Merge pull request #4581

Vincas Dargis (1):
      fix(platform): handle terminating POSIX signals

CMakeLists.txt

@@ -450,6 +450,13 @@ elseif (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
   )
 endif()
 
+if (UNIX)
+  set(${PROJECT_NAME}_SOURCES ${${PROJECT_NAME}_SOURCES}
+    src/platform/posixsignalnotifier.cpp
+    src/platform/posixsignalnotifier.h
+  )
+endif()
+
 if (PLATFORM_EXTENSIONS)
   set(${PROJECT_NAME}_SOURCES ${${PROJECT_NAME}_SOURCES}
     src/platform/autorun.h

src/main.cpp

@@ -46,6 +46,10 @@
 #include "platform/install_osx.h"
 #endif
 
+#if defined(Q_OS_UNIX)
+#include "platform/posixsignalnotifier.h"
+#endif
+
 #ifdef LOG_TO_FILE
 static QAtomicPointer<FILE> logFileFile = nullptr;
 static QList<QByteArray>* logBuffer =
@@ -145,6 +149,17 @@ int main(int argc, char* argv[])
     qInstallMessageHandler(logMessageHandler);
 
     QApplication* a = new QApplication(argc, argv);
+
+#if defined(Q_OS_UNIX)
+    // PosixSignalNotifier is used only for terminating signals,
+    // so it's connected directly to quit() without any filtering.
+    QObject::connect(&PosixSignalNotifier::globalInstance(),
+                     &PosixSignalNotifier::activated,
+                     a,
+                     &QApplication::quit);
+    PosixSignalNotifier::watchCommonTerminatingSignals();
+#endif
+
     a->setApplicationName("qTox");
     a->setOrganizationName("Tox");
     a->setApplicationVersion("\nGit commit: " + QString(GIT_VERSION));

src/platform/posixsignalnotifier.cpp

@@ -0,0 +1,126 @@
+/*
+    Copyright © 2017 by The qTox Project Contributors
+
+    This file is part of qTox, a Qt-based graphical interface for Tox.
+
+    qTox is libre software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    qTox is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with qTox.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "posixsignalnotifier.h"
+
+#include <QDebug>
+#include <QSocketNotifier>
+
+#include <array>
+#include <atomic>
+
+#include <errno.h>
+#include <signal.h>     // sigaction()
+#include <sys/socket.h> // socketpair()
+#include <sys/types.h>  // may be needed for BSD
+#include <unistd.h>     // close()
+
+/**
+ * @class PosixSignalNotifier
+ * @brief Class for converting POSIX signals to Qt signals
+ */
+
+namespace detail {
+
+static std::atomic_flag g_signalSocketUsageFlag{ATOMIC_FLAG_INIT};
+static std::array<int, 2> g_signalSocketPair;
+
+static void signalHandler(int signum)
+{
+    // DO NOT call any Qt functions directly, only limited amount of so-called async-signal-safe
+    // functions can be called in signal handlers.
+    // See https://doc.qt.io/qt-4.8/unix-signals.html
+
+    // If test_and_set() returns true, it means it was already in use (only by ~PosixSignalNotifier()),
+    // so we bail out. Our signal handler is blocking, only one will be called (no race between
+    // threads), hence simple implementation.
+    if (g_signalSocketUsageFlag.test_and_set())
+        return;
+
+    ::write(g_signalSocketPair[0], &signum, sizeof(signum));
+
+    g_signalSocketUsageFlag.clear();
+}
+
+} // namespace detail
+
+PosixSignalNotifier::~PosixSignalNotifier()
+{
+    while (detail::g_signalSocketUsageFlag.test_and_set()) {
+        // spin-loop until we aquire flag (signal handler might be running and have flag in use)
+    }
+
+    // do not leak sockets
+    ::close(detail::g_signalSocketPair[0]);
+    ::close(detail::g_signalSocketPair[1]);
+
+    // do not clear the usage flag here, signal handler cannot use socket any more!
+}
+
+void PosixSignalNotifier::watchSignal(int signum)
+{
+    sigset_t blockMask;
+    sigemptyset(&blockMask); // do not prefix with ::, it's a macro on macOS
+    sigaddset(&blockMask, signum); // do not prefix with ::, it's a macro on macOS
+
+    struct sigaction action = {}; // all zeroes by default
+    action.sa_handler = detail::signalHandler;
+    action.sa_mask = blockMask; // allow old signal to finish before new is raised
+
+    if (::sigaction(signum, &action, 0)) {
+        qFatal("Failed to setup signal %d, error = %d", signum, errno);
+    }
+}
+
+void PosixSignalNotifier::watchSignals(std::initializer_list<int> signalSet)
+{
+    for (auto s: signalSet) {
+        watchSignal(s);
+    }
+}
+
+void PosixSignalNotifier::watchCommonTerminatingSignals()
+{
+    watchSignals({SIGHUP, SIGINT, SIGQUIT, SIGTERM});
+}
+
+PosixSignalNotifier& PosixSignalNotifier::globalInstance()
+{
+    static PosixSignalNotifier instance;
+    return instance;
+}
+
+void PosixSignalNotifier::onSignalReceived()
+{
+    int signum{0};
+    ::read(detail::g_signalSocketPair[1], &signum, sizeof(signum));
+
+    qDebug() << "Signal" << signum << "received";
+    emit activated(signum);
+}
+
+PosixSignalNotifier::PosixSignalNotifier()
+{
+    if (::socketpair(AF_UNIX, SOCK_STREAM, 0, detail::g_signalSocketPair.data())) {
+       qFatal("Failed to create socket pair, error = %d", errno);
+    }
+
+    notifier = new QSocketNotifier(detail::g_signalSocketPair[1], QSocketNotifier::Read, this);
+    connect(notifier, &QSocketNotifier::activated, this, &PosixSignalNotifier::onSignalReceived);
+}

src/platform/posixsignalnotifier.h

@@ -0,0 +1,53 @@
+/*
+    Copyright © 2017 by The qTox Project Contributors
+
+    This file is part of qTox, a Qt-based graphical interface for Tox.
+
+    qTox is libre software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    qTox is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with qTox.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef POSIXSIGNALNOTIFIER_H
+#define POSIXSIGNALNOTIFIER_H
+
+#include <QObject>
+
+class QSocketNotifier;
+
+class PosixSignalNotifier : public QObject
+{
+    Q_OBJECT
+
+public:
+    ~PosixSignalNotifier();
+
+    static void watchSignal(int signum);
+    static void watchSignals(std::initializer_list<int> signalSet);
+    static void watchCommonTerminatingSignals();
+
+    static PosixSignalNotifier& globalInstance();
+
+signals:
+    void activated(int signal);
+
+private slots:
+    void onSignalReceived();
+
+private:
+    PosixSignalNotifier();
+
+private:
+    QSocketNotifier* notifier{nullptr};
+};
+
+#endif // POSIXSIGNALNOTIFIER_H