Using signal/slot transfer data from sub thread to main thread，however，the applicaiton always crash！：（

[jowei]

Hi everyone,
I am creating an application that create a sub thread to setup data, then send the data to main thread to show by signal/slot, however, the application always crash, here is my code:
GUI.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QPushButton" name="btn_start_">
    <property name="geometry">
     <rect>
      <x>190</x>
      <y>40</y>
      <width>75</width>
      <height>23</height>
     </rect>
    </property>
    <property name="text">
     <string>Start</string>
    </property>
   </widget>
   <widget class="QPushButton" name="btn_exit_">
    <property name="geometry">
     <rect>
      <x>310</x>
      <y>40</y>
      <width>75</width>
      <height>23</height>
     </rect>
    </property>
    <property name="text">
     <string>Exit</string>
    </property>
   </widget>
   <widget class="QPlainTextEdit" name="plainTextEdit">
    <property name="geometry">
     <rect>
      <x>140</x>
      <y>90</y>
      <width>541</width>
      <height>351</height>
     </rect>
    </property>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>800</width>
     <height>23</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

GUI.py

# -*- coding: utf-8 -*-

################################################################################
## Form generated from reading UI file 'main_window.ui'
##
## Created by: Qt User Interface Compiler version 5.15.2
##
## WARNING! All changes made in this file will be lost when recompiling UI file!
################################################################################

from PySide2.QtCore import *
from PySide2.QtGui import *
from PySide2.QtWidgets import *


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        if not MainWindow.objectName():
            MainWindow.setObjectName(u"MainWindow")
        MainWindow.resize(800, 600)
        self.centralwidget = QWidget(MainWindow)
        self.centralwidget.setObjectName(u"centralwidget")
        self.btn_start_ = QPushButton(self.centralwidget)
        self.btn_start_.setObjectName(u"btn_start_")
        self.btn_start_.setGeometry(QRect(190, 40, 75, 23))
        self.btn_exit_ = QPushButton(self.centralwidget)
        self.btn_exit_.setObjectName(u"btn_exit_")
        self.btn_exit_.setGeometry(QRect(310, 40, 75, 23))
        self.plainTextEdit = QPlainTextEdit(self.centralwidget)
        self.plainTextEdit.setObjectName(u"plainTextEdit")
        self.plainTextEdit.setGeometry(QRect(140, 90, 541, 351))
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QMenuBar(MainWindow)
        self.menubar.setObjectName(u"menubar")
        self.menubar.setGeometry(QRect(0, 0, 800, 23))
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QStatusBar(MainWindow)
        self.statusbar.setObjectName(u"statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)

        QMetaObject.connectSlotsByName(MainWindow)
    # setupUi

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(QCoreApplication.translate("MainWindow", u"MainWindow", None))
        self.btn_start_.setText(QCoreApplication.translate("MainWindow", u"Start", None))
        self.btn_exit_.setText(QCoreApplication.translate("MainWindow", u"Exit", None))
    # retranslateUi

GUI frame inherited by GUI.py

# !/usr/bin/env python
# encoding: utf-8
# @File    : main_frame_module.py
# @Time    : 2021/6/16
# @Author  : qz
# @Version : 1.0
# @Email   : weiweiqiao@126.com
# @License : (C) Copyright 2013-2021
# @Brief   :


from PySide2.QtWidgets import QMainWindow
from PySide2.QtCore import QThread
from PySide2.QtCore import QObject
from PySide2.QtWidgets import QApplication
from PySide2.QtCore import Slot
from PySide2.QtCore import Signal
from pyside2_signal_slot_test.main_window import Ui_MainWindow
from pyside2_signal_slot_test.manager import Manager
from pyside2_signal_slot_test.data_module import Data


class MainWin(QMainWindow):
    def __init__(self, parent = None):
        QMainWindow.__init__(self, parent)
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

        self.__thread = QThread()
        self.__manager = Manager()
        self.__init_connect()


    def __init_connect(self):
        """
        链接信号槽
        Returns: None

        """
        # 点击退出程序按钮
        self.ui.btn_exit_.clicked.connect(self.__exit_application)
        # 点击启动按钮
        self.ui.btn_start_.clicked.connect(self.__do)
        self.si_send_do.connect(self.__manager.sl_slot)
        self.__manager.si_send_track.connect(self.__show_data)
        self.__manager.si_stop_sub_thread.connect(self.__sl_stop_sub_thread)


    def __start_thread(self, obj: QObject, thread: QThread):
        """
        启动子线程
        Args:
            obj: 迁移入子线程中的对象
            thread: 子线程

        Returns: None

        """
        if not thread.isRunning():
            obj.moveToThread(thread)
            thread.start()


    @Slot()
    def __exit_application(self):
        QApplication.closeAllWindows()


    @Slot()
    def __do(self):
        self.__start_thread(self.__manager, self.__thread)
        self.si_send_do.emit()


    @Slot(Data)
    def __show_data(self, data: Data):
        """
        根据传入的数据在文本框中显示
        Args:
            data: 传入的数据对象

        Returns: None

        """
        # 获取是否显示标识符
        self.ui.plainTextEdit.appendPlainText(str(data.get_is_show()))


    @Slot(int)
    def __sl_stop_sub_thread(self, code: int):
        if 0 == code:
            self.__thread.exit()


    si_send_do = Signal()

Manager.py

# !/usr/bin/env python
# encoding: utf-8
# @File    : manager.py
# @Time    : 2021/6/16
# @Author  : qz
# @Version : 1.0
# @Email   : weiweiqiao@126.com
# @License : (C) Copyright 2013-2021
# @Brief   :


from PySide2.QtCore import QObject
from PySide2.QtCore import Slot
from PySide2.QtCore import Signal
from pyside2_signal_slot_test.data_module import Data


class Manager(QObject):
    def __init__(self):
        super().__init__()


    @Slot()
    def sl_slot(self):
        """
        生成数据对象，通过信号槽传递数据对象。退出当前线程（子线程）
        Returns: None

        """
        # 生成数据对象
        track = Data()
        track.setup_is_show(True)

        # 传递数据对象
        self.si_send_track.emit(track)

        # 发射信号，退出子线程
        self.si_stop_sub_thread.emit(0)


    # 传递Data类型数据
    si_send_track = Signal(Data)
    # 结束子线程
    si_stop_sub_thread = Signal(int)

Data.py

# !/usr/bin/env python
# encoding: utf-8
# @File    : data_module.py
# @Time    : 2021/6/14
# @Author  : qz
# @Version : 1.0
# @Email   : weiweiqiao@126.com
# @License : (C) Copyright 2013-2021
# @Brief   :


from PySide2.QtCore import QObject


class Data(QObject):
    def __init__(self):
        super(Data, self).__init__()
        # Dict instance
        self.__dict = {}
        self.__is_show = False
        self.__count = 0


    def setup_data(self, key: str, value: str):
        """
        更新__dict的数据
        Args:
            key: 关键字
            value: 数据

        Returns: None

        """
        self.__dict.update(key, value)


    def get_dict(self):
        return self.__dict


    def setup_is_show(self, flag: bool):
        self.__is_show = flag


    def get_is_show(self):
        return self.__is_show

Main.py

# !/usr/bin/env python
# encoding: utf-8
# @File    : main.py
# @Time    : 2021/6/16
# @Author  : qz
# @Version : 1.0
# @Email   : weiweiqiao@126.com
# @License : (C) Copyright 2013-2021
# @Brief   :


import sys
from PySide2.QtWidgets import QApplication
from pyside2_signal_slot_test.main_frame_module import MainWin


if __name__ == '__main__':
    app = QApplication(sys.argv)

    form = MainWin()
    form.show()

    sys.exit(app.exec_())

The application is always crashing and show "Process finished with exit code -1073741819 (0xC0000005)"

[SGaist]

Hi,

You should run your application through the debugger to see exactly where it crashes.

[jowei]

@SGaist
thx.
The crash only in "self.si_send_track.emit(track)" of "def sl_slot(self):" function in Manager.py after start sub thread in "self.__start_thread(self.__manager, self.__thread)" of "def __do(self):" function in GUI.py.
After comment "self.__start_thread(self.__manager, self.__thread)", the appliction is done well.

[SGaist]

What if you just print the parameter and nothing else in the slot ?

[jowei]

@SGaist
thx，I follow your mind.
I use None instead the parameter of TrackData. the application is well done, I print the instance of TrackData in "sl_slot" function of Manager class, the instance is not None. So I think custom type is the point :)
I have a question, Qt suggest that register custom type， it is useful in Pyside2?

[jowei]

I found the application is not crash every time, It is often well when runing the first time. :(

[SGaist]

Did you try to run your application through gdb to learn where exactly it crashed ?