Re: Is this definition legal?

["Björn Persson" <spam-away@nowhere.nil>]

Ludovic Brenta wrote:

> Whether or not your code is legal, a bug box is a bug.  I would be
> interested in a short test case for each of your issues (one for the
> bug box upon declaring a Character_Encoding without an initialiser;

That one is easy:

with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
with Interfaces; use Interfaces;

package Declaration_Bug_Box is

    type Known_OS is (NT, OS2, Linux);

    This_OS : constant Known_OS := Linux;

    type Encoding_ID is
      (UTF_8_ID, ASCII_ID, Latin_1_ID);

    type Unified_Encoding_Record (Known : Boolean; OS : Known_OS) is record
       case Known is
          when True =>
             Which : Encoding_ID;
          when False =>
             case OS is
                when Linux =>
                   Name : Unbounded_String;
                when NT | OS2 =>
                   Number : Unsigned_16;
             end case;
       end case;
    end record;

    type Character_Encoding (Known : Boolean := False) is
      new Unified_Encoding_Record (Known => Known, OS => This_OS);

    Trigger_Bug : Character_Encoding;

end Declaration_Bug_Box;

> one for the conversion that alters OS, and one where the conversions
> raises Constraint_Error.

Those are difficult to reproduce. I think they depend on uninitialized 
memory and I haven't quite figured out which constant, variable or 
parameter it is that doesn't get properly initialized. I'd need a way to 
reliably "pre-initialize" memory - that is, to make sure that the right 
kind of garbage is present before a variable or constant is created. I'm 
working on it.

-- 
Björn Persson                              PGP key A88682FD
                    omb jor ers @sv ge.
                    r o.b n.p son eri nu