Re: Access parameters and accessibility

[sbelmont700@gmail.com]

> 
> Could someone give an example/explanation where this rule is used?
> I tried to read the RM. Chapter 3.10.2 seems to be the right one but I 
> don't understand it either...
> 

As others have pointed out, anonymous access types are 'expert friendly' at best, and there is a whole host of history and compromises as to why they are how they are, most of which are obsolete in 2012.  For 99% of situations, you don't have to lose any sleep over any of this (though I disagree with the 'never ever ever' attitude of others).

However, long story short, using an 'access parameter' (i.e. an anonymous access type as a subprogram parameter) requires passing along some meta-data about the object for various esoteric situations when a runtime check might be required.  However, as the author points out, there are some (even rarer) cases where what would normally require a runtime check would be statically known to be ok, and thus could be performed without risk.  That's all it's saying.

This is compiler detail, not a language rule, so I would doubt you would find it in the LRM (perhaps in the AARM, as a note?)  If you are a masochist, the same author produced a whitepaper back in the day going into much more gory detail about all this (ACM Ada Letters, Jan/Feb 1995, page 45 specifically).

-sb