fix(python/adbc_driver_manager): prevent segfault in _AdbcErrorHelper.check_error

python/adbc_driver_manager/adbc_driver_manager/_reader.pyi

@@ -32,3 +32,6 @@ class AdbcRecordBatchReader(pyarrow.RecordBatchReader):
     def __enter__(self) -> AdbcRecordBatchReader: ...
     def __exit__(self, type, value, traceback) -> None: ...
     def __iter__(self) -> typing.Iterator[pyarrow.RecordBatch]: ...
+
+class _AdbcErrorHelper:
+    def check_error(self, exception: Exception) -> None: ...

python/adbc_driver_manager/adbc_driver_manager/_reader.pyx

@@ -30,6 +30,9 @@ cdef class _AdbcErrorHelper:
         CArrowArrayStream c_stream
 
     def check_error(self, exception):
+        if self.c_stream.release == NULL:
+            raise exception
+
         cdef:
             CAdbcStatusCode c_status = ADBC_STATUS_OK
             const CAdbcError* error = \

python/adbc_driver_manager/tests/test_reader.py

@@ -78,3 +78,19 @@ def test_reader_methods() -> None:
 
     with _make_reader() as reader:
         assert reader.schema == schema
+
+
+def test_check_error_with_released_stream():
+    """check_error must re-raise when c_stream.release is NULL."""
+    from adbc_driver_manager._reader import _AdbcErrorHelper
+
+    # Default-constructed helper has a zeroed c_stream (release == NULL)
+    helper = _AdbcErrorHelper.__new__(_AdbcErrorHelper)
+
+    err = ValueError("upstream error")
+    with pytest.raises(ValueError, match="upstream error"):
+        helper.check_error(err)
+
+    err = pyarrow.ArrowInvalid("Invalid or unsupported format string: 'd:5,2,32'")
+    with pytest.raises(pyarrow.ArrowInvalid, match="unsupported format string"):
+        helper.check_error(err)