Add initial version of _PyTuple_FromPair

Author: sergey-miryanov

Include/internal/pycore_tuple.h

@@ -26,6 +26,9 @@ extern PyStatus _PyTuple_InitGlobalObjects(PyInterpreterState *);
 PyAPI_FUNC(PyObject *)_PyTuple_FromStackRefStealOnSuccess(const union _PyStackRef *, Py_ssize_t);
 PyAPI_FUNC(PyObject *)_PyTuple_FromArraySteal(PyObject *const *, Py_ssize_t);
 
+PyAPI_FUNC(PyObject *)_PyTuple_FromPair(PyObject *, PyObject *);
+PyAPI_FUNC(PyObject *)_PyTuple_FromPairSteal(PyObject *, PyObject *);
+
 typedef struct {
     PyObject_HEAD
     Py_ssize_t it_index;

Objects/tupleobject.c

@@ -202,6 +202,59 @@ PyTuple_Pack(Py_ssize_t n, ...)
     return (PyObject *)result;
 }
 
+static PyTupleObject *
+tuple_alloc_2()
+{
+    Py_ssize_t size = 2;
+    Py_ssize_t index = size - 1;
+    assert(index < PyTuple_MAXSAVESIZE);
+    PyTupleObject *result = _Py_FREELIST_POP(PyTupleObject, tuples[index]);
+    if (result == NULL) {
+        result = PyObject_GC_NewVar(PyTupleObject, &PyTuple_Type, size);
+    }
+    if (result != NULL) {
+        _PyTuple_RESET_HASH_CACHE(result);
+    }
+    return result;
+}
+
+PyObject *
+_PyTuple_FromPair(PyObject *one, PyObject *two)
+{
+    assert (one != NULL);
+    assert (two != NULL);
+
+    PyTupleObject *op = tuple_alloc_2();
+    if (op == NULL) {
+        return NULL;
+    }
+    op->ob_item[0] = Py_NewRef(one);
+    op->ob_item[1] = Py_NewRef(two);
+    if (maybe_tracked(one) || maybe_tracked(two)) {
+        _PyObject_GC_TRACK(op);
+    }
+    return (PyObject *)op;
+}
+
+PyObject *
+_PyTuple_FromPairSteal(PyObject *one, PyObject *two)
+{
+    assert (one != NULL);
+    assert (two != NULL);
+
+    PyTupleObject *op = tuple_alloc_2();
+    if (op == NULL) {
+        Py_DECREF(one);
+        Py_DECREF(two);
+        return NULL;
+    }
+    op->ob_item[0] = one;
+    op->ob_item[1] = two;
+    if (maybe_tracked(one) || maybe_tracked(two)) {
+        _PyObject_GC_TRACK(op);
+    }
+    return (PyObject *)op;
+}
 
 /* Methods */