D7870: Don't crash if a client (legally) uses a deleted global

[Anthony Fieroni]

anthonyfieroni added inline comments.

INLINE COMMENTS

> blur_interface.cpp:49
>      static Private *cast(wl_resource *r) {
> -        return reinterpret_cast<Private*>(wl_resource_get_user_data(r));
> +        auto blurManager = reinterpret_cast<QPointer<BlurManagerInterface>*>(wl_resource_get_user_data(r))->data();
> +        if (blurManager) {

QPointer itself can determine that resource is deleted but QPointer* acts like every normal pointer e.g. it can be dangling. So if unbind is called before cast this line will crash.

> blur_interface.cpp:89
>  {
> -    Q_UNUSED(resource)
> -    // TODO: implement?
> +    delete reinterpret_cast<QPointer<BlurManagerInterface>*>(wl_resource_get_user_data(r));
>  }

To work your idea this line should be

  delete reinterpret_cast<QPointer<BlurManagerInterface>*>(wl_resource_get_user_data(r))->data()

QPointer *should* live to not be dangling in cast, so you can have a static map resource to QPointer* then you can update and delete them at server die.

REPOSITORY
  R127 KWayland

REVISION DETAIL
  https://phabricator.kde.org/D7870

To: davidedmundson, #plasma
Cc: anthonyfieroni, plasma-devel, #frameworks, ZrenBot, progwolff, lesliezhai, ali-mohamed, jensreuterberg, abetts, sebas, apol, mart
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