qt update checker: do not keep main window ref so it can gc-ed

related: #4905

electrum/gui/qt/main_window.py

@@ -299,7 +299,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
                     self.update_check_button.setText(_("Update to Electrum {} is available").format(v))
                     self.update_check_button.clicked.connect(lambda: self.show_update_check(v))
                     self.update_check_button.show()
-            self._update_check_thread = UpdateCheckThread(self)
+            self._update_check_thread = UpdateCheckThread()
             self._update_check_thread.checked.connect(on_version_received)
             self._update_check_thread.start()
 
@@ -465,6 +465,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
     def close_wallet(self):
         if self.wallet:
             self.logger.info(f'close_wallet {self.wallet.storage.path}')
+            self.wallet.thread = None
         run_hook('close_wallet', self.wallet)
 
     @profiler
@@ -758,7 +759,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
                            _("Uses icons from the Icons8 icon pack (icons8.com).")))
 
     def show_update_check(self, version=None):
-        self.gui_object._update_check = UpdateCheck(self, version)
+        self.gui_object._update_check = UpdateCheck(latest_version=version)
 
     def show_report_bug(self):
         msg = ' '.join([

electrum/gui/qt/update_checker.py

@@ -16,6 +16,7 @@ from electrum import ecc
 from electrum.i18n import _
 from electrum.util import make_aiohttp_session
 from electrum.logging import Logger
+from electrum.network import Network
 
 
 class UpdateCheck(QDialog, Logger):
@@ -26,8 +27,7 @@ class UpdateCheck(QDialog, Logger):
         "13xjmVAB1EATPP8RshTE8S8sNwwSUM9p1P",
     )
 
-    def __init__(self, main_window, latest_version=None):
+    def __init__(self, *, latest_version=None):
-        self.main_window = main_window
         QDialog.__init__(self)
         self.setWindowTitle('Electrum - ' + _('Update Check'))
         self.content = QVBoxLayout()
@@ -54,7 +54,7 @@ class UpdateCheck(QDialog, Logger):
 
         self.update_view(latest_version)
 
-        self.update_check_thread = UpdateCheckThread(self.main_window)
+        self.update_check_thread = UpdateCheckThread()
         self.update_check_thread.checked.connect(self.on_version_retrieved)
         self.update_check_thread.failed.connect(self.on_retrieval_failed)
         self.update_check_thread.start()
@@ -97,15 +97,15 @@ class UpdateCheckThread(QThread, Logger):
     checked = pyqtSignal(object)
     failed = pyqtSignal()
 
-    def __init__(self, main_window):
+    def __init__(self):
         QThread.__init__(self)
         Logger.__init__(self)
-        self.main_window = main_window
+        self.network = Network.get_instance()
 
     async def get_update_info(self):
         # note: Use long timeout here as it is not critical that we get a response fast,
         #       and it's bad not to get an update notification just because we did not wait enough.
-        async with make_aiohttp_session(proxy=self.main_window.network.proxy, timeout=120) as session:
+        async with make_aiohttp_session(proxy=self.network.proxy, timeout=120) as session:
             async with session.get(UpdateCheck.url) as result:
                 signed_version_dict = await result.json(content_type=None)
                 # example signed_version_dict:
@@ -131,12 +131,11 @@ class UpdateCheckThread(QThread, Logger):
                 return StrictVersion(version_num.strip())
 
     def run(self):
-        network = self.main_window.network
+        if not self.network:
-        if not network:
             self.failed.emit()
             return
         try:
-            update_info = asyncio.run_coroutine_threadsafe(self.get_update_info(), network.asyncio_loop).result()
+            update_info = asyncio.run_coroutine_threadsafe(self.get_update_info(), self.network.asyncio_loop).result()
         except Exception as e:
             self.logger.info(f"got exception: '{repr(e)}'")
             self.failed.emit()