Implicit garbage collection in Ada systems

[saharbaugh%roo.dnet@WINNIE.BERKELEY.EDU]

 On 2 Jan 91 Ken Dritz writes:
-In a chapter that I am writing for a book, I would like to say that, whereas
-Ada permits implicit garbage collection, not a single implementation of Ada
-has it.  Is that correct, as far as you know?  (I mean fully general and
-complete garbage collection, not just the freeing of the collection associated
-with an access type when the scope of the type's declaration is exited.)
-
-Actually, I need to say only that implicit garbage collection is not routinely
-implemented, which is certainly true.  Such a statement justifies the strategy
-chosen for a problem solution demonstrated in the chapter.  For added effect,
-I would like to make a stronger statement.  I could hedge and say that I am not
-aware of an Ada system that implements implicit (i.e., automatic) garbage
-collection.  Can I do better and accurately say that no Ada system implements
-it?  Does anyone know of a counterexample?

     Yes, we have a heap management system called HeapGuard (tm) which 
was invented to allow full-Ada to be used in hard real-time systems.  It is 
based on a management scheme that manages memory so that garbage 
collection is never needed.  HeapGuard can be implemented totally in 
software or can be included in a RAM memory board.  We have 
implemented it totally in software in a Verdix Ada Run-Time Environment 
on a Silicon Graphics computer system.  We have also implemented 
hardware support for HeapGuard in a custom built memory board on the 
VME bus of the Silicon Graphics computer.  
     The total software system consists of an Ada Fuzzy Expert System 
(AFES) with flight planning rules as the application.  AFES continuously 
creates "new" objects of various size on the heap and some time later 
"deallocates" them and the ARTE tells HeapGuard to allocate and deallocate 
them and the whole thing runs and runs without stopping for garbage 
collecting.
     As you can probably see I am being protective of how it works; 
however, we are looking for a real system on which to apply it.  Please 
contact me if you have an application on which it might be applicable..Since 
the research was sponsored by the Air Force there is no royalty for use on a 
Government project.  

sam harbaugh
Integrated Software, Inc.
1945 Palm Bay Rd #7
Palm Bay, Florida 32905
(407) 984-1986     fax (407) 951-4291
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