binary compatibility and qwidget::event

[Harald Sitter]

That makes sense. Thanks all! :)

On Fri, Jul 12, 2019 at 1:09 PM Volker Krause <vkrause at kde.org> wrote:
>
> On Friday, 12 July 2019 11:24:35 CEST Harald Sitter wrote:
> > But why was that BIC to begin with? Which of the "don'ts" did it violate?
>
> IIUC re-implementing a virtual method from a base class (in absence of
> complications like multi-inheritance or co-variant return types) does not
> change the ABI (it changes vtable content, but not vtable layout).
>
> It does however create cases where old binaries still call the old methods
> (see https://community.kde.org/Policies/
> Binary_Compatibility_Issues_With_C%2B%2B#Adding_a_reimplemented_virtual_function).
> That might not always be a relevant problem though.
>
> In my understanding this is the same for the final -> !final case discussed in
> #plasma in this context. It does not impact the ABI at all (it does not even
> change vtable content), but some optimizations in old binaries might no longer
> reflect the new behavior.
>
> Regards,
> Volker
>
> > On Fri, Jul 12, 2019 at 11:18 AM Kai Uwe Broulik <kde at privat.broulik.de>
> wrote:
> > > To avoid situations like [1] and [2]
> > >
> > > [1]
> > > https://cgit.kde.org/kiconthemes.git/commit/?id=1e9af6c54470e890597739f8f2
> > > 189b0743a00b6f [2]
> > > https://cgit.kde.org/kiconthemes.git/commit/?id=083bb8a80fd5941e6fcbaf1ec1
> > > 2a08d8f8c881a5>
> > > Am 12.07.19 um 11:14 schrieb Harald Sitter:
> > > > Hey
> > > >
> > > > our binary compatibility page [1] states that one should
> > > >
> > > > "reimplement event in QObject-derived classes, even if the body for
> > > > the function is just calling the base class' implementation."
> > > >
> > > > Does anyone know the reason this helps maintain BC?
> > > >
> > > > [1]
> > > > https://community.kde.org/Policies/Binary_Compatibility_Issues_With_C%2
> > > > B%2B
> > > >
> > > > HS
>