Re: CONSTRAINT_ERROR - why?

[Jeffrey Carter <jrcarter@acm.org>]

Alfred Hilscher wrote:
> This program raises exception CONSTRAINT_ERROR for the second
> assignment. It happens with GNAT 3.13p and 3.14p (on windows).
> 
> Can someone explain why? Is this a compiler error or do I misunderstand
> something?

The reason Constraint_Error is raised is because the code violates a 
constraint.

Why are you using Interfaces.C if you're not interfacing with C?

Since the LHS of your assignment is type Byte, the expression is 
evaluated using

function "/" (Left, Right : Byte) return Byte;

The value passed to Left is not in the range of Byte. If you want this 
evaluated as a universal expression, you have to add a step:

declare
    Value : constant := X'Size / 8;
begin
    Y := Value;
end;

-- 
Jeff Carter
"Why don't you bore a hole in yourself and let the sap run out?"
Horse Feathers