Genode is new to me . I just start playing with it. 

I was looking  at the Hello program and the RPC mechanism.  as i understood RPC does not support passing pointer as parameter 

how i can pass a parameter by reference where i need to change its value in the server side. 

I found in the rpc.h  that the parameter could be input and output in the same time. How i can  use this ? are there any  implemented examples . 

should i defined an  my output structure  if the remote procedure return multiple outputs.   

best.