[Qt-creator] Strange difference when running with debug, as opposed to just running

kai.koehne at nokia.com kai.koehne at nokia.com
Mon Jul 2 09:51:55 CEST 2012

The "Arrow with the bug in it" starts the application inside the Debugger. Unfortunately enabling QML debugging (checkbox in Run Settings of your project) breaks some Symbian components, so this is a known issue :( You can either decide to live with the effects, or disable QML debugging.

(The technical reason is that the QML Debugger in Qt 4.x runs it's own event loop inside the GUI event loop. This however can change the order of events being delivered to the application, which somehow breaks the components. This has been fixed in Qt 5.0 by moving the QML debugger into it's own thread, but that of course doesn't help for the Symbian case).

Hoe this helps,


PS: I'm not sure whether it makes a difference whether you let  your application run in the Simulator or on the device. 

From: qt-creator-bounces+kai.koehne=nokia.com at qt-project.org [qt-creator-bounces+kai.koehne=nokia.com at qt-project.org] on behalf of ext Harri Pasanen [harri at mpaja.com]
Sent: Thursday, June 28, 2012 5:54 PM
To: qt-creator at qt-project.org
Subject: [Qt-creator] Strange difference when running with debug,       as opposed to just running

I have some code that runs ok in Qt Simulator when launched from Qt
Creator  by clicking on the green arrow head.

But if I run it clicking the arrow head with a bug on it,  I see
messages like

Unable to assign QObject* to Popup_QMLTYPE_18*

TypeError: Result of expression 'containingPopup' [null] is not an object.

and when the application comes up, the toolbar (ToolBarLayout) is empty,
without any buttons.

Similarly, running with valgrind memcheck, the toolbar is populated ok,
and none of the above errors appear.

I'm not sure exactly at what moment this started happening, might have
been back when added the toolbar, as previous revision did not have
any.   I don't run the debugger so often, so I did not notice until now.

I don't have any breakpoints set.

Kind of strange, any ideas?


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