From 1c7adf5addf82bc35784621d4f5b1217220ccfa2 Mon Sep 17 00:00:00 2001
From: Nick Bolton <nick@symless.com>
Date: Mon, 10 Feb 2025 17:59:43 +0000
Subject: [PATCH] refactor: Allocate daemon app and it's thread on stack to
 reduce memory leak risk

---
 src/apps/deskflow-daemon/deskflow-daemon.cpp | 44 ++++++++++----------
 1 file changed, 23 insertions(+), 21 deletions(-)

diff --git a/src/apps/deskflow-daemon/deskflow-daemon.cpp b/src/apps/deskflow-daemon/deskflow-daemon.cpp
index a840cb053..204467d4c 100644
--- a/src/apps/deskflow-daemon/deskflow-daemon.cpp
+++ b/src/apps/deskflow-daemon/deskflow-daemon.cpp
@@ -44,10 +44,8 @@ int main(int argc, char **argv)
 
   LOG((CLOG_PRINT "%s daemon (v%s)", kAppName, kVersion));
 
-  QCoreApplication app(argc, argv);
-
-  const auto pDaemon = &DaemonApp::instance();
-  const auto initResult = pDaemon->init(&events, argc, argv);
+  auto &daemon = DaemonApp::instance();
+  const auto initResult = daemon.init(&events, argc, argv);
 
   switch (initResult) {
     using enum DaemonApp::InitResult;
@@ -55,41 +53,45 @@ int main(int argc, char **argv)
   case StartDaemon: {
     QCoreApplication app(argc, argv);
 
-    // Thread must be heap-allocated for deferred deletion on thread exit.
-    // Avoid setting Qt ownership to prevent premature deletion (thread may run longer than Qt loop).
-    auto *pDaemonThread = new QThread(); // NOSONAR - Qt memory
-    pDaemon->moveToThread(pDaemonThread);
+    QThread daemonThread;
+    daemon.moveToThread(&daemonThread);
 
-    QObject::connect(pDaemonThread, &QThread::started, pDaemon, &DaemonApp::run);
-    QObject::connect(pDaemonThread, &QThread::finished, pDaemon, &QObject::deleteLater);
-    QObject::connect(pDaemonThread, &QThread::finished, pDaemonThread, &QThread::deleteLater);
-    QObject::connect(pDaemonThread, &QThread::finished, QCoreApplication::instance(), &QCoreApplication::quit);
+    QObject::connect(&daemonThread, &QThread::started, [&daemon, &daemonThread]() {
+      daemon.run();
+      daemonThread.quit();
+    });
+    QObject::connect(&daemonThread, &QThread::finished, &app, &QCoreApplication::quit);
 
-    // The daemon app is on it's own thread which doesn't have a Qt event loop, so we need to use direct connection.
-    auto *ipcServer = new ipc::DaemonIpcServer(&app, QString::fromStdString(pDaemon->logFilename())); // NOSONAR
+    ipc::DaemonIpcServer ipcServer(&app, QString::fromStdString(daemon.logFilename()));
+
+    // Use direct connection as the daemon app is on it's own thread, and so is on a different event loop.
     QObject::connect(
-        ipcServer, &ipc::DaemonIpcServer::logLevelChanged, pDaemon, &DaemonApp::saveLogLevel, //
+        &ipcServer, &ipc::DaemonIpcServer::logLevelChanged, &daemon, &DaemonApp::saveLogLevel, //
         Qt::DirectConnection
     );
     QObject::connect(
-        ipcServer, &ipc::DaemonIpcServer::elevateModeChanged, pDaemon, &DaemonApp::setElevate, //
+        &ipcServer, &ipc::DaemonIpcServer::elevateModeChanged, &daemon, &DaemonApp::setElevate, //
         Qt::DirectConnection
     );
     QObject::connect(
-        ipcServer, &ipc::DaemonIpcServer::commandChanged, pDaemon, &DaemonApp::setCommand, //
+        &ipcServer, &ipc::DaemonIpcServer::commandChanged, &daemon, &DaemonApp::setCommand, //
         Qt::DirectConnection
     );
     QObject::connect(
-        ipcServer, &ipc::DaemonIpcServer::startProcessRequested, pDaemon, &DaemonApp::applyWatchdogCommand, //
+        &ipcServer, &ipc::DaemonIpcServer::startProcessRequested, &daemon, &DaemonApp::applyWatchdogCommand, //
         Qt::DirectConnection
     );
     QObject::connect(
-        ipcServer, &ipc::DaemonIpcServer::stopProcessRequested, pDaemon, &DaemonApp::clearWatchdogCommand, //
+        &ipcServer, &ipc::DaemonIpcServer::stopProcessRequested, &daemon, &DaemonApp::clearWatchdogCommand, //
         Qt::DirectConnection
     );
 
-    pDaemonThread->start();
-    return QCoreApplication::exec();
+    daemonThread.start();
+    const auto exitCode = QCoreApplication::exec();
+    daemonThread.wait();
+
+    LOG_DEBUG("daemon exited, code: %d", exitCode);
+    return exitCode;
   }
 
   case FatalError: