Re: How do I get this to work??

[Jeff Carter <spam.carter.not@spam.innocon.com>]

robert_dewar@my-dejanews.com wrote:
> 
> In article <naRo2.8635$Kg6.64266@news2.telusplanet.net>,
>   warwicks@telusplanet.net (Chris Warwick) wrote:
> 
> > Of the Ada compilers I have used, the
> > unchecked_deallocation on all of them
> > was to set the pointer to 0 and carry on (i.e., no calls
> > to deallocate, no
> > storing the un-used memory for later re-allocation by the
> > Ada program). When I
> > first stumbled into this I was told that this was for
> > safety reasons. It may
> > have been that I have been using safety critical versions
> > of these Ada
> > compilers, and "standard" compilers are different...
> >
> 
> I have already discussed this with Chris. He claimed that
> VADS behaved as above, which I know to be incorrect, and
> he claimed that Alsys behaved as above. I particularly know
> the latter claim to be false, since I wrote that code! The
> one thing in Alsys that he may be referring to was that for
> certain cases of small blocks in local collections, we
> deferred collecting the storage till scope exit, but that
> is the only case where there was even a deferral of the
> free operation.
> 
> The claim that this has to do with safety is just wrong.
> 
> And as for safety critical subsets, clearly these do not
> even allow Unchecked_Deallocation in the first place.
> 
> Clearly Chris's statements here are based on
> misinformation, or misinterpretation of some kind,
> and it is important not to be mislead by them.
> 
> Unchecked_Deallocation works just fine on all Ada compilers
> and always has, it is as reliable as free in C (and indeed
> on many compilers translates directly into a free call).
> 

FWIW, the first Ada compiler I used was the Rolm compiler for the Data
General Eclipse in 1984, which claimed to be the first validated Ada-83
compiler. This machine allocated an unheard-of (in 1984) 4 GB of virtual
memory for every process. I was told that this compiler's
Unchecked_Deallocation only set the access variable to null without
reusing the allocated memory, because no one could ever use up 4 GB.
This compiler was used only for training and I never verified this
statement.

This is the only compiler I have used in the last 15 years that did not
deallocate memory. However, I was also told that this compiler was the
reason Booch included memory-managed components in his components.

There seems to be a lot of hearsay in this post ...

-- 
Jeff Carter
E-mail: carter commercial-at innocon [period | full stop] com
"We burst our pimples at you."
Monty Python & the Holy Grail