Re: How to get Ada to ?cross the chasm??

["Randy Brukardt" <randy@rrsoftware.com>]

"Niklas Holsti" <niklas.holsti@tidorum.invalid> wrote in message 
news:flegbrFj0qjU1@mid.individual.net...
> On 18-05-04 01:27 , Randy Brukardt wrote:
>
>   [snip]
>
>> There is no realistic chance that Ada will
>> ever be changed enough to make it amenable to GC.
>
> Ouch and wow, when did that direction change?
>
> As I remember it, for a long time the mantra was that Ada (83, 95, ...) 
> was compatible with GC, but vendors did not implement GC because there was 
> no immediate demand from the current users (chicken and egg situation).

That was the same mantra used to justify not loosening the finalization 
rules to allow early finalization. However, such a loosening had to be 
fairly restricted (one can't allow it to happen anywhere, or every Finalize 
routine would have to be protected against tasking issues -- even if no 
tasking is used for the objects in question). I believe I suggested allowing 
it anywhere that a master is finalized, assuming the object in question is 
inaccessible.

Probably the complication is why there was no appetite; the argument was 
that we needed someone implementing GC before we bother to fix the rules for 
GC. But since the rules essential prohibit useful GC, no one is going to 
implement it until they know those are going to be fixed. Ergo, no progress.

>The Ada implementations targeting the JVM or .NET were/are claimed to use 
>the GC provided by the target. Were/are these somehow "non-Ada" 
>implementations?

I'm sure they were fine. If one uses the canonical linked-list 
implementation of finalization, objects with controlled parts remain 
reachable until the appropriate master goes away -- so nothing gets 
collected. (And a similar effect is necessary regardless of how finalization 
is implemented.) There still can be an underlying GC and it can be used just 
fine -- no one said anything about it actually be able to collect much.

                    Randy.