Re: How to Emulate C++ Macro with Static Local Variable?

["Robert I. Eachus" <rieachus@attbi.com>]

Randy Brukardt wrote:

> That's the idea behind AI-282. As I recall, we decided we didn't like the
> original proposal, but Bob and Tuck had a better idea. (Which we're still
> waiting for.)

I rechecked, and what we are talking about here is not provided in 
AI-282.  I probably want to think about it some more, but it would be a 
tremendous debugging aid without much cost.  This particular attribute 
would be the address from which the current instance of the enclosing 
procedure is called:  Some_Program'Call_Address.  Thinking about it, 
might as well make it the return address.  That is what is on the stack 
and is always very easy to get.  (I would advocate that the attribute 
should only be usable within the direct scope of the the named 
procedure.  (In other words, we don't want to favor implementations with 
static links.  Or maybe both static link and display implementations can 
do it fairly easily.)

The real use for this is where a subroutine has to do "extra" checking 
when it is called from user code instead of OS code.   It also makes 
writing some OS utilities marginally easier.

-- 
                                     Robert I. Eachus

Ryan gunned down the last of his third white wine and told himself it 
would all be over in a few minutes.  One thing he'd learned from 
Operation Beatrix: This field work wasn't for him. --from Red Rabbit by 
Tom Clancy.