Issue #20185: Convert _warnings.warn() to Argument Clinic
Fix warn_explicit(): interpret source=None as source=NULL.
diff --git a/Python/clinic/_warnings.c.h b/Python/clinic/_warnings.c.h
new file mode 100644
index 0000000..db2245c
--- /dev/null
+++ b/Python/clinic/_warnings.c.h
@@ -0,0 +1,38 @@
+/*[clinic input]
+preserve
+[clinic start generated code]*/
+
+PyDoc_STRVAR(warnings_warn__doc__,
+"warn($module, /, message, category=None, stacklevel=1, source=None)\n"
+"--\n"
+"\n"
+"Issue a warning, or maybe ignore it or raise an exception.");
+
+#define WARNINGS_WARN_METHODDEF \
+ {"warn", (PyCFunction)warnings_warn, METH_FASTCALL, warnings_warn__doc__},
+
+static PyObject *
+warnings_warn_impl(PyObject *module, PyObject *message, PyObject *category,
+ Py_ssize_t stacklevel, PyObject *source);
+
+static PyObject *
+warnings_warn(PyObject *module, PyObject **args, Py_ssize_t nargs, PyObject *kwnames)
+{
+ PyObject *return_value = NULL;
+ static const char * const _keywords[] = {"message", "category", "stacklevel", "source", NULL};
+ static _PyArg_Parser _parser = {"O|OnO:warn", _keywords, 0};
+ PyObject *message;
+ PyObject *category = Py_None;
+ Py_ssize_t stacklevel = 1;
+ PyObject *source = Py_None;
+
+ if (!_PyArg_ParseStack(args, nargs, kwnames, &_parser,
+ &message, &category, &stacklevel, &source)) {
+ goto exit;
+ }
+ return_value = warnings_warn_impl(module, message, category, stacklevel, source);
+
+exit:
+ return return_value;
+}
+/*[clinic end generated code: output=b3c5297c2c55778c input=a9049054013a1b77]*/