Wrap PyIter_Send to return a struct for MSVC tailcall support

Author: markshannon

Include/internal/pycore_abstract.h

@@ -59,6 +59,14 @@ PyAPI_FUNC(int) _Py_convert_optional_to_non_negative_ssize_t(PyObject *, void *)
 // Export for 'math' shared extension.
 PyAPI_FUNC(PyObject*) _PyNumber_Index(PyObject *o);
 
+typedef struct {
+    PyObject *object;
+    PySendResult kind;
+} PySendResultPair;
+
+// Same as PyIter_Send but returns a struct for MSVC tailcall support
+PyAPI_FUNC(PySendResultPair) _PyIter_Send(PyObject *iter, PyObject *arg);
+
 #ifdef __cplusplus
 }
 #endif

Modules/_testinternalcapi/test_cases.c.h

@@ -2951,3 +2951,11 @@ PyIter_Send(PyObject *iter, PyObject *arg, PyObject **result)
     }
     return PYGEN_ERROR;
 }
+
+PySendResultPair
+_PyIter_Send(PyObject *iter, PyObject *arg)
+{
+    PySendResultPair pair;
+    pair.kind = PyIter_Send(iter, arg, &pair.object);
+    return pair;
+}

Objects/abstract.c

@@ -1705,15 +1705,14 @@ dummy_func(
                 DEAD(v);
             }
             else {
-                PyObject *retval_o;
                 PyObject *v_o = PyStackRef_AsPyObjectBorrow(v);
-                PySendResult what = PyIter_Send(receiver_o, v_o, &retval_o);
-                if (what == PYGEN_ERROR) {
+                PySendResultPair res = _PyIter_Send(receiver_o, v_o);
+                if (res.kind == PYGEN_ERROR) {
                     ERROR_NO_POP();
                 }
                 PyStackRef_CLOSE(v);
-                retval = PyStackRef_FromPyObjectSteal(retval_o);
-                if (what == PYGEN_RETURN) {
+                retval = PyStackRef_FromPyObjectSteal(res.object);
+                if (res.kind == PYGEN_RETURN) {
                     JUMPBY(oparg);
                 }
             }