunction_Check(op) PyObject_TypeCheck((op), &PyCFunction_Type)
 
 typedef PyObject *(*PyCFunction)(PyObject *, PyObject *);
-typedef PyObject *(*_PyCFunctionFast) (PyObject *, PyObject *const *, Py_ssize_t);
+typedef PyObject *(*PyCFunctionFast) (PyObject *, PyObject *const *, Py_ssize_t);
 typedef PyObject *(*PyCFunctionWithKeywords)(PyObject *, PyObject *,
                                              PyObject *);
-typedef PyObject *(*_PyCFunctionFastWithKeywords) (PyObject *,
-                                                   PyObject *const *, Py_ssize_t,
-                                                   PyObject *);
+typedef PyObject *(*PyCFunctionFastWithKeywords) (PyObject *,
+                                                  PyObject *const *, Py_ssize_t,
+                                                  PyObject *);
 typedef PyObject *(*PyCMethod)(PyObject *, PyTypeObject *, PyObject *const *,
                                size_t, PyObject *);
 
+// For backwards compatibility. `METH_FASTCALL` was added to the stable API in
+// 3.10 alongside `_PyCFunctionFastWithKeywords` and `_PyCFunctionFast`.
+// Note that the underscore-prefixed names were documented in public docs;
+// people may be using them.
+typedef PyCFunctionFast _PyCFunctionFast;
+typedef PyCFunctionWithKeywords _PyCFunctionWithKeywords;
+
 // Cast an function to the PyCFunction type to use it with PyMethodDef.
 //
 // This macro can be used to prevent compiler warnings if the first parameter

Include/methodobject.h

@@ -0,0 +1 @@
+Add ``PyCFunctionFast`` and ``PyCFunctionFastWithKeywords`` typedefs (identical to the existing ``_PyCFunctionFast`` and ``_PyCFunctionFastWithKeywords`` typedefs, just without a leading ``_`` prefix).

Misc/NEWS.d/next/C API/2024-01-26-21-54-42.gh-issue-114626.SKhbh_.rst

@@ -2489,3 +2489,10 @@
     added = '3.13'
 [function.PyList_GetItemRef]
     added = '3.13'
+[typedef.PyCFunctionFast]
+    added = '3.13'
+    # "abi-only" since 3.10.  (Callback type names aren't used in C code,
+    # but this function signature was expected with METH_FASTCALL.)
+[typedef.PyCFunctionFastWithKeywords]
+    added = '3.13'
+    # "abi-only" since 3.10.  (Same story as PyCFunctionFast.)

Misc/stable_abi.toml

@@ -393,7 +393,7 @@ method_vectorcall_FASTCALL(
     if (method_check_args(func, args, nargs, kwnames)) {
         return NULL;
     }
-    _PyCFunctionFast meth = (_PyCFunctionFast)
+    PyCFunctionFast meth = (PyCFunctionFast)
                             method_enter_call(tstate, func);
     if (meth == NULL) {
         return NULL;
@@ -412,7 +412,7 @@ method_vectorcall_FASTCALL_KEYWORDS(
     if (method_check_args(func, args, nargs, NULL)) {
         return NULL;
     }
-    _PyCFunctionFastWithKeywords meth = (_PyCFunctionFastWithKeywords)
+    PyCFunctionFastWithKeywords meth = (PyCFunctionFastWithKeywords)
                                         method_enter_call(tstate, func);
     if (meth == NULL) {
         return NULL;

Objects/descrobject.c

@@ -417,7 +417,7 @@ cfunction_vectorcall_FASTCALL(
         return NULL;
     }
     Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
-    _PyCFunctionFast meth = (_PyCFunctionFast)
+    PyCFunctionFast meth = (PyCFunctionFast)
                             cfunction_enter_call(tstate, func);
     if (meth == NULL) {
         return NULL;
@@ -433,7 +433,7 @@ cfunction_vectorcall_FASTCALL_KEYWORDS(
 {
     PyThreadState *tstate = _PyThreadState_GET();
     Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
-    _PyCFunctionFastWithKeywords meth = (_PyCFunctionFastWithKeywords)
+    PyCFunctionFastWithKeywords meth = (PyCFunctionFastWithKeywords)
                                         cfunction_enter_call(tstate, func);
     if (meth == NULL) {
         return NULL;
@@ -552,4 +552,3 @@ cfunction_call(PyObject *func, PyObject *args, PyObject *kwargs)
     }
     return _Py_CheckFunctionResult(tstate, func, result, NULL);
 }
-

Objects/methodobject.c

@@ -3376,7 +3376,7 @@ dummy_func(
             STAT_INC(CALL, hit);
             PyCFunction cfunc = PyCFunction_GET_FUNCTION(callable);
             /* res = func(self, args, nargs) */
-            res = ((_PyCFunctionFast)(void(*)(void))cfunc)(
+            res = ((PyCFunctionFast)(void(*)(void))cfunc)(
                 PyCFunction_GET_SELF(callable),
                 args,
                 total_args);
@@ -3407,8 +3407,8 @@ dummy_func(
             DEOPT_IF(PyCFunction_GET_FLAGS(callable) != (METH_FASTCALL | METH_KEYWORDS));
             STAT_INC(CALL, hit);
             /* res = func(self, args, nargs, kwnames) */
-            _PyCFunctionFastWithKeywords cfunc =
-                (_PyCFunctionFastWithKeywords)(void(*)(void))
+            PyCFunctionFastWithKeywords cfunc =
+                (PyCFunctionFastWithKeywords)(void(*)(void))
                 PyCFunction_GET_FUNCTION(callable);
             res = cfunc(PyCFunction_GET_SELF(callable), args, total_args, NULL);
             assert((res != NULL) ^ (_PyErr_Occurred(tstate) != NULL));
@@ -3539,8 +3539,8 @@ dummy_func(
             DEOPT_IF(!Py_IS_TYPE(self, d_type));
             STAT_INC(CALL, hit);
             int nargs = total_args - 1;
-            _PyCFunctionFastWithKeywords cfunc =
-                (_PyCFunctionFastWithKeywords)(void(*)(void))meth->ml_meth;
+            PyCFunctionFastWithKeywords cfunc =
+                (PyCFunctionFastWithKeywords)(void(*)(void))meth->ml_meth;
             res = cfunc(self, args + 1, nargs, NULL);
             assert((res != NULL) ^ (_PyErr_Occurred(tstate) != NULL));
 
@@ -3597,8 +3597,8 @@ dummy_func(
             PyObject *self = args[0];
             DEOPT_IF(!Py_IS_TYPE(self, method->d_common.d_type));
             STAT_INC(CALL, hit);
-            _PyCFunctionFast cfunc =
-                (_PyCFunctionFast)(void(*)(void))meth->ml_meth;
+            PyCFunctionFast cfunc =
+                (PyCFunctionFast)(void(*)(void))meth->ml_meth;
             int nargs = total_args - 1;
             res = cfunc(self, args + 1, nargs);
             assert((res != NULL) ^ (_PyErr_Occurred(tstate) != NULL));