Function ffi_utils::test_utils::call_2_with_custom

pub unsafe fn call_2_with_custom<F, E0, E1, T0, T1>(
    ud: &mut UserData, 
    f: F
) -> Result<(T0, T1), i32> where
    F: FnOnce(*mut c_void, extern "C" fn(user_data: *mut c_void, result: *const FfiResult, _: T0::C, _: T1::C)),
    E0: Debug,
    E1: Debug,
    T0: ReprC<Error = E0>,
    T1: ReprC<Error = E1>, 

Call a FFI function and block until its callback gets called, then return the argument which were passed to that callback. Use this if the callback accepts two arguments in addition to user_data and error_code. This version of the function takes a UserData with custom inner data.