Re: I'm facing an issue with: call to abstract procedure must be dispatching

[Serge Robyns <serge.robyns@gmail.com>]

On Thursday, 10 December 2015 00:03:15 UTC+1, Randy Brukardt  wrote:

> On top of which, it tends to limit how the client can use your package. In 
> particular, the client most likely couldn't put values of your object type 
> into a container, because Ada puts very strict limits on getting an access 
> value into a container. (Additionally, because of the extra runtime 
> accessibility checking, the access version is slower. That effect is small 
> enough that it shouldn't be a major determining factor in deciding which to 
> use, but if all other things are equal, why would anyone want to use the 
> slower version??)
> 
>                                          Randy.

This is an interesting topic.  I've always been wondering when the compiler is generating checks and when it does know he can skip them.  And what kind of test is the compiler doing on an access value.  Especially coming from the C world this is very "counter intuitive" :-P.

If the variable is as following:
  A_Reference : access not null T_something;  -- whereas T_Something is just a plain record type, i.e. not a tagged one.
and the procedure signature
  procedure Do_Something (Reference : not null access T_Something; ....);
What would happen with:
  Do_Something (A_Reference, ...);

My assumption is that the not null checks can be skipped during the call and inside the procedure.  What other checks are performed inside Do_Something for A_Reference?

Regards,
Serge