XCB: Don't core-dump if we can't connect to the X displayName

Exit with error, but don't crash.

Change-Id: Ie05c6480d8a44fda817ffffd14d9dfd8c951beef
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

3 files changed, 30 insertions, 8 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index e167ba1231..d36a14b920 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -571,9 +571,10 @@ QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, bool canGra
     m_connection = xcb_connect(m_displayName.constData(), &m_primaryScreenNumber);
 #endif // QT_CONFIG(xcb_xlib)
 
-    if (Q_UNLIKELY(!m_connection || xcb_connection_has_error(m_connection)))
-        qFatal("QXcbConnection: Could not connect to display %s", m_displayName.constData());
-
+    if (Q_UNLIKELY(!m_connection || xcb_connection_has_error(m_connection))) {
+        qCWarning(lcQpaScreen, "QXcbConnection: Could not connect to display %s", m_displayName.constData());
+        return;
+    }
 
     m_reader = new QXcbEventReader(this);
     m_reader->start();
@@ -668,7 +669,7 @@ QXcbConnection::~QXcbConnection()
     finalizeXInput2();
 #endif
 
-    if (m_reader->isRunning()) {
+    if (m_reader && m_reader->isRunning()) {
         sendConnectionEvent(QXcbAtom::_QT_CLOSE_CONNECTION);
         m_reader->wait();
     }
@@ -685,15 +686,22 @@ QXcbConnection::~QXcbConnection()
 
     delete m_glIntegration;
 
+    if (isConnected()) {
 #if QT_CONFIG(xcb_xlib)
-    XCloseDisplay(static_cast<Display *>(m_xlib_display));
+        XCloseDisplay(static_cast<Display *>(m_xlib_display));
 #else
-    xcb_disconnect(xcb_connection());
+        xcb_disconnect(xcb_connection());
 #endif
+    }
 
     delete m_keyboard;
 }
 
+bool QXcbConnection::isConnected() const
+{
+    return m_connection && !xcb_connection_has_error(m_connection);
+}
+
 QXcbScreen *QXcbConnection::primaryScreen() const
 {
     if (!m_screens.isEmpty()) {
diff --git a/src/plugins/platforms/xcb/qxcbconnection.h b/src/plugins/platforms/xcb/qxcbconnection.h
index 1129090eca..edbc8d846e 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.h
+++ b/src/plugins/platforms/xcb/qxcbconnection.h
@@ -388,6 +388,7 @@ public:
     ~QXcbConnection();
 
     QXcbConnection *connection() const { return const_cast<QXcbConnection *>(this); }
+    bool isConnected() const;
 
     const QList<QXcbVirtualDesktop *> &virtualDesktops() const { return m_virtualDesktops; }
     const QList<QXcbScreen *> &screens() const { return m_screens; }
diff --git a/src/plugins/platforms/xcb/qxcbintegration.cpp b/src/plugins/platforms/xcb/qxcbintegration.cpp
index b372ecd7c4..c9ecdceb0d 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.cpp
+++ b/src/plugins/platforms/xcb/qxcbintegration.cpp
@@ -178,12 +178,25 @@ QXcbIntegration::QXcbIntegration(const QStringList &parameters, int &argc, char
 
     const int numParameters = parameters.size();
     m_connections.reserve(1 + numParameters / 2);
-    m_connections << new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, displayName);
+    auto conn = new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, displayName);
+    if (conn->isConnected())
+        m_connections << conn;
+    else
+        delete conn;
 
     for (int i = 0; i < numParameters - 1; i += 2) {
         qCDebug(lcQpaScreen) << "connecting to additional display: " << parameters.at(i) << parameters.at(i+1);
         QString display = parameters.at(i) + QLatin1Char(':') + parameters.at(i+1);
-        m_connections << new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, display.toLatin1().constData());
+        conn = new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, display.toLatin1().constData());
+        if (conn->isConnected())
+            m_connections << conn;
+        else
+            delete conn;
+    }
+
+    if (m_connections.isEmpty()) {
+        qCritical("Could not connect to any X display.");
+        exit(1);
     }
 
     m_fontDatabase.reset(new QGenericUnixFontDatabase());