@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.

@jsulm Yep, absolutely, there is much to read/fiddle with, and may not be portable. May or may not work for OP's particular case. Anyway, whether this or your core dump suggestion (OP should look up how his target Linux OS handles core dumps allowed or not), he has a few approaches to consider now....

Hi, Not the same backend used. Unless you re-build Qt and force the use of OpenSSL. Qt on macOS uses Apple's SecureTransport framework. OpenSSL on that platform has been deprecated a long time ago.

@sykac said in Turning off power to a running QSerialPort: One problem starts probably in the hardware. The COM port of the device disconnects from the PC (I don't why, it could be some driver/firmware issue) Reading you topic title, could it be that the USB connection between PC and FTDI is interrupted? And that's what I said, this may lead to endless loops in the device driver. This kind of problems can hardly be solved in the user space.

@nwoki Hi It means even it reports thats its QtWidgets that crashes, its likely not that DLL if a plain empty GUI project works. ( for exact same folder , same pc) I would next add some openGL to the test project see if it still runs. As it seems might be direclt related to Qt ( like wrong Qt dll loaded) so it could be the openGL for clients gfx card.

@Konstantin-Tokarev The problem has been solved. I change the float strategy from neon to vfpv3 and everything works well.

@sierdzio said in Segfault core dumped: Anyway, the bug is in line 61 in = &inFile; - you assign a variable created on a stack to variable in. In the next line, the inFile goes out of scope and is deleted. So when you try to access in later in the code, it segfaults. Thanks !! . I know it's not Qt problem but that's why i posted it in C++ section

Hi @jsulm and @Paul-Colby, if (segs) { delete[] segs; segs = nullptr; } This is an anti-pattern! Just make sure segs is nullptr before you call new and set it to nullptr after delete. No need to check for nullptr before delete: delete segs; segs = nullptr; Quoting the C++ Reference: "If this is a null-pointer, the function does nothing." Regards

In the PyQt 4.9.4 code downoaded from https://sourceforge.net/projects/pyqt/files/PyQt4/ I find (Note that we are using 4.9.3 but I couldn't find the sources of that version) void sipQLineEdit::changeEvent(QEvent *a0) { sip_gilstate_t sipGILState; PyObject *sipMeth; sipMeth = sipIsPyMethod(&sipGILState,&sipPyMethods[14],sipPySelf,NULL,sipName_changeEvent); if (!sipMeth) { QLineEdit::changeEvent(a0); return; } typedef void (*sipVH_QtCore_17)(sip_gilstate_t,PyObject *,QEvent *); ((sipVH_QtCore_17)(sipModuleAPI_QtGui_QtCore->em_virthandlers[17]))(sipGILState,sipMeth,a0); }

@dheerendra oh, I found where was the problem, and it wasn't actually related to context menus. I use my own BrowserApp class that inherits QApplication but I found out that I inherited it the wrong way (constructor signature was wrong) and that caused some segfaults, including the one described in my question. So now I fixed that and everything works fine.

@Wieland somehow It's still not working. The reason why I have to call initialize() inside the copyConstructor is, that you can't copy QOpenGLVertexArrayObject..

Thanks @SGaist !! . I will work on to improve it !!

@jsulm thanks I fixed it now. It was a stupid mistake, not setting up the static variable.

It is not the iterator that is the problem. From your example: for ( QList<QListWidgetItem*>::iterator iter = selectedItems().begin(); iter != selectedItems().end(); iter++ ) { qDebug() << (*iter)->text(); } The functions 'selectedItems().begin()' and 'selectedItems().end()' are the problem. Each time you call 'selectedItems()' a copy of QList<QListWidgetItem*> array is returned. Since you call it twice you have two different copies. The contents of the list may be the same but they are two different lists. Consider this: QString input_text(" some text for input "); QString text = input_text.simplified().trimmed().mid(1); In order to have the second line work a QString is constructed (and destroyed) for each step as a copy constructor. The QString member 'simplfied()' returns an unnamed instance of a new copy of QString after performing whatever 'simplfied()' does. The member 'trimmed()' is then called from this new QString creating another unnamed instance which finally calls member 'mid(1)'. The final variable 'text' is assigned from the last member function of the unnamed instance of QString. If the last member was '.toInt()' it would return an integer instead (which won't compile unless the assigned variable is changed to an integer (or acceptes an integer as a constructor)). The output from the above example is "ome text for input" if you are curious. The member function QListWidget::selectedItems(void) might looks something like this: QList<QListWidgetItem*> QListWidget::selectedItems(void) const { QList<QListWidgetItem*> list; list.push_back(<figure out what is selected>); return list; } You end up calling this function twice and therefore you have two different lists as you would expect (returned values from the same function will each have a unique instance). Your loop starts on the beginning of the first list and ends on the last item of the second list. It is very likely they are not sitting next to each other in memory so after the first list is traversed you are running over unknown memory (which is where your segfault comes from). You need to be careful about copy constructors (when they are created). For example, your 'for' loop uses the postfix operator 'iter++'. For simple variables (integers) this is not a problem but if you have a complex iterator calling the postfix version will be expensive at it creates a copy. A better form is to use the prefix operator '++iter' as no copy is created.

Good catch ! Since you have found the reason, please mark the thread as solved using the "Topic Tool" button so other forum users may know as solution has been found :)

I know, I too hate when people propose an alternative instead of answering the actual question but please forgive me this time. QXlsxWriter is a Qt based library to read and write excel files and I did not have many problems with it so far

How are you deleting your objects? Are you using delete or deleteLater? Seems odd this is happening since any delete on an object will delete all it's children before itself. At least with Qt parenting. If object X isn't a true child of B then that would cause your issue. I.e. if I have: QLabel *label = new QLabel(); QLabel *child = new QLabel(label); delete label; // label should delete child by before it fully deconstructs. Also if you have real code or at the very least a backtrace I could help more.