Application crashes while accessing Pointers and while Hovering over custom QGraphicsItems

Lanparty

Hi there! Thank you so much.

The crash currently happens when I start the application (i think due to ellipse1->checkPointers();) or when I hover over one of the circles with my cursor.

mrjj

@Lanparty
Hi
So if you put break point at
void Slice::hoverEnterEvent(QGraphicsSceneHoverEvent *)
and single step over the code.
Can you then pinpoint which line it does crash in?

Lanparty

@mrjj Hey, if i put the breakpoint where you implied it does not even get to the breakpoint and I only get the segfault (see above in screenshot) again.

Even after commenting // ellipse1->checkPointers(); out it still behaves the same way while debugging.

However when starting the application it starts now without crashing immediately (after taking out / ellipse1->checkPointers();), it only crashes once I hover over the objects.

But I'll try to find the position where it crashes and I'll update this message or post another reply once I know.

mrjj

@Lanparty
Ok so its before hoverEnterEvent. thats odd.
Also, there really is nothing of your code in call stack ?

SGaist

Hi,

The stack trace you posted seems to be from a release build. Can you share the stack trace from your debug build ?

Lanparty

@mrjj @SGaist

Hi! Thanks again for your replies and your interest in my current problem.
I'm not quite sure if I did this the correct way, but I think I figured out how to get what you asked and I hope that this information is what you've been looking for.

This should be the call stack from my debug build (at least I hope it is :'D):

1  ntdll!RtlGetCurrentServiceSessionId                                                   0x77ae4cd9 
2  ??                                                                                    0xb80afd3f 
3  ??                                                                                    0x1ef069b0 
4  ntdll!RtlFreeHeap                                                                     0x77ae3812 
5  ntdll!RtlpNtSetValueKey                                                               0x77b82ea1 
6  ntdll!RtlGetCurrentServiceSessionId                                                   0x77ae3c45 
7  ??                                                                                    0x1ef069b8 
8  ntdll!RtlFreeHeap                                                                     0x77ae3812 
9  msvcrt!free                                                                           0x76a070b5 
10 ??                                                                                    0x1f0000   
11 QWindowsFontDatabase::releaseHandle                     qwindowsfontdatabase.cpp 1601 0x62a928b6 
12 QtFontStyle::~QtFontStyle                               qfontdatabase.cpp        234  0x1372329  
13 QtFontFoundry::~QtFontFoundry                           qfontdatabase.cpp        303  0x138530c  
14 QtFontFamily::~QtFontFamily                             qfontdatabase.cpp        365  0x1375138  
15 QFontDatabasePrivate::free                              qfontdatabase.cpp        482  0x13a8915  
16 QFontDatabasePrivate::~QFontDatabasePrivate             qfontdatabase.cpp        470  0x13a89af  
17 (anonymous namespace)::Q_QGS_privateDb::Holder::~Holder qfontdatabase.cpp        720  0x1121bed  
18 __tcf_0                                                 qfontdatabase.cpp        720  0x1121c0a  
19 _CRT_INIT *12                                                                         0x10511b4  
20 __DllMainCRTStartup                                                                   0x1051325  
21 DllMainCRTStartup *12                                                                 0x1051433  
22 ntdll!RtlCheckTokenCapability                                                         0x77b0a896 
23 ntdll!RtlHashUnicodeString                                                            0x77ae01a6 
24 ntdll!LdrShutdownProcess                                                              0x77ad458d 
25 ??

I hope this helps. Enjoy your weekend and thanks again!

mrjj

@Lanparty
Hi
Super.
Is that from when it crashes ?

Lanparty

@mrjj yeah, well I ran the debugger and this is what happened afterwards (including the application crashing)

Lanparty

@Lanparty said in Application crashes while accessing Pointers and while Hovering over custom QGraphicsItems:

void Slice::hoverEnterEvent(QGraphicsSceneHoverEvent *)
{
    if (text.isNull())
        return;

    QString percentageAsString = QString::number(int(this->getPercentage()));

    text.data()->setPlainText(this->category + " " + percentageAsString + "% ");

    int xOffset = int(rect().x() + rect().width()/2);
    int yOffset = int(rect().y() + rect().height()/2);

    QPointF newCenterPoint = QPointF(this->pos().x()+ xOffset, this->pos().y() + yOffset);
    QPointF textPoint = newCenterPoint;

    textPoint.setX(this->x() + 100);

    text.data()->setPos(textPoint);

    text.data()->setVisible(true);
}

so, I actually managed to find out where my application crashed. The problem was this line:

 text.data()->setPlainText(this->category + " " + percentageAsString + "% ");

once I checked the expected parameters it kind of made sense. I'll try to find another way to achieve the string I originally wanted to be displayed.

SGaist

Do you mean you were missing the text.isNull() check ?

Lanparty

@SGaist No, that's the first thing I did inside the method. However, I simply assumed that I could use the method setPlainText() as I pleased, but it was expecting other arguments and crashed instead (I guess because the QString text would've been longer than the original one.

btw: how do I change the status of my post to "solved"?

mrjj

@Lanparty said in Application crashes while accessing Pointers and while Hovering over custom QGraphicsItems:

btw: how do I change the status of my post to "solved"?

First post, Topic Tools button to the side.