[fpc-pascal] Variant record consistency

[Gerhard Scholz]

if same size is necessary, I would do it like this:

const
  topDataQword= 29;
  topNameChar= 231;

type
  Tfnord1 = array[0..topDataQword] of qword ;
  Tfnord2 = record
                       name: array[0..topNameChar] of char;
                       inode: qword
                     end ;
  Tfnord= record
             case boolean of
               false: (data: Tfnord1);
               true:  (ni : Tfnord2)
           end;

and, in the code:
  if sizeof(tfnord1) <> sizeof(tfnord2) then halt(4711);

or, in the data
type xxxxxxtest = array [ 1..ord(sizeof(tfnord1) = sizeof(tfnord2)) ] of 
boolean ;

----- Original Message ----- 
From: "Mark Morgan Lloyd" <markMLl.fpc-pascal at telemetry.co.uk>
To: <fpc-pascal at lists.freepascal.org>
Sent: Sunday, August 07, 2016 6:11 PM
Subject: [fpc-pascal] Variant record consistency


> Given a declaration
>
> const
>   topDataQword= 29;
>   topNameChar= 231;
>
> type
>   Tfnord= record
>             case boolean of
>               false: (data: array[0..topDataQword] of qword);
>               true:  (name: array[0..topNameChar] of char;
>                       inode: qword)     (* For recovery if name is changed 
> *)
>           end;
>
> is it possible to enforce a rule that the two record variants must be the 
> same size?
>
> -- 
> Mark Morgan Lloyd
> markMLl .AT. telemetry.co .DOT. uk
>
> [Opinions above are the author's, not those of his employers or 
> colleagues]
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