pub type Udf_func_deinit = Option<unsafe extern "C" fn(arg1: *mut UDF_INIT)>;
Function signature of an xxx_deinit(...) function
xxx_deinit(...)
pub enum Udf_func_deinit { None, Some(unsafe extern "C" fn(*mut UDF_INIT)), }
No value.
Some value of type T.
T