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  1. Qt
  2. QTBUG-104521

Missing move SMFs disable move semantics for QDom classes



    • Task
    • Resolution: Unresolved
    • P3: Somewhat important
    • None
    • 6.4.0 Beta1
    • XML: DOM
    • None


      The QDom classes have user-defined copy Special Member Functions (SMFs) and a user-defined destructor, which disables the implicit generation of move SMFs. These types are therefore not movable, in particular, they're not nothrow_move_{constructible,assignable}, so they perform more poorly than they could in many situations, such as returning from functions and reallocation of containers.

      Add move SMFs, possibly member-swap and free swap functions (by using Q_DECLARE_SHARED, if that's BC these days).

      Acceptance criteria:

      • All QDom value-like classes (incl. QDomNode hierarchy) have
        • an inline noexcept move constructor
        • an inline noexcept move-assignment operator
          • just swaps, not move-and-swap
        • an inline noexcept member-swap, if possible
          • probably need a way to prevent mixed-type swapping
            • see QPixmap/QBitmap for a technique
          • likely move-assignment needs the same protection
        • are marked as Q_DECLARE_SHARED, if possible
          • adding Q_D_S after release used to be BiC in Qt 5, check the situation in Qt 6, add Q_DECLARE_SHARED_NOT_RELOCATABLE_UNTIL_QT7 if Q_D_S is still a problem


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              cnn Qt Core & Network
              mmutz Marc Mutz
              Vladimir Minenko Vladimir Minenko
              Alex Blasche Alex Blasche
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