[gclist] Integrating GC and Destructors (Finalizers?)

[Peter Froehlich]

Hi there!

I'm  new  to  this  list.   Frank Copeland gave me it's address because I'm
currently   researching   the  indicated  subject  but  can't  find  enough
publications for a good overview or solution.

   I give quit a long "statement" on what I'm trying to do below.  Sorry if
this is too long for this list.

----- PROBLEM -----

I'm  working  on  an  extended version of the Oberon-2 programming language
called  "Froderon"  for  my diploma thesis in computer science.  The thesis
involves  implementing  a working "Froderon" compiler on top of an Oberon-2
compiler, so it's not purely theoretical.

   Oberon-2   features  GC,  usually  implemented  using  a  mark-and-sweep
algorithm.   Since  I  also  have  a  C++  background (and came to like the
constructor/destructor  "stuff"  it  provides) I thought it would be a good
idea  to incorporate destructors into Oberon-2 (and constructors of course,
for symmetry).

   A "destructor" as I see it is just a specially marked method (type-bound
procedure  in  "Oberon-2 speech") which will be called by the GC during the
sweep phase.

   The  problem  I'm facing is determining or rather guaranteeing a certain
order  in  which  the  objects  will  be  "destroyed",  ie.   the  order of
destructor-calls made by the GC in a network of objects.

   Since  I  can't  see  a  way  to  guarantee an order without introducing
"strange"  things  (eg.  priorities on pointers) into the language, I'm now
pretty much convinced that the sentence "The order in which destructors are
called  are  implementation  dependent"  will  make  it  into  the language
definition.

   However  I  doubt  that the whole concept will be very useful if I can't
guarantee an order in the first place.

----- PROBLEM -----

   If  you  know  of any publications related to GC and treating the matter
(maybe even my problem) well and in-depth, please mail me about it.  If you
have  any  other  idea or know of a language in the ALGOL family where this
problem  has been solved somehow, please also mail me or just answer to the
list.

   As  you  might  have noticed in the subject line, I'm not sure where the
exact difference between "destructor" and "finalizer" lies.  Please explain
or hint me at a suitable FAQ file.

   Thanks for taking your time.

By(T)e...
         Peter...