gh-102471: Change PyLongWriter_Discard(NULL) to do nothing (#129339)

vstinner · web-flow · commit 7ec17429d462 · 2025-01-27T10:51:16.000Z
It's convenient to be able to call PyLongWriter_Discard(NULL) in
error handling code.
diff --git a/Doc/c-api/long.rst b/Doc/c-api/long.rst
@@ -824,6 +824,6 @@ The :c:type:`PyLongWriter` API can be used to import an integer.
 
    Discard a :c:type:`PyLongWriter` created by :c:func:`PyLongWriter_Create`.
 
-   *writer* must not be ``NULL``.
+   If *writer* is ``NULL``, no operation is performed.
 
    The writer instance and the *digits* array are invalid after the call.
diff --git a/Objects/longobject.c b/Objects/longobject.c
@@ -6953,6 +6953,10 @@ PyLongWriter_Create(int negative, Py_ssize_t ndigits, void **digits)
 void
 PyLongWriter_Discard(PyLongWriter *writer)
 {
+    if (writer == NULL) {
+        return;
+    }
+
     PyLongObject *obj = (PyLongObject *)writer;
     assert(Py_REFCNT(obj) == 1);
     Py_DECREF(obj);
