Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!udel!gatech!hubcap!billwolf%hazel.cs.clemson.edu
From: billwolf%hazel.cs.clemson.edu@hubcap.clemson.edu (William Thomas Wolfe, 2847 )
Newsgroups: comp.sw.components
Subject: Re:  Re: Real-time Garbage Collection
Message-ID: <6519@hubcap.clemson.edu>
Date: 20 Sep 89 14:46:24 GMT
References: <896@scaup.cl.cam.ac.uk>
Sender: news@hubcap.clemson.edu
Reply-To: billwolf%hazel.cs.clemson.edu@hubcap.clemson.edu
Lines: 23

From scc@cl.cam.ac.uk (Stephen Crawley):
>>>> It's safe to [reclaim a dynamicly allocated ADT]:
>>>>  1) When the variable goes out of scope
>>>>  2) When the programmer specifies that it's to be destroyed sooner.
>>   [...] the basic thrust of the position is that the programmer
>>   should generally not use pointers explicitly; rather, the use of 
>>   pointers should be made safe via encapsulation within a secure ADT.
>    
> It makes no difference whether references to an ADT is implicit 
> or explicit.  The ADT cannot know whether or not the application 
> that uses it still holds a reference to a given instance.

    The pointers are INTERNAL to the ADT, and the user will never
    see them.  When the ADT goes out of scope, it dies just like 
    any predefined type would.  We are considering here an ADT which 
    is declared at the beginning of a (procedure, function, block).
    This ADT will do dynamic allocation INTERNALLY so as to facilitate
    its own expansion and contraction as necessary.  Upon block exit, 
    the ADT's destroy procedure will be invoked, and all the space
    occupied by the ADT will be released.

    
    Bill Wolfe, wtwolfe@hubcap.clemson.edu