[3.12] gh-105375: Improve error handling in zoneinfo module (GH-105586) (#105612)

Fix bugs where exceptions could end up being overwritten
because of deferred error handling.

(cherry picked from commit 33c92c4)

Co-authored-by: Nikita Sobolev <[email protected]>
Co-authored-by: Erlend E. Aasland <[email protected]>

Author: 3 people

Misc/NEWS.d/next/Library/2023-06-09-21-11-28.gh-issue-105375.4Mxn7t.rst

@@ -0,0 +1 @@
+Fix bugs in :mod:`zoneinfo` where exceptions could be overwritten.

Modules/_zoneinfo.c

@@ -694,14 +694,19 @@ zoneinfo_fromutc(PyObject *obj_self, PyObject *dt)
         }
         else {
             PyObject *replace = PyObject_GetAttrString(tmp, "replace");
+            Py_DECREF(tmp);
+            if (replace == NULL) {
+                return NULL;
+            }
             PyObject *args = PyTuple_New(0);
+            if (args == NULL) {
+                Py_DECREF(replace);
+                return NULL;
+            }
             PyObject *kwargs = PyDict_New();
-
-            Py_DECREF(tmp);
-            if (args == NULL || kwargs == NULL || replace == NULL) {
-                Py_XDECREF(args);
-                Py_XDECREF(kwargs);
-                Py_XDECREF(replace);
+            if (kwargs == NULL) {
+                Py_DECREF(replace);
+                Py_DECREF(args);
                 return NULL;
             }