SAFEty and the Cross Referencing of BLASTs

[Mark S. Miller <vlad!mark>]

Date: Mon, 3 Dec 90 11:39:16 PST
   From: xanadu!tribble (Eric Dean Tribble)

   All SAFE methods can be NOLOCK, and some methods that are not SAFE
   will be NOLOCK (the splay routines in particular).

I see.  Makes sense.  SAFE implies NOLOCK.  SAFE also implies NOFAULT.
Is there any such relationship between NOLOCK and NOFAULT?  

   SAFE strikes me something like a type declaration:  a particular
   implementation is not safe unless all subclass implementations are
   safe (because they could be transparently substituted.

Yes, it is exactly like a type declaration.  It is a contractual
obligation which is inherited by subclasses, and which is statically
checked when a client needs something he's invoking to be SAFE
(because the invokation is happening from a SAFE routine).  This also
gives SAFE checking the kind of compositional flavor that one
associates with type checking.