Re: [fpc-pascal] Pointer question

[Sven Barth via fpc-pascal]

Hairy Pixels via fpc-pascal  schrieb am
Mi., 9. Aug. 2023, 04:59:

> I just noticed this by accident and I don't understand. Why does " x :=
> @r; " compile? I would expect it to fail like the next line where I cast to
> the explicit type.
>
> type
>   TMyRec = record end;
>   PMyRec = ^TMyRec;
> var
>   x: PByte;
>   r: TMyRec;
> begin
>   x := @r;// works
>   x := PMyRec(@r);  // fails
> end.


By default @ returns a *untyped* pointer that can be assigned to any
pointer type. Thus is compatible with Delphi and can be controlled with the
$TypedAddress directive (there's a slight exception to this when you assign
a pointer to a function to a function variable (etc) or pass it to such a
parameter, because the compiler has to pick the correct overload if there
are multiple functions with the same name in scope).

Regards,
Sven

>
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[fpc-pascal] Pointer question

[Hairy Pixels via fpc-pascal]

I just noticed this by accident and I don't understand. Why does " x := @r; " 
compile? I would expect it to fail like the next line where I cast to the 
explicit type.

type
  TMyRec = record end;
  PMyRec = ^TMyRec;
var
  x: PByte;
  r: TMyRec;
begin
  x := @r;// works
  x := PMyRec(@r);  // fails
end

Regards,
Ryan Joseph

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