[3.12] gh-129573: Fix abort from non-string suggestions in calculate_suggestions

Lib/test/test_traceback.py

@@ -3166,6 +3166,17 @@ class A:
         actual = self.get_suggestion(A(), 'bluch')
         self.assertNotIn("blech", actual)
 
+    def test_suggestions_do_not_trigger_with_non_string_candidates(self):
+        class Parent:
+            def __dir__(self):
+                return [0]
+
+        class WithNonStringAttrs(Parent):
+            blech = None
+
+        result = self.get_suggestion(WithNonStringAttrs(), "bluch")
+        self.assertNotIn(result, "blech")
+
     def test_getattr_suggestions_no_args(self):
         class A:
             blech = None

Python/suggestions.c

@@ -151,6 +151,10 @@ calculate_suggestions(PyObject *dir,
     }
     for (int i = 0; i < dir_size; ++i) {
         PyObject *item = PyList_GET_ITEM(dir, i);
+        if (!PyUnicode_Check(item)) {
+            PyMem_Free(buffer);
+            return NULL;
+        }
         if (_PyUnicode_Equal(name, item)) {
             continue;
         }