[fpc-pascal] Variant record consistency

[Gerhard Scholz]

I assume, my response was a bit unclear. If you code it like this, you 
should get a runtime-error or compiler-error if the two variants are not 
same-sized, and I assume, this is what you wanted.

----- Original Message ----- 
From: "Gerhard Scholz" <gs at g--s.de>
To: "FPC-Pascal users discussions" <fpc-pascal at lists.freepascal.org>
Sent: Sunday, August 07, 2016 8:00 PM
Subject: Re: [fpc-pascal] Variant record consistency


> 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]
>> _______________________________________________
>> fpc-pascal maillist  -  fpc-pascal at lists.freepascal.org
>> http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
>
> _______________________________________________
> fpc-pascal maillist  -  fpc-pascal at lists.freepascal.org
> http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal