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Details

Type: Bug
Resolution: Done
Priority: P2: Important
Fix Version/s: 5.15.3, 5.15.7, 6.2.0 Beta4, 6.3.0 Alpha
Affects Version/s: 5.15.0
Component/s: GUI: Painting
Labels:
None
Environment:
Compiler: g++ 9.3.0
Operating system: Linux (Ubuntu 20.04)
Qt: 5.15.0 (downloaded from Qt)

Platform/s:

All
Commits:
47ded88e0c2f489e112b72f62151123db5c04dbe (qt/qtdeclarative/dev) 2812a7bf5699d0e1fe6c2c9dae2915acfd3da791 (qt/tqtc-qtquickcontrols2/5.15) 0437dbfc8811ccd44128ef6b413d933930a98114 (qt/qtdeclarative/6.2)

Description

There appears to be a memory leak when loading an icon by name. This can be demonstrated with a simple program that alternates the icon on a button. This was detected because we do an ASAN compile during development. It leaks about 150 bytes per icon, but this will quickly add up when you consider ListViews with ItemDelegates that have an icon on them, especially as they potentially reload when you scroll up and down the list.

QML:

Item {
  property int d_count: 1
		
  Timer {
    interval: 10
    repeat: true
    running: true

    onTriggered: ++d_count
  }

  CON2.ToolButton {
    anchors.centerIn: parent
    icon.name: (d_count % 2) == 0
      ? "edit-select-symbolic"
      : "error-correct-symbolic"
  }
	
  Component.onDestruction: {
    console.log("count=" + d_count)
  }
}

main.cpp (probably not too relevant)

//----------------------------------------------------------------------//
int main(int argc, char** argv)
{
  QCoreApplication::addLibraryPath("./3rdparty/qt5/plugins");

  QApplication app(argc, argv);	

  QQmlApplicationEngine engine;
  engine.addImportPath("qrc:///");
  engine.addImportPath("./3rdparty/qt5/qml");
  engine.load(QUrl("qrc:/APP_TEST_SQML/app_test_sqml_application.qml"));
  QApplication::exec();
  return 0;
}

The output of an ASAN build:

[matthewf-dev4 trunk]$ ./qml_simpletestprog 
qml: count=120

=================================================================
==1322176==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 5760 byte(s) in 120 object(s) allocated from:
    #0 0x56296331e167 in operator new(unsigned long) (/.../qml_simpletestprog+0x14a167)
    #1 0x7f5794f898d1 in QIconLoader::findIconHelper(QString const&, QString const&, QStringList&) const (/.../sharedlib/libQt5Gui.so.5+0x2038d1)

Indirect leak of 30836 byte(s) in 122 object(s) allocated from:
    #0 0x56296331c3e8 in __interceptor_malloc (/.../qml_simpletestprog+0x1483e8)
    #1 0x7f5795ce1f3c in QArrayData::allocate(unsigned long, unsigned long, unsigned long, QFlags<QArrayData::AllocationOption>) (/.../libQt5Core.so.5+0xbff3c)

SUMMARY: AddressSanitizer: 36596 byte(s) leaked in 242 allocation(s).

The leaks are proportional to the number of times the icon is alternated. To check this was not a false positive I ran a non-ASAN build and watched the memory usage with 'top' and it just kept climbing.

The problem allocations are in QIconLoader::findIconHelper