@@ -0,0 +1,3 @@
+Harden :mod:`pyexpat` error handling during module initialisation to prevent
+exceptions from possibly being overwritten, and objects from being
+dereferenced twice.
@@ -1768,14 +1768,18 @@ add_error(PyObject *errors_module, PyObject *codes_dict,
 static int
 add_errors_module(PyObject *mod)
 {
+    // add_submodule() returns a borrowed ref.
     PyObject *errors_module = add_submodule(mod, MODULE_NAME ".errors");
     if (errors_module == NULL) {
         return -1;
     }
 
     PyObject *codes_dict = PyDict_New();
+    if (codes_dict == NULL) {
+        return -1;
+    }
     PyObject *rev_codes_dict = PyDict_New();
-    if (codes_dict == NULL || rev_codes_dict == NULL) {
+    if (rev_codes_dict == NULL) {
         goto error;
     }
 
@@ -1796,19 +1800,17 @@ add_errors_module(PyObject *mod)
         goto error;
     }
 
-    Py_INCREF(codes_dict);
-    if (PyModule_AddObject(errors_module, "codes", codes_dict) < 0) {
-        Py_DECREF(codes_dict);
+    int rc = PyModule_AddObjectRef(errors_module, "codes", codes_dict);
+    Py_CLEAR(codes_dict);
+    if (rc < 0) {
         goto error;
     }
-    Py_CLEAR(codes_dict);
 
-    Py_INCREF(rev_codes_dict);
-    if (PyModule_AddObject(errors_module, "messages", rev_codes_dict) < 0) {
-        Py_DECREF(rev_codes_dict);
+    rc = PyModule_AddObjectRef(errors_module, "messages", rev_codes_dict);
+    Py_CLEAR(rev_codes_dict);
+    if (rc < 0) {
         goto error;
     }
-    Py_CLEAR(rev_codes_dict);
 
     return 0;
Original file line number	Diff line number	Diff line change
@@ -0,0 +1,3 @@
	1	+ Harden :mod:`pyexpat` error handling during module initialisation to prevent
	2	+ exceptions from possibly being overwritten, and objects from being
	3	+ dereferenced twice.