On Friday, 17 July 2020 09:56:39 PDT Giuseppe D'Angelo via Development wrote: > Il 17/07/20 17:30, Thiago Macieira ha scritto: > > I will give a +2 for this patch, since I prefer it. That means adding > > properties doesn't imply an extra 8 bytes per class in the hierarchy. > > Imagine a user class hierarcy like QSctpSocket -> QTcpSocket -> > > QAbstractSocket -> QIODevice -> QObject. If each class has properties, > > that adds 40 bytes to the full size of QSctpSocket. > > > > [Yes, I know Qt-based classes should just put their properties in the d > > pointer, but users don't usually have d pointers] > > Even with d pointers, how is that supposed to work? You still need the > dummy "property object" in the class where it's declared, right? That > would still add 1 byte to the class, although that can be folded into > the alignment. > > What am I missing here?
You're not, I was. You're correct, we still need the 1 byte structure added to the class. > So in your example QSctpSocket would still be 24 bytes, because the > inheritance is not deep enough to make sizeof 32? Yes, with the IA-64 ABI, assuming we don't mandate [[no_unique_address]] of course. With MSVC, it's 56 bytes. -- Thiago Macieira - thiago.macieira (AT) intel.com Software Architect - Intel System Software Products _______________________________________________ Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development
