[Interest] App crashing because of ImageProvider when exiting

[Jean-Michaël Celerier]

you still have a double delete in this case. A first delete when
QQmlApplicationEngine is destroyed at the end of the main, and a second
delete when the static is deleted.



-------
Jean-Michaël Celerier
http://www.jcelerier.name

On Wed, Jul 25, 2018 at 1:35 PM, Nuno Santos <nunosantos at imaginando.pt>
wrote:

> Sérgio,
>
> Thanks for your reply.
>
> I have tried the following:
>
> *ImageProvider imageProvider;*
>
> *int main(int argc, char *argv[])*
> *{*
> *    QGuiApplication app(argc, argv);*
>
> *    Controller controller;*
>
> *    QQmlApplicationEngine engine;*
>
> *    engine.rootContext()->setContextProperty("controller", &controller);*
> *    engine.load(QUrl(QStringLiteral("qrc:/qml/main.qml")));*
> *    engine.addImageProvider("pictures", &imageProvider);*
>
> *    return app.exec();*
> *}*
>
> No success, still crashing at exit.
>
> malloc: *** error for object 0x10b69efd8: pointer being freed was not
> allocated
> *** set a breakpoint in malloc_error_break to debug
>
> The crash goes away if I comment *engine.addImageProvider("pictures",
> &imageProvider);*
>
> What am I missing here?
>
> Thanks!
>
> Nuno
>
> On 25 Jul 2018, at 12:20, Sérgio Martins <sergio.martins at kdab.com> wrote:
>
> Hi Nuno,
>
>
> The docs for QQmlEngine::addImageProvider() say: "The QQmlEngine takes
> ownership of provider".
>
> So QQmlEngine::removeImageProvider() is calling free() on stack variable,
> hence it complains that address wasn't heap allocated.
>
> Create it on the heap as suggested by Jean-Michaël.
>
>
> Regards,
> --
> Sérgio Martins | sergio.martins at kdab.com | Senior Software Engineer
> Klarälvdalens Datakonsult AB, a KDAB Group company
> Tel: Sweden (HQ) +46-563-540090, USA +1-866-777-KDAB(5322)
> KDAB - The Qt, C++ and OpenGL Experts
>
>
>
> On 2018-07-25 11:59, Nuno Santos wrote:
>
> Jean,
> This is the main context. It will not get out until app.exec() terminates.
> That’s why I’m connecting to aboutToQuit signal in order to remove the
> provider from the Qml engine.
> I had the provider instantiated inside the controller but I was having
> this problem already, therefore my efforts in getting it fixed.
> QQmlApplicationEngine *e;
> int main(int argc, char *argv[])
> {
>    QGuiApplication app(argc, argv);
>    Controller controller;
>    QQmlApplicationEngine engine;
>    e = &engine;
>    engine.rootContext()->setContextProperty("controller", &controller);
>    engine.load(QUrl(QStringLiteral("qrc:/qml/main.qml")));
>    ImageProvider imageProvider;
>    engine.addImageProvider("pictures", &imageProvider);
>    QObject::connect(&app, &QGuiApplication::aboutToQuit, [=]()
>    {
>        e->removeImageProvider("pictures");
>    });
>    return app.exec();
> }
> Any ideas?
> Regards,
> Nuno
>
> On 25 Jul 2018, at 11:30, Jean-Michaël Celerier <
> jeanmichael.celerier at gmail.com> wrote:
> Shouldn't you allocate your ImageProvider on the heap or at least ensure
> that it survives during the whole execution ? here it will be deleted by
> the end of your function
> -------
> Jean-Michaël Celerier
> http://www.jcelerier.name <http://www.jcelerier.name/>
> On Wed, Jul 25, 2018 at 11:24 AM, Nuno Santos <nunosantos at imaginando.pt <
> mailto:nunosantos at imaginando.pt <nunosantos at imaginando.pt>>> wrote:
> Hi,
> Yesterday I have used for the first time a QQuickImageProvider but I’m
> having problems because now the app crashes when I terminate it.
> Tried to do the following in order to avoid the crash but it is crashing
> anyway:
> ImageProvider imageProvider;
> engine.addImageProvider("pictures", &imageProvider);
> QObject::connect(&app, &QGuiApplication::aboutToQuit, [=]()
> {
>    e->removeImageProvider("pictures");
> });
> The crash is always something like this:
> malloc: *** error for object 0x7ffeef34e900: pointer being freed was not
> allocated
> Does anyone knows how to fix this?
> Thanks!
>
>
>
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