[fpc-devel]Re: Freepascal bug?

[Balogh, Karoly (Charlie/iNQ)]

Hi,

On 03.10.13., Tamas Konkoly wrote:

> I would like to know why don't work the first d declaration.
> The second declaration work only well, because I checked it.
> 
> type TR=record
>       a,b,c:longint;
>     end;
> var data:array[0..100]of TR;
> procedure pp(var r:TR);
> var d:^TR;
> begin
> d:=@r[20]; // << this is not compileable
> d:=@r+20*sizeof(TR); // << this is compileable
> end;
> 
> begin
> pp(data[0]);
> end.

This code is buggy, and shows bad coding too, IMO. The problem is
that r is not an array. The easiest way to fix is some typecasts.

type PTR = ^TR;

d:=@(PTR(@r)[20]); // ugly;

IMO, the above code should look like this:

type PTR=^TTR;
     TTR=record
       a,b,c:longint;
     end;
var data:array[0..100] of TTR;
procedure pp(r:PTR);
var d:PTR;
begin
 d:=@r[20];
end;

begin
pp(@data[0]);
end.

Hope this helps. 
You can ask me in private mail in hungarian if needed.

Bye,
-- 
Charlie/iNQ      (SceneCON - http://scenecon.intro.hu)
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