Strange crash with QPointers in a container

[aart]

I'm developping an application where instances of an abstract base class need to keep references to other instances of the same base class. I thought to use Qpointers for that to avoid any possible dangling pointers. But for some reason everything I try results in the application freezing and windows telling me the application is not responding.

This is where it goes wrong:

class SomeClass : public QObject{
Q_OBJECT
public: 
    ...
protected:
    QVector<QPointer<SomeClass>> test{ 3 }; 
}

I have tried multiple container classes: vector QVector QList , all of them result in the application freezing. I'm quite new to Qt. is THere something I'm doing wrong here? Am I making some mistake with my usage of QPointer?

Thanks in advance!

[aart]

It's even stranger than I thought:

having this is allowed:

    QPointer<BaseTOP> a;
    QPointer<BaseTOP> b;
    QPointer<BaseTOP> c;
    QPointer<BaseTOP> d;
    QPointer<BaseTOP> e;

But this is not:

std::array<QPointer<BaseTOP>, 4> test;

What is going on here?

[Pl45m4]

@aart

Hi,

when does it crash? Where do you initialize your class objects?

[aart]

@Pl45m4
I have a single threaded application, i create the objects in QGraphhicsView's mouseDoubleClickEvent function. Nothing strange i can think of ...

[Christian Ehrlicher]

Still no answer where exactly it is crashing and what's the code where it is crashing + backtrace....

[Pl45m4]

@aart said in Strange crash with QPointers in a container:

This is where it goes wrong:

class SomeClass : public QObject{
Q_OBJECT
public:
...
protected:
QVector<QPointer<SomeClass>> test{ 3 };
}

I dont think that this is the part of your code where it crashes :)
Where do you push the objects in your vector? Where do you try to access them / use the pointers?
Without any code, nobody can help you.

@aart said in Strange crash with QPointers in a container:

QVector<QPointer<SomeClass>> test{ 3 };

This doesnt look wrong (QVector, Lenght 3, with QPointers to SomeClass-object)

[aart]

@Christian-Ehrlicher The thing is that it doesnt actaully crash but just gets stuck and stops responding, I cant really post all the code here because that would be way too much. Is there any way i can get some sort of error log that people can get information out of?

[Christian Ehrlicher]

Use a debugger to see where it hangs. I don't see why it should 'hang' because of a pointer in a vector.

[mrjj]

Hi
I tried your SomeClass in a small project but nothing happened.
Im not really sure its related to QPointer as there is no reason why it should
do odd stuff. Code seems pretty normal.

Do you have s small sample that will produce the "odd part" ?

[aart]

@Christian-Ehrlicher
Okay so using the debugger i found where the problem lays. I'm very new to qt and qt creator, so i didnt understand how to use the debugger :p The issue was indeed not in the class with the vector but elsewhere in the code where i was using the data stored in the vector. Thanks for the help everyone. The thread can be closed.

[Christian Ehrlicher]

@aart said in Strange crash with QPointers in a container:

The thread can be closed.

This can be done by you by editing the first post and setting it to resolved. :)

[aha_1980]

@Christian-Ehrlicher said in Strange crash with QPointers in a container:

@aart said in Strange crash with QPointers in a container:

The thread can be closed.

This can be done by you by editing the first post and setting it to resolved. :)

No, just use the button Topic Tools. There is an entry Mark as Resolved.