Re: Objects and the Stack?

[Dave Thompson <david.thompson1@worldnet.att.net>]

On Sat, 18 Dec 2004 14:41:33 -0500, "Warren W. Gay VE3WWG"
<ve3wwg@NoSpam.cogeco.ca> wrote:

> Nick Roberts wrote:
<snip>
> > Ada has no equivalent of alloca() in C. It might be interesting to 
> > experiment with a compiler extension to provide this facility. Certain 
> > algorithms might benefit from it.
> 
> The difference between what alloca() gets you and what you
> get in the declare block is a minor difference:
>
<snip pseudoexample>

Agree.

> >    declare
> >       Name: String := "";
> >       pragma Extensible_Object(Name);
> >    begin
> >       ...
> >       Name := Name & ':'; -- changes its size
> >       ...
> > 
> > It's an idea.
> 
> This is taking the alloca() idea further than I think it
> goes. I could be wrong here, but can you realloc() an
> alloca() region?  If so, that is something that Ada does

No. But, if you alloca() multiple times, with nothing intervening, you
can probably count on them being contiguous, although probably (on
nearly all machines) in reverse order and maybe not exactly the size
requested, and AFAICS (even) that's not formally guaranteed.

> in fact lack (including a realloc() in general, which I
> pine for when growing arrays).
> 

- David.Thompson1 at worldnet.att.net