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().

1 files changed, 4 insertions, 11 deletions

diff --git a/Modules/_localemodule.c b/Modules/_localemodule.c
index 4202cc4..96ca68a 100644
--- a/Modules/_localemodule.c
+++ b/Modules/_localemodule.c
@@ -71,20 +71,13 @@ copy_grouping(const char* s)
     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;
 }