PyQT program crashes on Mac (not on Windows) when clicking on QComboBox

[guillermollopis]

I am using pyqt in python for a program with a QDialog and a QMainWindow. When the program starts, the QDialog is shown. Here the user can choose a file type with a QComboBox and there is a button to open the directory and choose a file. Once this is done, the QDialog is closed and the QMainWindow is shown. On the QMainWindow, there is an option to go back to the QDialog and choose another file.
All these things work perfectly, but a problem comes when I go back to the QDialog from the QMainWindow and I click on the QComboBox. The program is closed with an error of EXC_BAD_ACCESS and KERN_INVALID_ADDRESS. This just happens when I click on the QComboBox, not on any other widget in the screen. Also, this just happend when using Mac, with Windows I do not have any problem.
The code I use to open the QDialog is

def request_user_input_database_and_file(self):

        try: 
            app = QApplication(sys.argv)
            mainWindow = MyMainImport(self)
            mainWindow.show()
            if QApplication.instance():
                app.exec_()

            if self.continue_value == False:
                sys.exit(1)

            self.after_input()
        except:
            sys.exit(1)

The class that is referenced is

class MyMainImport(QDialog):
    
    def __init__(self, palms):
        super().__init__()
        
        self.initUI(palms=palms)

        # Get the desktop widget
        desktop = QApplication.desktop()

        # Get the screen height
        screen_height = desktop.screenGeometry().height()

        # Calculate the new height as 80% of the screen height
        new_height = int(screen_height * 0.8)

        self.setWindowIcon(QtGui.QIcon(str(ICON_PATH)))
        
        self.resize(850, new_height)  # Set the window size (width, height)
        self.move(QDesktopWidget().availableGeometry().center() - self.rect().center())  # Set the starting position of the window (x, y)

        # Set the fixed size of the window
        self.setFixedSize(850, new_height)
def initUI(self, palms):
        # central widget
        self.widget = ImportData()
        central_widget = QWidget()

        # create layout and add components
        self.lay = QVBoxLayout(central_widget)
        self.lay.addWidget(self.button)
        self.setLayout(self.lay)

        self.lay.addWidget(self.widget)

And the class with the combo box is

class ImportData(QWidget):
    
    def __init__(self, multiple=False):
        super().__init__()

        # Create the main vertical layout
        self.main_layout = QtWidgets.QVBoxLayout(self)

        # Create the scroll area
        scroll_area = QtWidgets.QScrollArea()
        scroll_area.setWidgetResizable(True)
        scroll_area.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        # Create the widget to hold the frames
        scroll_contents = QtWidgets.QWidget()
        self.layout = QFormLayout(scroll_contents)
        # Set the scroll area contents
        scroll_area.setWidget(scroll_contents)

        self.main_layout.addWidget(scroll_area)

        # Create the main selector layout
        selector_layout = QHBoxLayout()


        # Create and add the components for the first line
        selector_left_button = QPushButton("<")
        selector_left_button.setFixedHeight(20)
        selector_layout.addWidget(selector_left_button)

        self.currentSelector = 1
        self.selector_label = QLabel("File " + str(self.currentSelector))
        self.selector_label.setFixedHeight(20)
        selector_layout.addWidget(self.selector_label)

        selector_right_button = QPushButton(">")
        selector_right_button.setFixedHeight(20)
        selector_layout.addWidget(selector_right_button)

        self.file_type_combo = QComboBox()
        self.file_type_combo.addItem("csv")
        self.file_type_combo.addItem("ecg")
        self.file_type_combo.addItem("edf")
        self.file_type_combo.addItem("dat")
        self.file_type_combo.addItem("fit")
        self.file_type_combo.addItem("hea")
        self.file_type_combo.addItem("mat")
        self.file_type_combo.addItem("txt")
        self.file_type_combo.addItem("Other delimiter")
        self.file_type_combo.setFixedHeight(20)
        selector_layout.addWidget(self.file_type_combo)
        self.file_type_combo.currentTextChanged.connect(self.resetPath)

I made sure that each QDialog and QMainWindow is closed before opening the new one. And I know from debugging that a new QComboBox is properly created when calling the function request_user_input_database_and_file.
Does anyone have an idea of what can be the problem? I would really appreciate any help. Thank you

[jsulm]

@guillermollopis said in PyQT program crashes on Mac (not on Windows) when clicking on QComboBox:

def request_user_input_database_and_file(self):

    try: 
        app = QApplication(sys.argv)

Why do you create a new QApplication instance here? There should be only one QApplication instance.
It is also not clear how your main window and this dialog interact. Usually you instantiate a dialog from main window.

[guillermollopis]

@jsulm Thank you for your answer. I don't know why I wrote that line, but if I delete it I get the same error anyway. The main window is the class that contains the function request_user_input_database_and_file. When initialized, this function is called to open the QDialog. When the QDialog is closed, the function after_input() is called, where the QMainWindow is shown.

Maybe it's also relevant to add the crash report:

Crashed Thread:        0  Dispatch queue: com.apple.main-thread

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0x0000000000000028
Exception Codes:       0x0000000000000001, 0x0000000000000028
Exception Note:        EXC_CORPSE_NOTIFY

Termination Reason:    Namespace SIGNAL, Code 11 Segmentation fault: 11
Terminating Process:   exc handler [1820]

VM Region Info: 0x28 is not in any region.  Bytes before following region: 4311142360
      REGION TYPE                    START - END         [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL
      UNUSED SPACE AT START
--->  
      __TEXT                      100f6d000-100f79000    [   48K] r-x/r-x SM=COW  ...acOS/EZcardio

Thread 0 Crashed::  Dispatch queue: com.apple.main-thread
0   libqcocoa.dylib               	       0x1168c0c54 QCocoaWindow::view() const + 4
1   libqcocoa.dylib               	       0x1168f072f QCocoaInputContext::reset() + 79
2   QtWidgets                     	       0x10ef5959f QComboBox::showPopup() + 3071
3   QtWidgets.abi3.so             	       0x10e9d7345 sipQComboBox::showPopup() + 101
4   QtWidgets                     	       0x10ef5a91b QComboBoxPrivate::showPopupFromMouseEvent(QMouseEvent*) + 619
5   QtWidgets.abi3.so             	       0x10e9d8079 sipQComboBox::mousePressEvent(QMouseEvent*) + 121
6   QtWidgets                     	       0x10ee8fde8 QWidget::event(QEvent*) + 424
7   QtWidgets                     	       0x10ef5a634 QComboBox::event(QEvent*) + 372
8   QtWidgets.abi3.so             	       0x10e9d783f sipQComboBox::event(QEvent*) + 191
9   QtWidgets                     	       0x10ee559ea QApplicationPrivate::notify_helper(QObject*, QEvent*) + 266
10  QtWidgets                     	       0x10ee58755 QApplication::notify(QObject*, QEvent*) + 6965
11  QtWidgets.abi3.so             	       0x10e9f2e06 sipQApplication::notify(QObject*, QEvent*) + 230
12  QtCore                        	       0x10d6a9a34 QCoreApplication::notifyInternal2(QObject*, QEvent*) + 212
13  QtWidgets                     	       0x10ee56310 QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool, bool) + 896
14  QtWidgets                     	       0x10eeaf022 QWidgetWindow::handleMouseEvent(QMouseEvent*) + 3266
15  QtWidgets                     	       0x10eead6e9 QWidgetWindow::event(QEvent*) + 233
16  QtWidgets                     	       0x10ee559ea QApplicationPrivate::notify_helper(QObject*, QEvent*) + 266
17  QtWidgets                     	       0x10ee56e11 QApplication::notify(QObject*, QEvent*) + 497
18  QtWidgets.abi3.so             	       0x10e9f2e06 sipQApplication::notify(QObject*, QEvent*) + 230
19  QtCore                        	       0x10d6a9a34 QCoreApplication::notifyInternal2(QObject*, QEvent*) + 212
20  QtGui                         	       0x10e244e2e QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent*) + 3534
21  QtGui                         	       0x10e229d7b QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 219
22  libqcocoa.dylib               	       0x1168d9260 QCocoaEventDispatcherPrivate::processPostedEvents() + 320
23  libqcocoa.dylib               	       0x1168d99c8 QCocoaEventDispatcherPrivate::postedEventsSourceCallback(void*) + 40
24  CoreFoundation                	    0x7ff81562cc08 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
25  CoreFoundation                	    0x7ff81562cb70 __CFRunLoopDoSource0 + 180
26  CoreFoundation                	    0x7ff81562c8e3 __CFRunLoopDoSources0 + 242
27  CoreFoundation                	    0x7ff81562b2ff __CFRunLoopRun + 897
28  CoreFoundation                	    0x7ff81562a8a9 CFRunLoopRunSpecific + 567
29  HIToolbox                     	    0x7ff81e6b64f1 RunCurrentEventLoopInMode + 292
30  HIToolbox                     	    0x7ff81e6b6118 ReceiveNextEventCommon + 284
31  HIToolbox                     	    0x7ff81e6b5fe5 _BlockUntilNextEventMatchingListInModeWithFilter + 70
32  AppKit                        	    0x7ff817f80d88 _DPSNextEvent + 886
33  AppKit                        	    0x7ff817f7f3f4 -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 1411
34  AppKit                        	    0x7ff817f71919 -[NSApplication run] + 586
35  libqcocoa.dylib               	       0x1168d862f QCocoaEventDispatcher::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 2495
36  QtCore                        	       0x10d6a5acf QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 431
37  QtCore                        	       0x10d6aa042 QCoreApplication::exec() + 130
38  QtWidgets.abi3.so             	       0x10eae40c2 meth_QApplication_exec_(_object*, _object*) + 82
39  Python                        	       0x1020245c2 cfunction_call_varargs + 290
40  Python                        	       0x102023f85 _PyObject_MakeTpCall + 373
41  Python                        	       0x1020f2945 call_function + 533
42  Python                        	       0x1020ef74e _PyEval_EvalFrameDefault + 25678
43  Python                        	       0x1020248d0 function_code_fastcall + 128
44  Python                        	       0x1020f28ec call_function + 444
45  Python                        	       0x1020ef72a _PyEval_EvalFrameDefault + 25642
46  Python                        	       0x1020f3734 _PyEval_EvalCodeWithName + 2804
47  Python                        	       0x102024a6e _PyFunction_Vectorcall + 270
48  Python                        	       0x102023dd7 _PyObject_FastCallDict + 247
49  Python                        	       0x1020253df _PyObject_Call_Prepend + 143
50  Python                        	       0x10207b5e1 slot_tp_init + 145
51  Python                        	       0x102076a29 type_call + 297
52  Python                        	       0x102023f85 _PyObject_MakeTpCall + 373
53  Python                        	       0x1020f2945 call_function + 533
54  Python                        	       0x1020ef7e5 _PyEval_EvalFrameDefault + 25829
55  Python                        	       0x1020248d0 function_code_fastcall + 128
56  Python                        	       0x1020f28ec call_function + 444
57  Python                        	       0x1020ef72a _PyEval_EvalFrameDefault + 25642
58  Python                        	       0x1020248d0 function_code_fastcall + 128
59  Python                        	       0x1020f28ec call_function + 444
60  Python                        	       0x1020ef72a _PyEval_EvalFrameDefault + 25642
61  Python                        	       0x1020f3734 _PyEval_EvalCodeWithName + 2804
62  Python                        	       0x102024a6e _PyFunction_Vectorcall + 270
63  Python                        	       0x102023dd7 _PyObject_FastCallDict + 247
64  Python                        	       0x1020253df _PyObject_Call_Prepend + 143
65  Python                        	       0x10207b5e1 slot_tp_init + 145
66  Python                        	       0x102076a29 type_call + 297
67  Python                        	       0x102023f85 _PyObject_MakeTpCall + 373
68  Python                        	       0x1020f2945 call_function + 533
69  Python                        	       0x1020ef7e5 _PyEval_EvalFrameDefault + 25829
70  Python                        	       0x1020248d0 function_code_fastcall + 128
71  Python                        	       0x1020f28ec call_function + 444
72  Python                        	       0x1020ef7e5 _PyEval_EvalFrameDefault + 25829
73  Python                        	       0x1020f3734 _PyEval_EvalCodeWithName + 2804
74  Python                        	       0x1020e9224 PyEval_EvalCode + 100
75  EZcardio                      	       0x100f71a39 0x100f6d000 + 19001
76  EZcardio                      	       0x100f721e7 0x100f6d000 + 20967
77  dyld                          	       0x10f7204fe start + 462

Thread 1:
0   libsystem_pthread.dylib       	    0x7ff815561fec start_wqthread + 0

Thread 2:
0   libsystem_pthread.dylib       	    0x7ff815561fec start_wqthread + 0

Thread 3:
0   libsystem_pthread.dylib       	    0x7ff815561fec start_wqthread + 0

Thread 4:: com.apple.NSEventThread
0   libsystem_kernel.dylib        	    0x7ff815529aba mach_msg_trap + 10
1   libsystem_kernel.dylib        	    0x7ff815529e2b mach_msg + 59
2   CoreFoundation                	    0x7ff81562cdf1 __CFRunLoopServiceMachPort + 319
3   CoreFoundation                	    0x7ff81562b4af __CFRunLoopRun + 1329
4   CoreFoundation                	    0x7ff81562a8a9 CFRunLoopRunSpecific + 567
5   AppKit                        	    0x7ff8180eefd8 _NSEventThread + 132
6   libsystem_pthread.dylib       	    0x7ff8155664f4 _pthread_start + 125
7   libsystem_pthread.dylib       	    0x7ff81556200f thread_start + 15

Thread 5:
0   libsystem_pthread.dylib       	    0x7ff815561fec start_wqthread + 0

Thread 6:
0   libsystem_pthread.dylib       	    0x7ff815561fec start_wqthread + 0

Thread 7:
0   libsystem_pthread.dylib       	    0x7ff815561fec start_wqthread + 0

[jsulm]

@guillermollopis If you want to show the dialog as a blocking one then you should do

def request_user_input_database_and_file(self):
    mainWindow = MyMainImport(self) # Why mainWindow if it is a dialog?!
    mainWindow.exec()

instead of doing strange hacks.

[guillermollopis]

@jsulm I tried that as well but I still find the same problem. Also, I just get the error when using Mac, not Windows

[jsulm]

@guillermollopis said in PyQT program crashes on Mac (not on Windows) when clicking on QComboBox:

Also, I just get the error when using Mac, not Windows

Well, it can work on one platform but fail on another.
Can you provide a minimal reproducible example showing this behaviour?
I could try on my Mac.