gh-108494: Argument Clinic partial supports of Limited C API (#108495)

Argument Clinic now has a partial support of the
Limited API:

* Add --limited option to clinic.c.
* Add '_testclinic_limited' extension which is built with
  the limited C API version 3.13.
* For now, hardcode in clinic.py that "_testclinic_limited.c" targets
  the limited C API.

Modules/Setup.stdlib.in

@@ -161,6 +161,7 @@
 @MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c
 @MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/vectorcall_limited.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyos.c _testcapi/immortal.c _testcapi/heaptype_relative.c _testcapi/gc.c
 @MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c
+@MODULE__TESTCLINIC_TRUE@_testclinic_limited _testclinic_limited.c
 
 # Some testing modules MUST be built as shared libraries.
 *shared*

Modules/_testclinic_limited.c

@@ -0,0 +1,69 @@
+// For now, only limited C API 3.13 is supported
+#define Py_LIMITED_API 0x030d0000
+
+/* Always enable assertions */
+#undef NDEBUG
+
+#include "Python.h"
+
+
+#include "clinic/_testclinic_limited.c.h"
+
+
+/*[clinic input]
+module  _testclinic_limited
+[clinic start generated code]*/
+/*[clinic end generated code: output=da39a3ee5e6b4b0d input=dd408149a4fc0dbb]*/
+
+
+/*[clinic input]
+test_empty_function
+
+[clinic start generated code]*/
+
+static PyObject *
+test_empty_function_impl(PyObject *module)
+/*[clinic end generated code: output=0f8aeb3ddced55cb input=0dd7048651ad4ae4]*/
+{
+    Py_RETURN_NONE;
+}
+
+
+/*[clinic input]
+my_int_func -> int
+
+    arg: int
+    /
+
+[clinic start generated code]*/
+
+static int
+my_int_func_impl(PyObject *module, int arg)
+/*[clinic end generated code: output=761cd54582f10e4f input=16eb8bba71d82740]*/
+{
+    return arg;
+}
+
+
+static PyMethodDef tester_methods[] = {
+    TEST_EMPTY_FUNCTION_METHODDEF
+    MY_INT_FUNC_METHODDEF
+    {NULL, NULL}
+};
+
+static struct PyModuleDef _testclinic_module = {
+    PyModuleDef_HEAD_INIT,
+    .m_name = "_testclinic_limited",
+    .m_size = 0,
+    .m_methods = tester_methods,
+};
+
+PyMODINIT_FUNC
+PyInit__testclinic_limited(void)
+{
+    PyObject *m = PyModule_Create(&_testclinic_module);
+    if (m == NULL) {
+        return NULL;
+    }
+    return m;
+}

Modules/clinic/_testclinic_limited.c.h

@@ -0,0 +1,53 @@
+/*[clinic input]
+preserve
+[clinic start generated code]*/
+
+PyDoc_STRVAR(test_empty_function__doc__,
+"test_empty_function($module, /)\n"
+"--\n"
+"\n");
+
+#define TEST_EMPTY_FUNCTION_METHODDEF    \
+    {"test_empty_function", (PyCFunction)test_empty_function, METH_NOARGS, test_empty_function__doc__},
+
+static PyObject *
+test_empty_function_impl(PyObject *module);
+
+static PyObject *
+test_empty_function(PyObject *module, PyObject *Py_UNUSED(ignored))
+{
+    return test_empty_function_impl(module);
+}
+
+PyDoc_STRVAR(my_int_func__doc__,
+"my_int_func($module, arg, /)\n"
+"--\n"
+"\n");
+
+#define MY_INT_FUNC_METHODDEF    \
+    {"my_int_func", (PyCFunction)my_int_func, METH_O, my_int_func__doc__},
+
+static int
+my_int_func_impl(PyObject *module, int arg);
+
+static PyObject *
+my_int_func(PyObject *module, PyObject *arg_)
+{
+    PyObject *return_value = NULL;
+    int arg;
+    int _return_value;
+
+    arg = PyLong_AsInt(arg_);
+    if (arg == -1 && PyErr_Occurred()) {
+        goto exit;
+    }
+    _return_value = my_int_func_impl(module, arg);
+    if ((_return_value == -1) && PyErr_Occurred()) {
+        goto exit;
+    }
+    return_value = PyLong_FromLong((long)_return_value);
+
+exit:
+    return return_value;
+}
+/*[clinic end generated code: output=07e2e8ed6923cd16 input=a9049054013a1b77]*/