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  1. Qt
  2. QTBUG-138919

[Reg 6.5.9 -> 6.8.4] Unreferenced objects with JavaScriptOwnership are no longer destroyed

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    • b1c48db75 (dev), 6efdecd36 (6.10), 28cb8f65b (6.9)

      See the attached example. CppObj is a QML_ELEMENT while CppBridge is a QML_SINGLETON.

      It creates 3 CppObjs with JavaScriptOwnership and no parent:

      Identifier Comment
      -1 Instantiated declaratively in QML
      0 Instantiated from C++, not stored
      1 Instantiated from C++, stored in QML property

       

      Code

      import QtQuick
import QtQuick.Controls.Basic
import JSOwnershipStudy

Window {
    width: 400
    height: 300
    visible: true

    property CppObj objFromCpp: CppBridge.singleObj(1) // identifier == 1
    CppObj { id: objFromQml } // identifier == -1

    Component.onCompleted: {
        const orphanedObj = CppBridge.singleObj(0) // identifier == 0
    }

    Button {
        text: "Collect Garbage"
        onClicked: gc()
    }
}

       

      Steps to reproduce

      1. Run the attached example
      2. Click the "Collect Garbage" button
      3. Close the window to quit

       

      Outcomes

      • (All versions) CppObj IDs -1 and 1 are destroyed upon quitting (Expected)
      • (Qt 6.5) CppObj ID 0 is destroyed by the garbage collector (Expected)
      • (Qt 6.8+) CppObj ID 0 is never destroyed (Not Expected)

       
      Setting QV4_GC_TIMELIMIT=0 and QV4_MM_AGGRESSIVE_GC=1 does not help.

        1. JSOwnershipStudy-SingleObjects.zip
          2 kB
        For Gerrit Dashboard: QTBUG-138919
        # Subject Branch Project Status CR V
        673208,2 QmlCompiler: Ensure QObjects returned to AOT-compiled code are wrapped tqtc/lts-6.8 qt/tqtc-qtdeclarative Status: NEW +2 0

            ulherman Ulf Hermann
            skoh-qt Sze Howe Koh
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              Created:
              Updated:
              Resolved: