Il 16/07/20 12:43, Volker Hilsheimer ha scritto:
For pre-C++20 (where it’s possible to have zero-size structs), and for 
compilers that don’t respect the [[no_unqiue_address]] attribute, all these 
struct-instances are put into a union. In that case, a class using QProperty 
will be larger (by the same amount no matter the number of properties) than the 
same class in Qt 5. With C+++ 20 and compilers that do respect 
[[no_unique_address]], the size and layout of these classes will be the same.

I'm not fully understanding this last part -- does changing compiler break ABI, because the implementation of properties change (from an union to [[no_unique_address]] members)?

Thanks,

--
Giuseppe D'Angelo | giuseppe.dang...@kdab.com | Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com
KDAB - The Qt, C++ and OpenGL Experts

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