gh-124074: Add _Py_NewImmortalRef() function

Include/internal/pycore_long.h

@@ -63,12 +63,12 @@ extern void _PyLong_FiniTypes(PyInterpreterState *interp);
 #  error "_PY_NSMALLPOSINTS must be greater than or equal to 257"
 #endif
 
-// Return a reference to the immortal zero singleton.
+// Return a borrowed reference to the immortal zero singleton.
 // The function cannot return NULL.
 static inline PyObject* _PyLong_GetZero(void)
 { return (PyObject *)&_PyLong_SMALL_INTS[_PY_NSMALLNEGINTS]; }
 
-// Return a reference to the immortal one singleton.
+// Return a borrowed reference to the immortal one singleton.
 // The function cannot return NULL.
 static inline PyObject* _PyLong_GetOne(void)
 { return (PyObject *)&_PyLong_SMALL_INTS[_PY_NSMALLNEGINTS+1]; }

Include/internal/pycore_object.h

@@ -874,6 +874,15 @@ PyAPI_DATA(int) _Py_SwappedOp[];
 
 extern void _Py_GetConstant_Init(void);
 
+
+// Similar to Py_NewRef() but for immortal objects.
+// obj must be immortal.
+static inline PyObject* _Py_NewImmortalRef(PyObject *obj)
+{
+    assert(_Py_IsImmortalLoose(obj));
+    return obj;
+}
+
 #ifdef __cplusplus
 }
 #endif

Objects/boolobject.c

@@ -20,7 +20,8 @@ bool_repr(PyObject *self)
 
 PyObject *PyBool_FromLong(long ok)
 {
-    return ok ? Py_True : Py_False;
+    PyObject *result = ok ? Py_True : Py_False;
+    return _Py_NewImmortalRef(result);
 }
 
 /* We define bool_new to always return either Py_True or Py_False */

Objects/object.c

@@ -3025,7 +3025,7 @@ PyObject*
 Py_GetConstant(unsigned int constant_id)
 {
     if (constant_id < Py_ARRAY_LENGTH(constants)) {
-        return constants[constant_id];
+        return _Py_NewImmortalRef(constants[constant_id]);
     }
     else {
         PyErr_BadInternalCall();