Both Asan and Valgrind show memory leak in QScroller::grabGesture(QObject*, QScroller::ScrollerGestureType)

[JoeCFD]

From valgrind:
==2274392== at 0x4849013: operator new(unsigned long) (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==2274392== by 0x61D8469: QScroller::grabGesture(QObject*, QScroller::ScrollerGestureType) (in /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5.15.3)

From Asan
#0 0x7f6f39cc81e7 in operator new(unsigned long) ../../../../src/libsanitizer/asan/asan_new_delete.cpp:99
#1 0x7f6f2f2b6413 in QScroller::grabGesture(QObject*, QScroller::ScrollerGestureType) (/lib/x86_64-linux-gnu/libQt5Widgets.so.5+0x512413)

Had a look at the source of QScroller and could not see the leak.
https://codebrowser.dev/qt5/qtbase/src/widgets/util/qscroller.cpp.html

And calling QScroller::ungrabGesture( QObject*) does not help.

Qt 5.15.3 and Ubuntu 22.04

[JoeCFD]

@JoeCFD created a bug report here and see if qt folks can confirm that there is some leak.
https://bugreports.qt.io/browse/QTBUG-124875

[kshegunov]

Are you certain it's not a false positive? As far as I hear valgrind really chokes on the QObject ownership (i.e. the object trees).

[JoeCFD]

@kshegunov I do know valgrind leak report may not be correct sometimes. I have one case in my app. But I am not sure about this one. Let Qt guys confirm the issue.

[Christian Ehrlicher]

@JoeCFD At least you should try it with Qt6.7 - I doubt someone will take a look on such things for an old Qt version just to see it's not there with recent Qt head.

[JoeCFD]

@Christian-Ehrlicher Good point. Busy with a release and no time to check it out. The bug report has been marked as Critical by Qt guys.