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From: IVANOVIC%VAXR@CIRCUS.LLNL.GOV ("Vladimir Ivanovic, x3-7786")
Newsgroups: comp.lang.ada
Subject: Pragma SHARED, tasks and shared variables
Message-ID: <8807280055.AA27279@ajpo.sei.cmu.edu>
Date: 28 Jul 88 01:03:00 GMT
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List-Id: <comp.lang.ada>


    Can anyone answer the following question:
    
    If I specify that every read or update to an variable whose type is an
    access type is a synchronization point for that variable by using the
    pragma SHARED and naming that variable [LRM 9.11(7)], can I be assured
    that the object designated by that variable will never be a local
    copy of that object?
    
    My intent is to get around the restrictions imposed by LRM 9.11(3)
    and 9.11(8) by having shared data structures whose types are not
    restricted to scalar and access types.
    
    My motivation is performance.  I cannot afford the CPU strokes that
    encapsulating the data structures in a task and performing rendezvous
    with that task to access the data would cost.  (And I cannot afford a
    faster CPU...)
    
    I realize that my particular implementation (VAX Ada v1.4) allows
    the use of pragma VOLATILE which is the same as pragma SHARED without
    the words "and whose type is a scalar or access type", essentially
    giving me what I want, but pragma VOLATILE is not portable across
    implementations.