Re: Type System.ADDRESS

[emery@goldfinger.mitre.org (David Emery)]

>  Any assignments to type System.Address require a static expression.

This sounds like a compiler bug to me.  

First, the following is legal Ada, i.e. you can compute arbitrary
values of type System.address and assign them to variables of the
type: 
  
    X : system.address;
    A, B : integer;
  begin
    if (some_random_event) then
      X := A'address;
    else
      X := B'address;
    end if;
  end;
  
Let's now look at address representation clauses.   For instance,
given Address A, the address of an integer, the following is legal
Ada: 
  
  I : integer;
  for I use at A;

Ada83 (Ada87) RM, 13.5(2) says that the expression must be a
"simple_expression".  This is NOT the same as a
"static_simple_expression" (e.g. 13.4 (2), alignment_clause for a
record representation).  

Therefore the following is legal Ada (although potentially erroneous):
  
  with System;
  function I_at_addr (addr : System.address)
      return integer
  is
     the_object : integer;
     for the_object use at addr;
  begin
     return the_object;
  end;

				dave
--
--The preceeding opinions do not necessarily reflect the opinions of
--The MITRE Corporation or its sponsors. 
-- "A good plan violently executed -NOW- is better than a perfect plan
--  next week"                                      George Patton
-- "Any damn fool can write a plan.  It's the execution that gets you
--  all screwed up"                              James Hollingsworth
-------------------------------------------------------------------------