CODEWITHSUNDEEP
pythonpyqt
ymmx
ymmx

Reputation: 4967

Segmentation fault: 11 on a QMainWindow exit button with pyqt5 on OSX

I get a strange behavior that's happening on OSX but not on Windows.

I made a software with pyqt5 and when I close a child window I have a crash with "Segmentation fault: 11"

To explain better, I have a main window where I may open other windows to ask to the user some info. the error is happening when I close that second window.

I have a closeEvent function : 

def closeEvent(self, event):
    self.Close_OBJ.emit()
    self.close()

which send a pyqtSignalto the main window.

If I comment the self.Close_OBJ.emit()I don't have the Segmentation fault anymore, but I need this so my main window can react to the closing of that child window.

What is also confusing is that I have other child windows where I have the same closeEvent function and it's work well. I don't understand why I don't have this issue on Windows OS.

Here's a minimal example of the issue:

from PyQt5.QtGui import *
from PyQt5.QtWidgets import  *
from PyQt5.QtCore import *
import sys


class Modify_1_NMM(QMainWindow):
    Close_OBJ = pyqtSignal()
    def __init__(self,):
        super(Modify_1_NMM, self).__init__()
        self.centralWidget = QWidget()
        self.setCentralWidget(self.centralWidget)
        self.mainHBOX_param_scene = QHBoxLayout()
        self.label = QLabel('Please, close this window')
        self.mainHBOX_param_scene.addWidget(self.label)
        self.centralWidget.setLayout(self.mainHBOX_param_scene)

    def closeEvent(self, event):
        self.Close_OBJ.emit()
        self.close()


class StimEdit(QMainWindow):
    def __init__(self, parent=None):
        super(StimEdit, self).__init__()
        self.NewModifyXNMM = None
        self.centralWidget = QWidget()
        self.setCentralWidget(self.centralWidget)
        self.mainHBOX_param_scene = QHBoxLayout()

        self.B = QPushButton('clik here to open o window')
        self.B.setFixedSize(400,200)
        self.B.clicked.connect(self.ModXNMMclicked)
        self.mainHBOX_param_scene.addWidget(self.B)
        self.centralWidget.setLayout(self.mainHBOX_param_scene)


    def ModXNMMclicked(self,):
        if self.NewModifyXNMM  == None:
            self.NewModifyXNMM = Modify_1_NMM()
            self.NewModifyXNMM.Close_OBJ.connect(self.close_ModXNMM)
            self.NewModifyXNMM.show()


    @pyqtSlot()
    def close_ModXNMM(self):
        print('about to close',self)
        self.NewModifyXNMM = None
        print('did closed')



def main():
    app = QApplication(sys.argv)
    ex = StimEdit(app)
    ex.show()
    sys.exit(app.exec_( ))


if __name__ == '__main__':
    main()

when I click on the button on the main window, a second window opens. When I then close the second window, it crashes (not even all the time... but most of the time).

On pycharm I get this error message :

about to close <__main__.StimEdit object at 0x103f0af78>
did closed
Process finished with exit code 139 (interrupted by signal 11: SIGSEGV)

and on the terminal I get: 

about to close <__main__.StimEdit object at 0x10c706288>
did closed
Segmentation fault: 11

UPDATE

if I comment out the line self.NewModifyXNMM = None I don't have the segmentation fault anymore. Is it possible this line is in conflict with the window closing?

Upvotes: 1

Views: 1341

Answers (1)

eyllanesc
eyllanesc

Reputation: 243983

It seems that the object reference is being lost when you set a None to the variable, a possible workaround is to use deleteLater and the destroyed signal:

@pyqtSlot()
def close_ModXNMM(self):
    print('about to close',self)
    self.NewModifyXNMM.deleteLater()
    self.NewModifyXNMM.destroyed.connect(self.on_destroyed)
    print('did closed')

@pyqtSlot('QObject*')
def on_destroyed(self, o):
    self.NewModifyXNMM = None
    print(self.NewModifyXNMM)

Upvotes: 1

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