[Interest] App crashing because of ImageProvider when exiting

[Nuno Santos]

Hey folks,

I was misunderstanding the concept of heap and stack variables. I have made:

engine.addImageProvider("pictures", new ImageProvider());

The problem is now solved!

Thanks for your help!

Regards,

Nuno

> On 25 Jul 2018, at 12:35, 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 <mailto: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 <mailto: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 <mailto: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/> <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> <mailto:nunosantos at imaginando.pt <mailto: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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