Function test_error_no_cyclic_reference

tests/python/test_error.py:120–153

()

def test_error_no_cyclic_reference() -> None:
    # This test case ensures that when an error is raised from C++ side,
    # there is no cyclic reference that slows down the garbage collection.
    # Please see `_with_append_backtrace` in error.py

    # temporarily disable gc
    gc.disable()

    try:
        # We should create a class as a probe to detect gc activity
        # beacuse weakref doesn't support list, dict or other trivial types
        class SampleObject: ...

        # trigger a C++ side KeyError by accessing a non-existent key
        def trigger_cpp_side_error() -> None:
            try:
                tmp_map: tvm_ffi.Map = tvm_ffi.Map(dict())
                tmp_map["a"]
            except KeyError:
                pass

        def may_create_cyclic_reference() -> weakref.ReferenceType:
            obj = SampleObject()
            trigger_cpp_side_error()
            return weakref.ref(obj)

        wref = may_create_cyclic_reference()

        # if the object is not collected, wref() will return the object
        assert wref() is None, "Cyclic reference occurs inside error handling pipeline"

    finally:
        # re-enable gc whenever exception occurs
        gc.enable()