Re: Better support for garbage collection

[Laurent Guerby <guerby@acm.org>]

Robert A Duff <bobduff@world.std.com> writes:
> Laurent Guerby <guerby@acm.org> writes:
> > What I would like to see in Ada is to have an allocator where you pass
> > the pool object at allocation and deallocation. One pool per type is
> > not very flexible.
> I agree.  I'm currently working on a tool that analyzes programs, and I
> store the symbol table for each source file in a separate storage pool,
> so I can deallocate them conveniently and efficiently as things become
> obsolete and whatnot.  It's a pain in the neck to implement that in Ada,
> and it's impossible to make it task safe (but I don't happen to need
> tasks in that part of my tool).

I'm even surprised it's possible to implement at all. How do you
manage to get one pool per file in Ada (I assume a dynamic number of
file)?

> > Why did Ada 95 include pool objects only on a per type basis?
> I don't know.  Perhaps Tucker can tell us.
> 
> What syntax would you suggest?

The obvious new T'(Pool_Object, Value) doesn't work unfortunately, so
may be:

new T'(Value) at Pool_Object -- may be replace "at" by use/of/with/in???

You also need a new version of Unchecked_Deallocation with an
additional parameter, but no new syntax needed here (and with
overloading, no new name).

I see no way to include the allocation part of this feature without
new syntax, due to the way 4.8 is written:

    4.7:
    qualified_expression ::=
       subtype_mark'(expression) | subtype_mark'aggregate

If other people have ideas.

-- 
Laurent Guerby <guerby@acm.org>