MetaEngine::save() is re-implemented in DMetadata without to use virtual property.

[Gilles Caulier]

Hi Marcel,

Yes the code is valid, but so far wrong in the concept of oriented
objects programming.

I know the suggested override compiler method, and it's activated here.

Also all static analyzers must report this kind of overload method,
but nothing appears...

Best

Gilles

Le ven. 13 nov. 2020 à 17:41, Marcel Mathis <maeseee at gmail.com> a écrit :
>
> Hi Gilles
>
> This is completely valid code if the virtual is missing. So I don't think there is a compiler error or warning. See the attached example.
>
> I would advise to use the compiler flag -Werror=suggest-override. So you can guarantee that all overridden functions are at least virtual.
>
> Hope to help you with this information.
>
> Cheers
> Marcel
>
> On Fri, Nov 13, 2020 at 4:16 PM Gilles Caulier <caulier.gilles at gmail.com> wrote:
>>
>> A partial response can be found here :
>>
>> https://stackoverflow.com/questions/1853896/is-it-possible-to-override-a-non-virtual-method
>>
>> This is typically possible but highly not recommended and not portable
>> everywhere... as i understand...
>>
>> Gilles
>>
>> Le ven. 13 nov. 2020 à 16:11, Gilles Caulier
>>
>> <caulier.gilles at gmail.com> a écrit :
>> >
>> > And it's the same for MetaEngine::applyChanges() ....
>> >
>> > Gilles
>> >
>> > Le ven. 13 nov. 2020 à 16:10, Gilles Caulier
>> > <caulier.gilles at gmail.com> a écrit :
>> > >
>> > > Hi, all,
>> > >
>> > > I currently review all Clazy static analyzer reports, and i plan to
>> > > merge DMetadata class to MetaEngine.
>> > >
>> > > While reviewing the code I discovered that MetadaEngine::save() is
>> > > implemented into DMetadata without being declared as virtual.
>> > >
>> > > I'm surprised to not see a G++ warning about this code, which can
>> > > introduce side effects... Look by yourself :
>> > >
>> > > https://invent.kde.org/graphics/digikam/-/blob/master/core/libs/metadataengine/engine/metaengine.h#L372
>> > >
>> > > https://invent.kde.org/graphics/digikam/-/blob/master/core/libs/metadataengine/dmetadata/dmetadata.h#L95
>> > >
>> > > How is it technically possible ?
>> > >
>> > > Best
>> > >
>> > > Gilles Caulier