bpo-20201: variadic arguments support for AC (GH-18609)

Implement support for `*args` in AC, and port `print()` to use it.

Include/modsupport.h

@@ -50,6 +50,7 @@ PyAPI_FUNC(PyObject *) Py_BuildValue(const char *, ...);
 PyAPI_FUNC(PyObject *) _Py_BuildValue_SizeT(const char *, ...);
 
 
+#define ANY_VARARGS(n) (n == PY_SSIZE_T_MAX)
 #ifndef Py_LIMITED_API
 PyAPI_FUNC(int) _PyArg_UnpackStack(
     PyObject *const *args,
@@ -73,7 +74,7 @@ PyAPI_FUNC(void) _PyArg_BadArgument(const char *, const char *, const char *, Py
 PyAPI_FUNC(int) _PyArg_CheckPositional(const char *, Py_ssize_t,
                                        Py_ssize_t, Py_ssize_t);
 #define _PyArg_CheckPositional(funcname, nargs, min, max) \
-    (((min) <= (nargs) && (nargs) <= (max)) \
+    ((!ANY_VARARGS(max) && (min) <= (nargs) && (nargs) <= (max)) \
      || _PyArg_CheckPositional((funcname), (nargs), (min), (max)))
 
 #endif
@@ -127,6 +128,14 @@ PyAPI_FUNC(PyObject * const *) _PyArg_UnpackKeywords(
         struct _PyArg_Parser *parser,
         int minpos, int maxpos, int minkw,
         PyObject **buf);
+
+PyAPI_FUNC(PyObject * const *) _PyArg_UnpackKeywordsWithVararg(
+        PyObject *const *args, Py_ssize_t nargs,
+        PyObject *kwargs, PyObject *kwnames,
+        struct _PyArg_Parser *parser,
+        int minpos, int maxpos, int minkw,
+        int vararg, PyObject **buf);
+
 #define _PyArg_UnpackKeywords(args, nargs, kwargs, kwnames, parser, minpos, maxpos, minkw, buf) \
     (((minkw) == 0 && (kwargs) == NULL && (kwnames) == NULL && \
       (minpos) <= (nargs) && (nargs) <= (maxpos) && args != NULL) ? (args) : \

Lib/test/clinic.test

@@ -3304,3 +3304,223 @@ test_preprocessor_guarded_else(PyObject *module, PyObject *Py_UNUSED(ignored))
     #define TEST_PREPROCESSOR_GUARDED_ELSE_METHODDEF
 #endif /* !defined(TEST_PREPROCESSOR_GUARDED_ELSE_METHODDEF) */
 /*[clinic end generated code: output=3804bb18d454038c input=3fc80c9989d2f2e1]*/
+
+/*[clinic input]
+test_vararg_and_posonly
+
+
+    a: object
+    *args: object
+    /
+
+[clinic start generated code]*/
+
+PyDoc_STRVAR(test_vararg_and_posonly__doc__,
+"test_vararg_and_posonly($module, a, /, *args)\n"
+"--\n"
+"\n");
+
+#define TEST_VARARG_AND_POSONLY_METHODDEF    \
+    {"test_vararg_and_posonly", (PyCFunction)(void(*)(void))test_vararg_and_posonly, METH_FASTCALL, test_vararg_and_posonly__doc__},
+
+static PyObject *
+test_vararg_and_posonly_impl(PyObject *module, PyObject *a, PyObject *args);
+
+static PyObject *
+test_vararg_and_posonly(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+{
+    PyObject *return_value = NULL;
+    PyObject *a;
+    PyObject *__clinic_args = NULL;
+
+    if (!_PyArg_CheckPositional("test_vararg_and_posonly", nargs, 1, PY_SSIZE_T_MAX)) {
+        goto exit;
+    }
+    a = args[0];
+    __clinic_args = PyTuple_New(nargs - 1);
+    for (Py_ssize_t i = 0; i < nargs - 1; ++i) {
+        PyTuple_SET_ITEM(__clinic_args, i, args[1 + i]);
+    }
+    return_value = test_vararg_and_posonly_impl(module, a, __clinic_args);
+
+exit:
+    Py_XDECREF(__clinic_args);
+    return return_value;
+}
+
+static PyObject *
+test_vararg_and_posonly_impl(PyObject *module, PyObject *a, PyObject *args)
+/*[clinic end generated code: output=ada613d2d87c9341 input=08dc2bf7afbf1613]*/
+
+/*[clinic input]
+test_vararg
+
+
+    a: object
+    *args: object
+
+[clinic start generated code]*/
+
+PyDoc_STRVAR(test_vararg__doc__,
+"test_vararg($module, /, a, *args)\n"
+"--\n"
+"\n");
+
+#define TEST_VARARG_METHODDEF    \
+    {"test_vararg", (PyCFunction)(void(*)(void))test_vararg, METH_FASTCALL|METH_KEYWORDS, test_vararg__doc__},
+
+static PyObject *
+test_vararg_impl(PyObject *module, PyObject *a, PyObject *args);
+
+static PyObject *
+test_vararg(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"a", NULL};
+    static _PyArg_Parser _parser = {NULL, _keywords, "test_vararg", 0};
+    PyObject *argsbuf[2];
+    Py_ssize_t noptargs = 0 + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 1;
+    PyObject *a;
+    PyObject *__clinic_args = NULL;
+
+    args = _PyArg_UnpackKeywordsWithVararg(args, nargs, NULL, kwnames, &_parser, 1, 1, 0, 1, argsbuf);
+    if (!args) {
+        goto exit;
+    }
+    a = args[0];
+    __clinic_args = args[1];
+    return_value = test_vararg_impl(module, a, __clinic_args);
+
+exit:
+    Py_XDECREF(__clinic_args);
+    return return_value;
+}
+
+static PyObject *
+test_vararg_impl(PyObject *module, PyObject *a, PyObject *args)
+/*[clinic end generated code: output=f721025731c3bfe8 input=81d33815ad1bae6e]*/
+
+/*[clinic input]
+test_vararg_with_default
+
+
+    a: object
+    *args: object
+    b: bool = False
+
+[clinic start generated code]*/
+
+PyDoc_STRVAR(test_vararg_with_default__doc__,
+"test_vararg_with_default($module, /, a, *args, b=False)\n"
+"--\n"
+"\n");
+
+#define TEST_VARARG_WITH_DEFAULT_METHODDEF    \
+    {"test_vararg_with_default", (PyCFunction)(void(*)(void))test_vararg_with_default, METH_FASTCALL|METH_KEYWORDS, test_vararg_with_default__doc__},
+
+static PyObject *
+test_vararg_with_default_impl(PyObject *module, PyObject *a, PyObject *args,
+                              int b);
+
+static PyObject *
+test_vararg_with_default(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"a", "b", NULL};
+    static _PyArg_Parser _parser = {NULL, _keywords, "test_vararg_with_default", 0};
+    PyObject *argsbuf[3];
+    Py_ssize_t noptargs = 0 + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 1;
+    PyObject *a;
+    PyObject *__clinic_args = NULL;
+    int b = 0;
+
+    args = _PyArg_UnpackKeywordsWithVararg(args, nargs, NULL, kwnames, &_parser, 1, 1, 0, 1, argsbuf);
+    if (!args) {
+        goto exit;
+    }
+    a = args[0];
+    __clinic_args = args[1];
+    if (!noptargs) {
+        goto skip_optional_kwonly;
+    }
+    b = PyObject_IsTrue(args[2]);
+    if (b < 0) {
+        goto exit;
+    }
+skip_optional_kwonly:
+    return_value = test_vararg_with_default_impl(module, a, __clinic_args, b);
+
+exit:
+    Py_XDECREF(__clinic_args);
+    return return_value;
+}
+
+static PyObject *
+test_vararg_with_default_impl(PyObject *module, PyObject *a, PyObject *args,
+                              int b)
+/*[clinic end generated code: output=63b34d3241c52fda input=6e110b54acd9b22d]*/
+
+/*[clinic input]
+test_vararg_with_only_defaults
+
+
+    *args: object
+    b: bool = False
+    c: object = ' '
+
+[clinic start generated code]*/
+
+PyDoc_STRVAR(test_vararg_with_only_defaults__doc__,
+"test_vararg_with_only_defaults($module, /, *args, b=False, c=\' \')\n"
+"--\n"
+"\n");
+
+#define TEST_VARARG_WITH_ONLY_DEFAULTS_METHODDEF    \
+    {"test_vararg_with_only_defaults", (PyCFunction)(void(*)(void))test_vararg_with_only_defaults, METH_FASTCALL|METH_KEYWORDS, test_vararg_with_only_defaults__doc__},
+
+static PyObject *
+test_vararg_with_only_defaults_impl(PyObject *module, PyObject *args, int b,
+                                    PyObject *c);
+
+static PyObject *
+test_vararg_with_only_defaults(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"b", "c", NULL};
+    static _PyArg_Parser _parser = {NULL, _keywords, "test_vararg_with_only_defaults", 0};
+    PyObject *argsbuf[3];
+    Py_ssize_t noptargs = 0 + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 0;
+    PyObject *__clinic_args = NULL;
+    int b = 0;
+    PyObject *c = " ";
+
+    args = _PyArg_UnpackKeywordsWithVararg(args, nargs, NULL, kwnames, &_parser, 0, 0, 0, 0, argsbuf);
+    if (!args) {
+        goto exit;
+    }
+    __clinic_args = args[0];
+    if (!noptargs) {
+        goto skip_optional_kwonly;
+    }
+    if (args[1]) {
+        b = PyObject_IsTrue(args[1]);
+        if (b < 0) {
+            goto exit;
+        }
+        if (!--noptargs) {
+            goto skip_optional_kwonly;
+        }
+    }
+    c = args[2];
+skip_optional_kwonly:
+    return_value = test_vararg_with_only_defaults_impl(module, __clinic_args, b, c);
+
+exit:
+    Py_XDECREF(__clinic_args);
+    return return_value;
+}
+
+static PyObject *
+test_vararg_with_only_defaults_impl(PyObject *module, PyObject *args, int b,
+                                    PyObject *c)
+/*[clinic end generated code: output=dc29ce6ebc2ec10c input=fa56a709a035666e]*/

Lib/test/test_call.py

@@ -129,7 +129,7 @@ class CFunctionCallsErrorMessages(unittest.TestCase):
                                min, 0, default=1, key=2, foo=3)
 
     def test_varargs17_kw(self):
-        msg = r"^print\(\) takes at most 4 keyword arguments \(5 given\)$"
+        msg = r"'foo' is an invalid keyword argument for print\(\)$"
         self.assertRaisesRegex(TypeError, msg,
                                print, 0, sep=1, end=2, file=3, flush=4, foo=5)
 

Misc/NEWS.d/next/Tools-Demos/2020-02-25-18-22-09.bpo-20291.AyrDiZ.rst

@@ -0,0 +1 @@
+Added support for variadic positional parameters in Argument Clinic.

Python/bltinmodule.c

@@ -1952,24 +1952,31 @@ builtin_pow_impl(PyObject *module, PyObject *base, PyObject *exp,
     return PyNumber_Power(base, exp, mod);
 }
 
+/*[clinic input]
+print as builtin_print
+
+    *args: object
+    sep: object(c_default="Py_None") = ' '
+        string inserted between values, default a space.
+    end: object(c_default="Py_None") = '\n'
+        string appended after the last value, default a newline.
+    file: object = None
+        a file-like object (stream); defaults to the current sys.stdout.
+    flush: bool = False
+        whether to forcibly flush the stream.
+
+Prints the values to a stream, or to sys.stdout by default.
+
+[clinic start generated code]*/
 
-/* AC: cannot convert yet, waiting for *args support */
 static PyObject *
-builtin_print(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+builtin_print_impl(PyObject *module, PyObject *args, PyObject *sep,
+                   PyObject *end, PyObject *file, int flush)
+/*[clinic end generated code: output=3cfc0940f5bc237b input=c143c575d24fe665]*/
 {
-    static const char * const _keywords[] = {"sep", "end", "file", "flush", 0};
-    static struct _PyArg_Parser _parser = {"|OOOp:print", _keywords, 0};
-    PyObject *sep = NULL, *end = NULL, *file = NULL;
-    int flush = 0;
     int i, err;
 
-    if (kwnames != NULL &&
-            !_PyArg_ParseStackAndKeywords(args + nargs, 0, kwnames, &_parser,
-                                          &sep, &end, &file, &flush)) {
-        return NULL;
-    }
-
-    if (file == NULL || file == Py_None) {
+    if (file == Py_None) {
         file = _PySys_GetObjectId(&PyId_stdout);
         if (file == NULL) {
             PyErr_SetString(PyExc_RuntimeError, "lost sys.stdout");
@@ -1977,8 +1984,9 @@ builtin_print(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyObject
         }
 
         /* sys.stdout may be None when FILE* stdout isn't connected */
-        if (file == Py_None)
+        if (file == Py_None) {
             Py_RETURN_NONE;
+        }
     }
 
     if (sep == Py_None) {
@@ -2000,48 +2008,45 @@ builtin_print(PyObject *self, PyObject *const *args, Py_ssize_t nargs, PyObject
         return NULL;
     }
 
-    for (i = 0; i < nargs; i++) {
+    for (i = 0; i < PyTuple_GET_SIZE(args); i++) {
         if (i > 0) {
-            if (sep == NULL)
+            if (sep == NULL) {
                 err = PyFile_WriteString(" ", file);
-            else
-                err = PyFile_WriteObject(sep, file,
-                                         Py_PRINT_RAW);
-            if (err)
+            }
+            else {
+                err = PyFile_WriteObject(sep, file, Py_PRINT_RAW);
+            }
+            if (err) {
                 return NULL;
+            }
         }
-        err = PyFile_WriteObject(args[i], file, Py_PRINT_RAW);
-        if (err)
+        err = PyFile_WriteObject(PyTuple_GET_ITEM(args, i), file, Py_PRINT_RAW);
+        if (err) {
             return NULL;
+        }
     }
 
-    if (end == NULL)
+    if (end == NULL) {
         err = PyFile_WriteString("\n", file);
-    else
+    }
+    else {
         err = PyFile_WriteObject(end, file, Py_PRINT_RAW);
-    if (err)
+    }
+    if (err) {
         return NULL;
+    }
 
     if (flush) {
         PyObject *tmp = _PyObject_CallMethodIdNoArgs(file, &PyId_flush);
-        if (tmp == NULL)
+        if (tmp == NULL) {
             return NULL;
+        }
         Py_DECREF(tmp);
     }
 
     Py_RETURN_NONE;
 }
 
-PyDoc_STRVAR(print_doc,
-"print(value, ..., sep=' ', end='\\n', file=sys.stdout, flush=False)\n\
-\n\
-Prints the values to a stream, or to sys.stdout by default.\n\
-Optional keyword arguments:\n\
-file:  a file-like object (stream); defaults to the current sys.stdout.\n\
-sep:   string inserted between values, default a space.\n\
-end:   string appended after the last value, default a newline.\n\
-flush: whether to forcibly flush the stream.");
-
 
 /*[clinic input]
 input as builtin_input
@@ -2644,7 +2649,6 @@ builtin_issubclass_impl(PyObject *module, PyObject *cls,
     return PyBool_FromLong(retval);
 }
 
-
 typedef struct {
     PyObject_HEAD
     Py_ssize_t tuplesize;
@@ -2955,7 +2959,7 @@ static PyMethodDef builtin_methods[] = {
     BUILTIN_OCT_METHODDEF
     BUILTIN_ORD_METHODDEF
     BUILTIN_POW_METHODDEF
-    {"print",           (PyCFunction)(void(*)(void))builtin_print,      METH_FASTCALL | METH_KEYWORDS, print_doc},
+    BUILTIN_PRINT_METHODDEF
     BUILTIN_REPR_METHODDEF
     BUILTIN_ROUND_METHODDEF
     BUILTIN_SETATTR_METHODDEF

Python/clinic/bltinmodule.c.h

@@ -674,6 +674,80 @@ exit:
     return return_value;
 }
 
+PyDoc_STRVAR(builtin_print__doc__,
+"print($module, /, *args, sep=\' \', end=\'\\n\', file=None, flush=False)\n"
+"--\n"
+"\n"
+"Prints the values to a stream, or to sys.stdout by default.\n"
+"\n"
+"  sep\n"
+"    string inserted between values, default a space.\n"
+"  end\n"
+"    string appended after the last value, default a newline.\n"
+"  file\n"
+"    a file-like object (stream); defaults to the current sys.stdout.\n"
+"  flush\n"
+"    whether to forcibly flush the stream.");
+
+#define BUILTIN_PRINT_METHODDEF    \
+    {"print", (PyCFunction)(void(*)(void))builtin_print, METH_FASTCALL|METH_KEYWORDS, builtin_print__doc__},
+
+static PyObject *
+builtin_print_impl(PyObject *module, PyObject *args, PyObject *sep,
+                   PyObject *end, PyObject *file, int flush);
+
+static PyObject *
+builtin_print(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"sep", "end", "file", "flush", NULL};
+    static _PyArg_Parser _parser = {NULL, _keywords, "print", 0};
+    PyObject *argsbuf[5];
+    Py_ssize_t noptargs = 0 + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 0;
+    PyObject *__clinic_args = NULL;
+    PyObject *sep = Py_None;
+    PyObject *end = Py_None;
+    PyObject *file = Py_None;
+    int flush = 0;
+
+    args = _PyArg_UnpackKeywordsWithVararg(args, nargs, NULL, kwnames, &_parser, 0, 0, 0, 0, argsbuf);
+    if (!args) {
+        goto exit;
+    }
+    __clinic_args = args[0];
+    if (!noptargs) {
+        goto skip_optional_kwonly;
+    }
+    if (args[1]) {
+        sep = args[1];
+        if (!--noptargs) {
+            goto skip_optional_kwonly;
+        }
+    }
+    if (args[2]) {
+        end = args[2];
+        if (!--noptargs) {
+            goto skip_optional_kwonly;
+        }
+    }
+    if (args[3]) {
+        file = args[3];
+        if (!--noptargs) {
+            goto skip_optional_kwonly;
+        }
+    }
+    flush = PyObject_IsTrue(args[4]);
+    if (flush < 0) {
+        goto exit;
+    }
+skip_optional_kwonly:
+    return_value = builtin_print_impl(module, __clinic_args, sep, end, file, flush);
+
+exit:
+    Py_XDECREF(__clinic_args);
+    return return_value;
+}
+
 PyDoc_STRVAR(builtin_input__doc__,
 "input($module, prompt=None, /)\n"
 "--\n"
@@ -877,4 +951,4 @@ builtin_issubclass(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=e1d8057298b5de61 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=77ace832b3fb38e0 input=a9049054013a1b77]*/

Python/getargs.c

@@ -2465,6 +2465,166 @@ _PyArg_UnpackKeywords(PyObject *const *args, Py_ssize_t nargs,
     return buf;
 }
 
+PyObject * const *
+_PyArg_UnpackKeywordsWithVararg(PyObject *const *args, Py_ssize_t nargs,
+                                PyObject *kwargs, PyObject *kwnames,
+                                struct _PyArg_Parser *parser,
+                                int minpos, int maxpos, int minkw,
+                                int vararg, PyObject **buf)
+{
+    PyObject *kwtuple;
+    PyObject *keyword;
+    Py_ssize_t varargssize = 0;
+    int i, posonly, minposonly, maxargs;
+    int reqlimit = minkw ? maxpos + minkw : minpos;
+    Py_ssize_t nkwargs;
+    PyObject *current_arg;
+    PyObject * const *kwstack = NULL;
+
+    assert(kwargs == NULL || PyDict_Check(kwargs));
+    assert(kwargs == NULL || kwnames == NULL);
+
+    if (parser == NULL) {
+        PyErr_BadInternalCall();
+        return NULL;
+    }
+
+    if (kwnames != NULL && !PyTuple_Check(kwnames)) {
+        PyErr_BadInternalCall();
+        return NULL;
+    }
+
+    if (args == NULL && nargs == 0) {
+        args = buf;
+    }
+
+    if (!parser_init(parser)) {
+        return NULL;
+    }
+
+    kwtuple = parser->kwtuple;
+    posonly = parser->pos;
+    minposonly = Py_MIN(posonly, minpos);
+    maxargs = posonly + (int)PyTuple_GET_SIZE(kwtuple);
+    if (kwargs != NULL) {
+        nkwargs = PyDict_GET_SIZE(kwargs);
+    }
+    else if (kwnames != NULL) {
+        nkwargs = PyTuple_GET_SIZE(kwnames);
+        kwstack = args + nargs;
+    }
+    else {
+        nkwargs = 0;
+    }
+    if (nargs < minposonly) {
+        PyErr_Format(PyExc_TypeError,
+                     "%.200s%s takes %s %d positional argument%s"
+                     " (%zd given)",
+                     (parser->fname == NULL) ? "function" : parser->fname,
+                     (parser->fname == NULL) ? "" : "()",
+                     minposonly < maxpos ? "at least" : "exactly",
+                     minposonly,
+                     minposonly == 1 ? "" : "s",
+                     nargs);
+        return NULL;
+    }
+
+    /* create varargs tuple */
+    varargssize = nargs - maxpos;
+    if (varargssize < 0) {
+        varargssize = 0;
+    }
+    buf[vararg] = PyTuple_New(varargssize);
+    if (!buf[vararg]) {
+        return NULL;
+    }
+
+    /* copy tuple args */
+    for (i = 0; i < nargs; i++) {
+        if (i >= vararg) {
+            Py_INCREF(args[i]);
+            PyTuple_SET_ITEM(buf[vararg], i - vararg, args[i]);
+            continue;
+        }
+        else {
+            buf[i] = args[i];
+        }
+    }
+
+    /* copy keyword args using kwtuple to drive process */
+    for (i = Py_MAX((int)nargs, posonly) - varargssize; i < maxargs; i++) {
+        if (nkwargs) {
+            keyword = PyTuple_GET_ITEM(kwtuple, i - posonly);
+            if (kwargs != NULL) {
+                current_arg = PyDict_GetItemWithError(kwargs, keyword);
+                if (!current_arg && PyErr_Occurred()) {
+                    goto exit;
+                }
+            }
+            else {
+                current_arg = find_keyword(kwnames, kwstack, keyword);
+            }
+        }
+        else {
+            current_arg = NULL;
+        }
+
+        buf[i + vararg + 1] = current_arg;
+
+        if (current_arg) {
+            --nkwargs;
+        }
+        else if (i < minpos || (maxpos <= i && i < reqlimit)) {
+            /* Less arguments than required */
+            keyword = PyTuple_GET_ITEM(kwtuple, i - posonly);
+            PyErr_Format(PyExc_TypeError,  "%.200s%s missing required "
+                         "argument '%U' (pos %d)",
+                         (parser->fname == NULL) ? "function" : parser->fname,
+                         (parser->fname == NULL) ? "" : "()",
+                         keyword, i+1);
+            goto exit;
+        }
+    }
+
+    if (nkwargs > 0) {
+        Py_ssize_t j;
+        /* make sure there are no extraneous keyword arguments */
+        j = 0;
+        while (1) {
+            int match;
+            if (kwargs != NULL) {
+                if (!PyDict_Next(kwargs, &j, &keyword, NULL))
+                    break;
+            }
+            else {
+                if (j >= PyTuple_GET_SIZE(kwnames))
+                    break;
+                keyword = PyTuple_GET_ITEM(kwnames, j);
+                j++;
+            }
+
+            match = PySequence_Contains(kwtuple, keyword);
+            if (match <= 0) {
+                if (!match) {
+                    PyErr_Format(PyExc_TypeError,
+                                 "'%S' is an invalid keyword "
+                                 "argument for %.200s%s",
+                                 keyword,
+                                 (parser->fname == NULL) ? "this function" : parser->fname,
+                                 (parser->fname == NULL) ? "" : "()");
+                }
+                goto exit;
+            }
+        }
+    }
+
+    return buf;
+
+exit:
+    Py_XDECREF(buf[vararg]);
+    return NULL;
+}
+
 
 static const char *
 skipitem(const char **p_format, va_list *p_va, int flags)

Tools/clinic/clinic.py

@@ -44,6 +44,9 @@ NoneType = type(None)
 version = '1'
 
 NoneType = type(None)
+NO_VARARG = "PY_SSIZE_T_MAX"
+CLINIC_PREFIX = "__clinic_"
+CLINIC_PREFIXED_ARGS = {"args"}
 
 class Unspecified:
     def __repr__(self):
@@ -644,14 +647,21 @@ class CLanguage(Language):
 
         new_or_init = f.kind in (METHOD_NEW, METHOD_INIT)
 
-        pos_only = min_pos = max_pos = min_kw_only = 0
+        vararg = NO_VARARG
+        pos_only = min_pos = max_pos = min_kw_only = pseudo_args = 0
         for i, p in enumerate(parameters, 1):
-            if p.is_keyword_only():
+            if p.is_keyword_only() or vararg != NO_VARARG:
                 assert not p.is_positional_only()
                 if not p.is_optional():
                     min_kw_only = i - max_pos
+            elif p.is_vararg():
+                if vararg != NO_VARARG:
+                    fail("Too many var args")
+                pseudo_args += 1
+                vararg = i - 1
             else:
-                max_pos = i
+                if vararg == NO_VARARG:
+                    max_pos = i
                 if p.is_positional_only():
                     pos_only = i
                 if not p.is_optional():
@@ -834,7 +844,7 @@ class CLanguage(Language):
 
             parser_definition = parser_body(parser_prototype, '    {option_group_parsing}')
 
-        elif not requires_defining_class and pos_only == len(parameters):
+        elif not requires_defining_class and pos_only == len(parameters) - pseudo_args:
             if not new_or_init:
                 # positional-only, but no option groups
                 # we only need one call to _PyArg_ParseStack
@@ -852,15 +862,44 @@ class CLanguage(Language):
                 nargs = 'PyTuple_GET_SIZE(args)'
                 argname_fmt = 'PyTuple_GET_ITEM(args, %d)'
 
+
+            left_args = "{} - {}".format(nargs, max_pos)
+            max_args = NO_VARARG if (vararg != NO_VARARG) else max_pos
             parser_code = [normalize_snippet("""
-                if (!_PyArg_CheckPositional("{name}", %s, %d, %d)) {{
+                if (!_PyArg_CheckPositional("{name}", %s, %d, %s)) {{
                     goto exit;
                 }}
-                """ % (nargs, min_pos, max_pos), indent=4)]
+                """ % (nargs, min_pos, max_args), indent=4)]
+
             has_optional = False
             for i, p in enumerate(parameters):
                 displayname = p.get_displayname(i+1)
-                parsearg = p.converter.parse_arg(argname_fmt % i, displayname)
+                argname = argname_fmt % i
+
+                if p.is_vararg():
+                    if not new_or_init:
+                        parser_code.append(normalize_snippet("""
+                            %s = PyTuple_New(%s);
+                            for (Py_ssize_t i = 0; i < %s; ++i) {{
+                                PyTuple_SET_ITEM(%s, i, args[%d + i]);
+                            }}
+                            """ % (
+                                p.converter.parser_name,
+                                left_args,
+                                left_args,
+                                p.converter.parser_name,
+                                max_pos
+                            ), indent=4))
+                    else:
+                        parser_code.append(normalize_snippet("""
+                            %s = PyTuple_GetSlice(%d, -1);
+                            """ % (
+                                p.converter.parser_name,
+                                max_pos
+                            ), indent=4))
+                    continue
+
+                parsearg = p.converter.parse_arg(argname, displayname)
                 if parsearg is None:
                     #print('Cannot convert %s %r for %s' % (p.converter.__class__.__name__, p.converter.format_unit, p.converter.name), file=sys.stderr)
                     parser_code = None
@@ -896,6 +935,19 @@ class CLanguage(Language):
 
         else:
             has_optional_kw = (max(pos_only, min_pos) + min_kw_only < len(converters))
+            if vararg == NO_VARARG:
+                args_declaration = "_PyArg_UnpackKeywords", "%s, %s, %s" % (
+                    min_pos,
+                    max_pos,
+                    min_kw_only
+                )
+            else:
+                args_declaration = "_PyArg_UnpackKeywordsWithVararg", "%s, %s, %s, %s" % (
+                    min_pos,
+                    max_pos,
+                    min_kw_only,
+                    vararg
+                )
             if not new_or_init:
                 flags = "METH_FASTCALL|METH_KEYWORDS"
                 parser_prototype = parser_prototype_fastcall_keywords
@@ -906,13 +958,14 @@ class CLanguage(Language):
                     PyObject *argsbuf[%s];
                     """ % len(converters))
                 if has_optional_kw:
-                    declarations += "\nPy_ssize_t noptargs = nargs + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - %d;" % (min_pos + min_kw_only)
+                    pre_buffer = "0" if vararg != NO_VARARG else "nargs"
+                    declarations += "\nPy_ssize_t noptargs = %s + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - %d;" % (pre_buffer, min_pos + min_kw_only)
                 parser_code = [normalize_snippet("""
-                    args = _PyArg_UnpackKeywords(args, nargs, NULL, kwnames, &_parser, %d, %d, %d, argsbuf);
+                    args = %s(args, nargs, NULL, kwnames, &_parser, %s, argsbuf);
                     if (!args) {{
                         goto exit;
                     }}
-                    """ % (min_pos, max_pos, min_kw_only), indent=4)]
+                    """ % args_declaration, indent=4)]
             else:
                 # positional-or-keyword arguments
                 flags = "METH_VARARGS|METH_KEYWORDS"
@@ -928,11 +981,12 @@ class CLanguage(Language):
                 if has_optional_kw:
                     declarations += "\nPy_ssize_t noptargs = nargs + (kwargs ? PyDict_GET_SIZE(kwargs) : 0) - %d;" % (min_pos + min_kw_only)
                 parser_code = [normalize_snippet("""
-                    fastargs = _PyArg_UnpackKeywords(_PyTuple_CAST(args)->ob_item, nargs, kwargs, NULL, &_parser, %d, %d, %d, argsbuf);
+                    fastargs = %s(_PyTuple_CAST(args)->ob_item, nargs, kwargs, NULL, &_parser, %s, argsbuf);
                     if (!fastargs) {{
                         goto exit;
                     }}
-                    """ % (min_pos, max_pos, min_kw_only), indent=4)]
+                    """ % args_declaration, indent=4)]
+
             if requires_defining_class:
                 flags = 'METH_METHOD|' + flags
                 parser_prototype = parser_prototype_def_class
@@ -969,6 +1023,8 @@ class CLanguage(Language):
                     else:
                         label = 'skip_optional_kwonly'
                         first_opt = max_pos + min_kw_only
+                        if vararg != NO_VARARG:
+                            first_opt += 1
                     if i == first_opt:
                         add_label = label
                         parser_code.append(normalize_snippet("""
@@ -1249,6 +1305,9 @@ class CLanguage(Language):
             if (i != -1) and (p.default is not unspecified):
                 first_optional = min(first_optional, i)
 
+            if p.is_vararg():
+                data.cleanup.append("Py_XDECREF({});".format(c.parser_name))
+
             # insert group variable
             group = p.group
             if last_group != group:
@@ -2307,8 +2366,11 @@ class Parameter:
     def is_positional_only(self):
         return self.kind == inspect.Parameter.POSITIONAL_ONLY
 
+    def is_vararg(self):
+        return self.kind == inspect.Parameter.VAR_POSITIONAL
+
     def is_optional(self):
-        return (self.default is not unspecified)
+        return not self.is_vararg() and (self.default is not unspecified)
 
     def copy(self, **overrides):
         kwargs = {
@@ -2523,7 +2585,7 @@ class CConverter(metaclass=CConverterAutoRegister):
 
     def _render_self(self, parameter, data):
         self.parameter = parameter
-        name = self.name
+        name = self.parser_name
 
         # impl_arguments
         s = ("&" if self.impl_by_reference else "") + name
@@ -2541,7 +2603,7 @@ class CConverter(metaclass=CConverterAutoRegister):
         name = self.name
 
         # declarations
-        d = self.declaration()
+        d = self.declaration(in_parser=True)
         data.declarations.append(d)
 
         # initializers
@@ -2555,7 +2617,9 @@ class CConverter(metaclass=CConverterAutoRegister):
             data.modifications.append('/* modifications for ' + name + ' */\n' + modifications.rstrip())
 
         # keywords
-        if parameter.is_positional_only():
+        if parameter.is_vararg():
+            pass
+        elif parameter.is_positional_only():
             data.keywords.append('')
         else:
             data.keywords.append(parameter.name)
@@ -2587,7 +2651,7 @@ class CConverter(metaclass=CConverterAutoRegister):
         """Computes the name of the associated "length" variable."""
         if not self.length:
             return None
-        return self.name + "_length"
+        return self.parser_name + "_length"
 
     # Why is this one broken out separately?
     # For "positional-only" function parsing,
@@ -2613,7 +2677,7 @@ class CConverter(metaclass=CConverterAutoRegister):
     # All the functions after here are intended as extension points.
     #
 
-    def simple_declaration(self, by_reference=False):
+    def simple_declaration(self, by_reference=False, *, in_parser=False):
         """
         Computes the basic declaration of the variable.
         Used in computing the prototype declaration and the
@@ -2624,14 +2688,18 @@ class CConverter(metaclass=CConverterAutoRegister):
             prototype.append(" ")
         if by_reference:
             prototype.append('*')
-        prototype.append(self.name)
+        if in_parser:
+            name = self.parser_name
+        else:
+            name = self.name
+        prototype.append(name)
         return "".join(prototype)
 
-    def declaration(self):
+    def declaration(self, *, in_parser=False):
         """
         The C statement to declare this variable.
         """
-        declaration = [self.simple_declaration()]
+        declaration = [self.simple_declaration(in_parser=True)]
         default = self.c_default
         if not default and self.parameter.group:
             default = self.c_ignored_default
@@ -2683,7 +2751,7 @@ class CConverter(metaclass=CConverterAutoRegister):
                 if (!{converter}({argname}, &{paramname})) {{{{
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            converter=self.converter)
         if self.format_unit == 'O!':
             cast = '(%s)' % self.type if self.type != 'PyObject *' else ''
@@ -2695,7 +2763,7 @@ class CConverter(metaclass=CConverterAutoRegister):
                         goto exit;
                     }}}}
                     {paramname} = {cast}{argname};
-                    """.format(argname=argname, paramname=self.name,
+                    """.format(argname=argname, paramname=self.parser_name,
                                displayname=displayname, typecheck=typecheck,
                                typename=typename, cast=cast)
             return """
@@ -2704,19 +2772,25 @@ class CConverter(metaclass=CConverterAutoRegister):
                     goto exit;
                 }}}}
                 {paramname} = {cast}{argname};
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            subclass_of=self.subclass_of, cast=cast,
                            displayname=displayname)
         if self.format_unit == 'O':
             cast = '(%s)' % self.type if self.type != 'PyObject *' else ''
             return """
                 {paramname} = {cast}{argname};
-                """.format(argname=argname, paramname=self.name, cast=cast)
+                """.format(argname=argname, paramname=self.parser_name, cast=cast)
         return None
 
     def set_template_dict(self, template_dict):
         pass
 
+    @property
+    def parser_name(self):
+        if self.name in CLINIC_PREFIXED_ARGS: # bpo-39741
+            return CLINIC_PREFIX + self.name
+        else:
+            return self.name
 
 type_checks = {
     '&PyLong_Type': ('PyLong_Check', 'int'),
@@ -2755,14 +2829,14 @@ class bool_converter(CConverter):
                 if ({paramname} == -1 && PyErr_Occurred()) {{{{
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         elif self.format_unit == 'p':
             return """
                 {paramname} = PyObject_IsTrue({argname});
                 if ({paramname} < 0) {{{{
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 class defining_class_converter(CConverter):
@@ -2812,7 +2886,7 @@ class char_converter(CConverter):
                     _PyArg_BadArgument("{{name}}", {displayname}, "a byte string of length 1", {argname});
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            displayname=displayname)
         return super().parse_arg(argname, displayname)
 
@@ -2850,7 +2924,7 @@ class unsigned_char_converter(CConverter):
                         {paramname} = (unsigned char) ival;
                     }}}}
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         elif self.format_unit == 'B':
             return """
                 {{{{
@@ -2862,7 +2936,7 @@ class unsigned_char_converter(CConverter):
                         {paramname} = (unsigned char) ival;
                     }}}}
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 class byte_converter(unsigned_char_converter): pass
@@ -2895,7 +2969,7 @@ class short_converter(CConverter):
                         {paramname} = (short) ival;
                     }}}}
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 class unsigned_short_converter(CConverter):
@@ -2916,7 +2990,7 @@ class unsigned_short_converter(CConverter):
                 if ({paramname} == (unsigned short)-1 && PyErr_Occurred()) {{{{
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 @add_legacy_c_converter('C', accept={str})
@@ -2941,7 +3015,7 @@ class int_converter(CConverter):
                 if ({paramname} == -1 && PyErr_Occurred()) {{{{
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         elif self.format_unit == 'C':
             return """
                 if (!PyUnicode_Check({argname})) {{{{
@@ -2956,7 +3030,7 @@ class int_converter(CConverter):
                     goto exit;
                 }}}}
                 {paramname} = PyUnicode_READ_CHAR({argname}, 0);
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            displayname=displayname)
         return super().parse_arg(argname, displayname)
 
@@ -2978,7 +3052,7 @@ class unsigned_int_converter(CConverter):
                 if ({paramname} == (unsigned int)-1 && PyErr_Occurred()) {{{{
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 class long_converter(CConverter):
@@ -2994,7 +3068,7 @@ class long_converter(CConverter):
                 if ({paramname} == -1 && PyErr_Occurred()) {{{{
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 class unsigned_long_converter(CConverter):
@@ -3016,7 +3090,7 @@ class unsigned_long_converter(CConverter):
                     goto exit;
                 }}}}
                 {paramname} = PyLong_AsUnsignedLongMask({argname});
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            displayname=displayname)
         return super().parse_arg(argname, displayname)
 
@@ -3033,7 +3107,7 @@ class long_long_converter(CConverter):
                 if ({paramname} == -1 && PyErr_Occurred()) {{{{
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 class unsigned_long_long_converter(CConverter):
@@ -3055,7 +3129,7 @@ class unsigned_long_long_converter(CConverter):
                     goto exit;
                 }}}}
                 {paramname} = PyLong_AsUnsignedLongLongMask({argname});
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            displayname=displayname)
         return super().parse_arg(argname, displayname)
 
@@ -3087,7 +3161,7 @@ class Py_ssize_t_converter(CConverter):
                     }}}}
                     {paramname} = ival;
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 
@@ -3114,7 +3188,7 @@ class size_t_converter(CConverter):
                 if ({paramname} == -1 && PyErr_Occurred()) {{{{
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 
@@ -3150,7 +3224,7 @@ class float_converter(CConverter):
                         goto exit;
                     }}}}
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 class double_converter(CConverter):
@@ -3172,7 +3246,7 @@ class double_converter(CConverter):
                         goto exit;
                     }}}}
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 
@@ -3189,7 +3263,7 @@ class Py_complex_converter(CConverter):
                 if (PyErr_Occurred()) {{{{
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name)
+                """.format(argname=argname, paramname=self.parser_name)
         return super().parse_arg(argname, displayname)
 
 
@@ -3274,7 +3348,7 @@ class str_converter(CConverter):
                     PyErr_SetString(PyExc_ValueError, "embedded null character");
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            displayname=displayname)
         if self.format_unit == 'z':
             return """
@@ -3296,7 +3370,7 @@ class str_converter(CConverter):
                     _PyArg_BadArgument("{{name}}", {displayname}, "str or None", {argname});
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            displayname=displayname)
         return super().parse_arg(argname, displayname)
 
@@ -3361,7 +3435,7 @@ class PyBytesObject_converter(CConverter):
                     goto exit;
                 }}}}
                 {paramname} = ({type}){argname};
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            type=self.type, displayname=displayname)
         return super().parse_arg(argname, displayname)
 
@@ -3378,7 +3452,7 @@ class PyByteArrayObject_converter(CConverter):
                     goto exit;
                 }}}}
                 {paramname} = ({type}){argname};
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            type=self.type, displayname=displayname)
         return super().parse_arg(argname, displayname)
 
@@ -3398,7 +3472,7 @@ class unicode_converter(CConverter):
                     goto exit;
                 }}}}
                 {paramname} = {argname};
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            displayname=displayname)
         return super().parse_arg(argname, displayname)
 
@@ -3514,7 +3588,7 @@ class Py_buffer_converter(CConverter):
                     _PyArg_BadArgument("{{name}}", {displayname}, "contiguous buffer", {argname});
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            displayname=displayname)
         elif self.format_unit == 's*':
             return """
@@ -3535,7 +3609,7 @@ class Py_buffer_converter(CConverter):
                         goto exit;
                     }}}}
                 }}}}
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            displayname=displayname)
         elif self.format_unit == 'w*':
             return """
@@ -3548,7 +3622,7 @@ class Py_buffer_converter(CConverter):
                     _PyArg_BadArgument("{{name}}", {displayname}, "contiguous buffer", {argname});
                     goto exit;
                 }}}}
-                """.format(argname=argname, paramname=self.name,
+                """.format(argname=argname, paramname=self.parser_name,
                            displayname=displayname)
         return super().parse_arg(argname, displayname)
 
@@ -4042,7 +4116,7 @@ class DSLParser:
     def directive_dump(self, name):
         self.block.output.append(self.clinic.get_destination(name).dump())
 
-    def directive_print(self, *args):
+    def directive_printout(self, *args):
         self.block.output.append(' '.join(args))
         self.block.output.append('\n')
 
@@ -4436,10 +4510,15 @@ class DSLParser:
             fail("Function " + self.function.name + " has an invalid parameter declaration (comma?):\n\t" + line)
         if function_args.defaults or function_args.kw_defaults:
             fail("Function " + self.function.name + " has an invalid parameter declaration (default value?):\n\t" + line)
-        if function_args.vararg or function_args.kwarg:
-            fail("Function " + self.function.name + " has an invalid parameter declaration (*args? **kwargs?):\n\t" + line)
+        if function_args.kwarg:
+            fail("Function " + self.function.name + " has an invalid parameter declaration (**kwargs?):\n\t" + line)
 
-        parameter = function_args.args[0]
+        if function_args.vararg:
+            is_vararg = True
+            parameter = function_args.vararg
+        else:
+            is_vararg = False
+            parameter = function_args.args[0]
 
         parameter_name = parameter.arg
         name, legacy, kwargs = self.parse_converter(parameter.annotation)
@@ -4447,10 +4526,17 @@ class DSLParser:
         if not default:
             if self.parameter_state == self.ps_optional:
                 fail("Can't have a parameter without a default (" + repr(parameter_name) + ")\nafter a parameter with a default!")
-            value = unspecified
+            if is_vararg:
+                value = NULL
+                kwargs.setdefault('c_default', "NULL")
+            else:
+                value = unspecified
             if 'py_default' in kwargs:
                 fail("You can't specify py_default without specifying a default value!")
         else:
+            if is_vararg:
+                fail("Vararg can't take a default value!")
+
             if self.parameter_state == self.ps_required:
                 self.parameter_state = self.ps_optional
             default = default.strip()
@@ -4570,7 +4656,12 @@ class DSLParser:
         # but the parameter object gets the python name
         converter = dict[name](c_name or parameter_name, parameter_name, self.function, value, **kwargs)
 
-        kind = inspect.Parameter.KEYWORD_ONLY if self.keyword_only else inspect.Parameter.POSITIONAL_OR_KEYWORD
+        if is_vararg:
+            kind = inspect.Parameter.VAR_POSITIONAL
+        elif self.keyword_only:
+            kind = inspect.Parameter.KEYWORD_ONLY
+        else:
+            kind = inspect.Parameter.POSITIONAL_OR_KEYWORD
 
         if isinstance(converter, self_converter):
             if len(self.function.parameters) == 1:
@@ -4664,6 +4755,8 @@ class DSLParser:
                 fail("Function " + self.function.name + " mixes keyword-only and positional-only parameters, which is unsupported.")
             # fixup preceding parameters
             for p in self.function.parameters.values():
+                if p.is_vararg():
+                    continue
                 if (p.kind != inspect.Parameter.POSITIONAL_OR_KEYWORD and not isinstance(p.converter, self_converter)):
                     fail("Function " + self.function.name + " mixes keyword-only and positional-only parameters, which is unsupported.")
                 p.kind = inspect.Parameter.POSITIONAL_ONLY
@@ -4858,10 +4951,13 @@ class DSLParser:
                 # calling the class to construct a new instance.
                 p_add('$')
 
+            if p.is_vararg():
+                p_add("*")
+
             name = p.converter.signature_name or p.name
             p_add(name)
 
-            if p.converter.is_optional():
+            if not p.is_vararg() and p.converter.is_optional():
                 p_add('=')
                 value = p.converter.py_default
                 if not value: