Re: Boehm-Demers-Weiser conservative garbage collector and GNAT

[Florian Weimer <fw@deneb.enyo.de>]

Martin Krischik <krischik@users.sourceforge.net> writes:

> I am wondering if it is possible to implement a storage pool using
> the Boehm-Demers-Weiser conservative garbage collector in GNAT.

There are a few pitfalls.  For example, objects with a controlled
component are always reachable from the collector's point of view, so
they can never be collected (in fact, the Ada semantics of
finalization mandate this behavior).  Furthermore, the collector can
hugely benefit from very basic type information (proper flagging of
pointer-free objects and objects without aliased components).

However, the real killer for the storage pool approach is the fact
that the collector will neither track properly the root set, nor task
creation.  You can solve the first problem with a custom
implementation of System.Memory (allocating all objects using the
collector); some more run-time library tweaking can solve the second.

(However, I still don't know if Boehm-Demers-Weiser collector is
actually compatible with GNAT's tasking implementation.)