Re: Garbage collector on Ada?

[Ole-Hjalmar Kristensen <oleh@vlinux.voxelvision.no>]

"Robert I. Eachus" <rieachus@attbi.com> writes:

> Dr. Michael Paus wrote:
> 
> > Just for curiosity. Has there ever been an Ada implementation
> > besides JGNAT which uses a garbage collector?
>  Yes, Symbolics had an Ada 83 compiler with garbage collection.
> 
> 
> Pedro Menendez wrote:
> 
>  
> > Since the standard specifically allows garbage collectors,
> > it would be very strange if it was impossible to implement.
> > But it definitely appears to be atypical.
> 
> 
> Actually, the reason that most Ada compilers don't have general
> garbage collectors is that most of Ada is designed to avoid
> distributed costs. For example, if you use Ada.Strings.Unbounded, the
> standard requires that the type not leave uncollected garbage. The
> typical implementation is to use a protocol that either explicitly
> does reference counting or does copying on assignment.  That way you
> only pay a small, fixed cost if and when you use Ada.Strings.Unbounded.
> 
> Similarly most packages that create either many objects on the heap or
> large objects on the heap tend to take out their own garbage.  It
> would be nice to have a general purpose garbage collector available as
> a storage pool, such that any objects in the pool would be subject to
> garbage collection.  But I don't know of such an implementation.

Neither do I for Ada compilers. But Modula-3 has (had?) exactly that,
you can choose garbage collection or not, depending on the pool.