Re: Libraries written in Ada

[Thomas Lotze <thomas@thomas-lotze.de>]

On Tue, 23 Nov 2004 13:36:02 +0100, Martin Krischik wrote:

> You can restrict packages to not use specific elaboations:
> 
> pragma Pure ();
> pragma Preelaboreate ();
> 
> The pragmas are for the Annex E where these things are more important than
> in normal development.

Ah, now I found what I was looking for. The ARM really makes for some
reading...

>> So it's not possible to reset a package in the midst of program
>> execution? If so, is it a conscious design decision, and what's the
>> rationale? (The solution seems to be offering reset functionality in the
>> package.)
> 
> A conscious design decision:
> 
> package
>   Test
> is
> 
>    Y : constant Integer = X (...);
> 
> end Test;
>  
> Do I have to explain it or do you spot it yourself ;-) .

The value of the constant might be different after a hypothetical
re-elaboration. So there would still be no problem if a constant was
understood to not change its value _after_ elaboration. In your example
I'd have a constant of unknown value anyway (or X() would have to always
yield the same value, in which case we'd be discussing a non-existing
problem), so you'd be just as fine after a re-elaboration as before
provided you treat such an event as a kind of Big Bang and never try to
connect information from after it with information from before. But I do
admit that this would be a potential well of grief.

> With GNAT the binder will automaticly generate the needed code just like
> with adainit ().
> 
> The code generated by the binder is stored in some b~ file. It is a normal
> Ada source code. In Ada only programms the binder output is deleted
> imediatly after linking - in mixed language development the binder output
> is not deleted.

Yes, I've seen such files. It is possible that adafinal() consists of just
one call to Do_Finalize. Can it be omitted in that case? Neither the ARM
nor the GNAT RM or UG seem to explain it.

> package Interface.C.Strings is only Preelaborate and package Ada.Text_IO
> is unmarked.
> 
> And if a package is unmarked then you have to expect both init and term.

Too bad.

-- 
Viele Gr��e,
Thomas