[Bugfix] Prevent segfault when instantiating abstract SearchStrategy

python/tvm/meta_schedule/search_strategy/search_strategy.py

@@ -87,6 +87,21 @@ class SearchStrategy(Object):
         ],
     ]
 
+    def __new__(cls, *args, **kwargs):  # pylint: disable=unused-argument
+        """Prevent direct instantiation of abstract SearchStrategy class.
+
+        SearchStrategy is an abstract class and cannot be directly instantiated.
+        Use SearchStrategy.create() or a concrete subclass instead.
+        """
+        if cls is SearchStrategy:
+            raise TypeError(
+                "Cannot instantiate abstract class SearchStrategy. "
+                "Use SearchStrategy.create() with a valid strategy type "
+                "(e.g., 'evolutionary', 'replay-trace', 'replay-func') "
+                "or use a concrete subclass instead."
+            )
+        return super().__new__(cls)  # pylint: disable=no-value-for-parameter
+
     def _initialize_with_tune_context(self, context: "TuneContext") -> None:
         """Initialize the search strategy with tuning context.
 

python/tvm/meta_schedule/tune_context.py

@@ -123,6 +123,15 @@ def __init__(
         if search_strategy is not None:
             if not isinstance(search_strategy, SearchStrategy):
                 search_strategy = SearchStrategy.create(search_strategy)
+            # Additional check: ensure it's not the abstract SearchStrategy class itself
+            # Use type() for exact type check (not isinstance which would match subclasses)
+            elif type(search_strategy) is SearchStrategy:  # pylint: disable=unidiomatic-typecheck
+                raise TypeError(
+                    "Cannot use abstract SearchStrategy class directly. "
+                    "Use SearchStrategy.create() with a valid strategy type "
+                    "(e.g., 'evolutionary', 'replay-trace', 'replay-func') "
+                    "or use a concrete subclass instead."
+                )
         if logger is None:
             logger = get_logger(__name__)
         if not isinstance(num_threads, int):

tests/python/meta_schedule/test_meta_schedule_search_strategy.py

@@ -306,9 +306,40 @@ def __str__(self) -> str:
     assert candidates is None
 
 
+def test_search_strategy_abstract_class_instantiation():
+    """Test that directly instantiating abstract SearchStrategy raises TypeError instead of segfault."""
+    from tvm.meta_schedule import SearchStrategy
+    from tvm.target import Target
+    from tvm.meta_schedule import TuneContext
+
+    # Test that direct instantiation raises TypeError
+    # This prevents segfault when SearchStrategy() is called directly
+    with pytest.raises(TypeError, match="Cannot instantiate abstract class SearchStrategy"):
+        SearchStrategy()
+
+    # Test that TuneContext with SearchStrategy() raises TypeError
+    # The error should occur when trying to create SearchStrategy() instance in the function call
+    # Since SearchStrategy() fails in __new__, it will fail before TuneContext.__init__ is called
+    with pytest.raises(TypeError, match="Cannot instantiate abstract class SearchStrategy"):
+        # This will fail when evaluating SearchStrategy() as an argument
+        TuneContext(
+            mod=Matmul,  # Use the existing Matmul module from the test file
+            target=Target("llvm"),
+            search_strategy=SearchStrategy(),  # This should fail in __new__ before reaching TuneContext
+        )
+
+    # Test that SearchStrategy.create() works correctly
+    strategy = SearchStrategy.create("evolutionary")
+    assert strategy is not None
+    assert isinstance(strategy, SearchStrategy)
+    # Verify it's not the abstract class itself
+    assert type(strategy) is not SearchStrategy
+
+
 if __name__ == "__main__":
     test_meta_schedule_replay_func(ms.search_strategy.ReplayFunc)
     test_meta_schedule_replay_func(ms.search_strategy.ReplayTrace)
     test_meta_schedule_evolutionary_search()
     test_meta_schedule_evolutionary_search_early_stop()
     test_meta_schedule_evolutionary_search_fail_init_population()
+    test_search_strategy_abstract_class_instantiation()