Re: Subprogram Pointer in a Generic

["Warren W. Gay VE3WWG" <ve3wwg@cogeco.ca>]

Samuel Tardieu wrote:
> Charles H. Sampson wrote:
>>     There are two questions.  (1) What are they trying to prevent by
>>this restriction?  (2) Is there a more robust way of working around it?
> 
> (1) The absence of such a rule would prevent an implementation from
>     implementing efficiently shared generic packages: if, from
>     within the body, you take a reference to a local subprogram,
>     you do not statically know the accessibility "depth", as the
>     generic package may be instantiated locally (from within a
>     subprogram for example).  Note that building the access value
>     from outside the generic package then storing it is subject to
>     the classical static accessibility rules and thus does not
>     require this restriction.
> 
> However, I must admit that I do not understand why it is not
> sufficient for the access to subprogram type to be declared in the
> corresponding generic declaration, as both accessibility levels can
> be statically compared when compiling the generic package body.
> 
> Should this restriction be alleviated in Ada 2005?

I think so. I found this to be a horrible limitation when it
was necessary to register a callback from within a generic.

-- 
Warren W. Gay VE3WWG
http://home.cogeco.ca/~ve3wwg