Re: An alternative to Unchecked Conversion

[Simon Wright <simon@pogner.demon.co.uk>]

Brian Orpin <abuse@borpin.co.uk> writes:

> Well the Tartan Ada (83) compiler we are using doesn't allow us to use
> address mapping as it requires all address statements to be static.
> 
> With SYSTEM;
> Use SYSTEM;
> 
>   Procedure TEST Is
>      Type TEST_TYPE Is New INTEGER;
>      For TEST_TYPE'Size Use 32;
> 
>      X : TEST_TYPE;
>      Y : TEST_TYPE;
>      For X Use At Y'Address;
> 
>   Begin
> 
>      X := 1;
> 
>   End TEST;
> 
>    9|     Y : TEST_TYPE;
> test.ada:10:1:
>   10|     For X Use At Y'Address;
>                         ^1
> ***  1 Error 3271: A static expression is expected here (RM83 4.9)

I was expecting GNAT to complain similarly about this but neither
3.11p nor 3.12a2 does, so clearly I haven't understood.

Under similar circumstances, the typical solution is like

     X : TEST_TYPE;
     Y : TEST_TYPE;
     Y_Address : constant Address := Y'Address;
     For X'Address  Use Y_Address;

(Brian, are you still using 83? because "For X Use At Y'Address" is an
83-ism)