`val itimer_real : int`
`val itimer_virtual : int`
`val itimer_prof : int`

`type fd_set`

`val fd_set : fd_set Ctypes.typ`
`val fd_setsize : int`
`val clock_monotonic : Posix_types.clockid_t`
`val clock_realtime : Posix_types.clockid_t`
`val clock_process_cputime_id : Posix_types.clockid_t`
`val clock_thread_cputime_id : Posix_types.clockid_t`

`module Def : functor (S : Cstubs.Types.TYPE) -> sig ... end`