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Add METH_FASTCALL calling convention
Issue python#27810: Add a new calling convention for C functions: PyObject* func(PyObject *self, PyObject **args, Py_ssize_t nargs, PyObject *kwnames); Where args is a C array of positional arguments followed by values of keyword arguments. nargs is the number of positional arguments, kwnames are keys of keyword arguments. kwnames can be NULL.
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‎Include/abstract.h‎

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Original file line numberDiff line numberDiff line change
@@ -277,6 +277,22 @@ xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx*/
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PyObject *kwnames,
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PyObject *func);
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/* Convert (args, nargs, kwargs) into a (stack, nargs, kwnames).
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Return a new stack which should be released by PyMem_Free(), or return
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args unchanged if kwargs is NULL or an empty dictionary.
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The stack uses borrowed references.
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The type of keyword keys is not checked, these checks should be done
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later (ex: _PyArg_ParseStack). */
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PyAPI_FUNC(PyObject **) _PyStack_UnpackDict(
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PyObject **args,
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Py_ssize_t nargs,
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PyObject *kwargs,
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PyObject **kwnames,
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PyObject *func);
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/* Call the callable object func with the "fast call" calling convention:
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args is a C array for positional arguments (nargs is the number of
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positional arguments), kwargs is a dictionary for keyword arguments.

‎Include/methodobject.h‎

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@@ -16,6 +16,8 @@ PyAPI_DATA(PyTypeObject) PyCFunction_Type;
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#define PyCFunction_Check(op) (Py_TYPE(op) == &PyCFunction_Type)
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typedef PyObject *(*PyCFunction)(PyObject *, PyObject *);
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typedef PyObject *(*_PyCFunctionFast) (PyObject *self, PyObject **args,
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Py_ssize_t nargs, PyObject *kwnames);
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typedef PyObject *(*PyCFunctionWithKeywords)(PyObject *, PyObject *,
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PyObject *);
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typedef PyObject *(*PyNoArgsFunction)(PyObject *);
@@ -83,6 +85,8 @@ PyAPI_FUNC(PyObject *) PyCFunction_NewEx(PyMethodDef *, PyObject *,
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#define METH_COEXIST 0x0040
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#define METH_FASTCALL 0x0080
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#ifndef Py_LIMITED_API
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typedef struct {
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PyObject_HEAD

‎Objects/abstract.c‎

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Original file line numberDiff line numberDiff line change
@@ -2403,6 +2403,62 @@ _PyStack_AsDict(PyObject **values, Py_ssize_t nkwargs, PyObject *kwnames,
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return kwdict;
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}
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PyObject **
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_PyStack_UnpackDict(PyObject **args, Py_ssize_t nargs, PyObject *kwargs,
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PyObject **p_kwnames, PyObject *func)
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{
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PyObject **stack, **kwstack;
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Py_ssize_t nkwargs;
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Py_ssize_t pos, i;
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PyObject *key, *value;
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PyObject *kwnames;
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assert(nargs >= 0);
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assert(kwargs == NULL || PyDict_CheckExact(kwargs));
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nkwargs = (kwargs != NULL) ? PyDict_Size(kwargs) : 0;
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if (!nkwargs) {
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*p_kwnames = NULL;
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return args;
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}
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if ((size_t)nargs > PY_SSIZE_T_MAX / sizeof(stack[0]) - (size_t)nkwargs) {
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PyErr_NoMemory();
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return NULL;
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}
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stack = PyMem_Malloc((nargs + nkwargs) * sizeof(stack[0]));
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if (stack == NULL) {
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PyErr_NoMemory();
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return NULL;
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}
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kwnames = PyTuple_New(nkwargs);
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if (kwnames == NULL) {
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PyMem_Free(stack);
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return NULL;
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}
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/* Copy position arguments (borrowed references) */
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Py_MEMCPY(stack, args, nargs * sizeof(stack[0]));
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kwstack = stack + nargs;
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pos = i = 0;
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/* This loop doesn't support lookup function mutating the dictionary
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to change its size. It's a deliberate choice for speed, this function is
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called in the performance critical hot code. */
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while (PyDict_Next(kwargs, &pos, &key, &value)) {
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Py_INCREF(key);
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PyTuple_SET_ITEM(kwnames, i, key);
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/* The stack contains borrowed references */
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kwstack[i] = value;
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i++;
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}
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*p_kwnames = kwnames;
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return stack;
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}
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PyObject *
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_PyObject_FastCallKeywords(PyObject *func, PyObject **stack, Py_ssize_t nargs,
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PyObject *kwnames)

‎Objects/methodobject.c‎

Lines changed: 24 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -97,6 +97,11 @@ PyCFunction_Call(PyObject *func, PyObject *args, PyObject *kwds)
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if (flags == (METH_VARARGS | METH_KEYWORDS)) {
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res = (*(PyCFunctionWithKeywords)meth)(self, args, kwds);
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}
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else if (flags == METH_FASTCALL) {
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PyObject **stack = &PyTuple_GET_ITEM(args, 0);
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Py_ssize_t nargs = PyTuple_GET_SIZE(args);
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res = _PyCFunction_FastCallDict(func, stack, nargs, kwds);
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}
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else {
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if (kwds != NULL && PyDict_Size(kwds) != 0) {
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PyErr_Format(PyExc_TypeError, "%.200s() takes no keyword arguments",
@@ -232,6 +237,25 @@ _PyCFunction_FastCallDict(PyObject *func_obj, PyObject **args, Py_ssize_t nargs,
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break;
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}
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case METH_FASTCALL:
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{
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PyObject **stack;
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PyObject *kwnames;
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_PyCFunctionFast fastmeth = (_PyCFunctionFast)meth;
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stack = _PyStack_UnpackDict(args, nargs, kwargs, &kwnames, func_obj);
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if (stack == NULL) {
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return NULL;
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}
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result = (*fastmeth) (self, stack, nargs, kwnames);
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if (stack != args) {
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PyMem_Free(stack);
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}
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Py_XDECREF(kwnames);
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break;
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}
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default:
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PyErr_SetString(PyExc_SystemError,
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"Bad call flags in PyCFunction_Call. "

‎Python/getargs.c‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1992,8 +1992,9 @@ vgetargskeywordsfast(PyObject *args, PyObject *keywords,
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return cleanreturn(0, &freelist);
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}
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}
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else if (i < nargs)
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else if (i < nargs) {
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current_arg = PyTuple_GET_ITEM(args, i);
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}
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if (current_arg) {
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msg = convertitem(current_arg, &format, p_va, flags,

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