upc_lock_t typeThe type declared is
upc_lock_t
The type upc_lock_t is an opaque UPC type. upc_lock_t is a shared
datatype with incomplete type (as defined in [ISO/IEC00 Sec 6.2.5]).
Objects
of type upc_lock_t may therefore only be manipulated through pointers.
Such objects have two states called locked and unlocked.
Two pointers to that reference the same lock object will compare as equal. The results of applying upc_phaseof(), upc_threadof(), and upc_addrfield() to such pointers are undefined.