gh-114329: Add `PyList_GetItemRef` function (GH-114504)

The new `PyList_GetItemRef` is similar to `PyList_GetItem`, but returns
a strong reference instead of a borrowed reference. Additionally, if the
passed "list" object is not a list, the function sets a `TypeError`
instead of calling `PyErr_BadInternalCall()`.

1 files changed, 15 insertions, 0 deletions

diff --git a/Objects/listobject.c b/Objects/listobject.c
index da2b9cc..82a4ba9 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -257,6 +257,21 @@ PyList_GetItem(PyObject *op, Py_ssize_t i)
     return ((PyListObject *)op) -> ob_item[i];
 }
 
+PyObject *
+PyList_GetItemRef(PyObject *op, Py_ssize_t i)
+{
+    if (!PyList_Check(op)) {
+        PyErr_SetString(PyExc_TypeError, "expected a list");
+        return NULL;
+    }
+    if (!valid_index(i, Py_SIZE(op))) {
+        _Py_DECLARE_STR(list_err, "list index out of range");
+        PyErr_SetObject(PyExc_IndexError, &_Py_STR(list_err));
+        return NULL;
+    }
+    return Py_NewRef(PyList_GET_ITEM(op, i));
+}
+
 int
 PyList_SetItem(PyObject *op, Py_ssize_t i,
                PyObject *newitem)