bpo-35441: Remove dead and buggy code related to PyList_SetItem(). (GH-11033)


In _localemodule.c and selectmodule.c, remove dead code that would
cause double decrefs if run.

In addition, replace PyList_SetItem() with PyList_SET_ITEM() in cases
where a new list is populated and there is no possibility of an error.

In addition, check if the list changed size in the loop in array_array_fromlist().
(cherry picked from commit 99d56b53560b3867844472ae381fb3f858760621)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>
diff --git a/Modules/_localemodule.c b/Modules/_localemodule.c
index 716a730..8efda35 100644
--- a/Modules/_localemodule.c
+++ b/Modules/_localemodule.c
@@ -70,20 +70,13 @@
     do {
         i++;
         val = PyLong_FromLong(s[i]);
-        if (!val)
-            break;
-        if (PyList_SetItem(result, i, val)) {
-            Py_DECREF(val);
-            val = NULL;
-            break;
+        if (val == NULL) {
+            Py_DECREF(result);
+            return NULL;
         }
+        PyList_SET_ITEM(result, i, val);
     } while (s[i] != '\0' && s[i] != CHAR_MAX);
 
-    if (!val) {
-        Py_DECREF(result);
-        return NULL;
-    }
-
     return result;
 }