It looks to me like they've allocated a pointer to an sp_session and then passed a pointer to that to sp_session_create.

My best attempt tries to do the same but comes across a missing Storable instance of the equivalent of the sp_session data structure. Because the C definition of this struct is not exposed in the header files I can't work out how to do it myself. The alternative of passing in an empty pointer with the assumption that the procedure will allocate memory for us simply segfaults.