Re: Export instances of procedures

[Vincent Marciante <marciant@li.net>]

Gautier wrote:
> 
> Vincent Marciante wrote:
> 
> > At this point, Read_8bit_AutoInt(...) requires a completion.
> > A subprogram renaming declaration (RM 8.5.4) can act as a completion but
> > an instantiation can't.
> 
> Sorry for insisting on this question, but _why_ cannot the instance
> be considered as complete ? Well, the generic body could depend on an
> uncompletely defined type, hence the instance too. But the instance
> could also be clearly complete, couldn't it ? In my code, it is!
> In that case what does the "renames" bring ? Is it purely formal
> or does it reflect some indirections (indirect access to the procedure) ?

I only believe that I know the answer to the last question.  Some
indirection _is_ (/can be?) involved.  The kind of type conformance
called "subtype conformance" is related to "renaming as body".  It lets
the renaming as body be implemented by a compiler as a simple jump
instruction.  I read this description in section 6.2 on page 6-4 of the
Ada 95 Rationale.   

> 
> NB: I have seen in the Manual many topics about completion (3.10.1, 3.11.1,
> 7.6.1, 9.5.2) and the one that seems the most relevant here, 8.5.4(5) but

The Rationale section that I mentioned also refers to the RM Section on
Conformance rules (RM95 6.3.1). 

> I didn't guess the motivations behind these rules...
> Maybe some wise one knows them or can decipher the Runes ? ;-)

Yes, I do not know the underlying reasons, I just remembered from
reading the RM.

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> Gautier  --  http://members.xoom.com/gdemont/gsoft.htm