Macro sem::semop

macro_rules! semop {
    ($id: expr, $lock: expr) => { ... };
    ($id: expr, $index: expr, $lock: expr) => { ... };
    ($id: expr, $index: expr, $lock: expr, $nbop: expr) => { ... };
    ($id: expr, $index: expr, $lock: expr, $nbop: expr, $flag: expr) => { ... };
}

The semop macro sets the semaphore index according to a SemBuffer.