Re: GC in Ada

[Maciej Sobczak <no.spam@no.spam.com>]

Markus E Leypold wrote:

>>>> I don't understand. There is no legal way for the program to verify
>>>> that anything was indeed deallocated, so it doesn't make much sense to
>>>> say that this behaviour is required.
> 
> This is a 'non sequitur', since it makes sense to say the behaviour is
> required to fix certain real time properties. Regardless of wether it
> can be detected in the program (and it could, by observing the wall
> clock).

Observing the wall clock does not help much in a language where even 
null; can raise exceptions. Standard does not even guarantee that any 
given sequence of instructions will give consistent timings when run twice.

Definitely, observice the wall clock is of no use to verify memory 
deallocation, since deallocation might have positive effect on the 
timing as well as negative or none at all.

>> As was already pointed out in this thread, with some operating systems
>> memory reclamation might not be meaningful at all unless the whole
>> program is terminated.
> 
> I don't even ask to be shown such an operating system...

On systems with virtual memory, deallocations that don't span at least 
one full page (that condition can be met after joining with other free 
blocks, though) will certainly not deallocate anything to the operating 
system.


-- 
Maciej Sobczak : http://www.msobczak.com/
Programming    : http://www.msobczak.com/prog/