[fpc-devel] Optimization breaks check for overridden function / Is there a better way to check?

[Sven Barth]

Sven Barth <pascaldragon at googlemail.com> schrieb am Mo., 20. Okt. 2025,
22:14:

> Am 18.10.2025 um 22:39 schrieb Bart via fpc-devel:
>
> On Fri, Oct 17, 2025 at 9:33 PM Sven Barth via fpc-devel<fpc-devel at lists.freepascal.org> <fpc-devel at lists.freepascal.org> wrote:
>
>
> David's problem is *not* due to a corruction or a bug, but due to an
> optimization that FPC performs that leads to different behavior, namely
> changing virtual methods that are empty to EmptyMethod to reduce the
> number of duplicate (empty) methods in the binary.
>
> Does that mena that such a check is in essence invalid?
> IIRC then we have such a check in TCustomEdit in LCL....
>
> Well, the language does neither explicitly forbid nor allow it... So you'd
> have to do a more complete check that includes both the real base method as
> well as System.EmptyMethod. Maybe best move the general check to a separate
> function which gets passed both method pointers and then compares those as
> well as the base one against EmptyMethod.
>

Sleeping about this a bit I think the solution needs to if either of two
methods is redirected to EmptyMethod then the code must assume that the
method was overridden, cause that's the only save assumption it can do (and
afterall code should handle that gracefully even if it might be less
optimal from the developer's point of view).

Regards,
Sven

>
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