fix(compat): support Qt 5.11 and GCC 8 toolchain

CMakeLists.txt

@@ -5,6 +5,12 @@ project(dde-cooperation VERSION 0.1 LANGUAGES CXX)
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+# GCC 8 (UOS 20) keeps std::filesystem in a separate archive, GCC >= 9 folds it
+# into libstdc++ and the separate archive may no longer exist.
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
+    set(CMAKE_CXX_STANDARD_LIBRARIES "${CMAKE_CXX_STANDARD_LIBRARIES} -lstdc++fs")
+endif()
+
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 
 if (NOT WIN32)

src/lib/common/manager/tunnelmanager.cpp

@@ -267,7 +267,12 @@ void TunnelManager::setupSocket(Stream *stream)
     connect(socket, &QTcpSocket::disconnected, this, [this, id] {
         destroyStream(id, "socket closed", true);
     });
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 15, 0))
     connect(socket, &QTcpSocket::errorOccurred, this, [this, id](QAbstractSocket::SocketError error) {
+#else
+    connect(socket, QOverload<QAbstractSocket::SocketError>::of(&QAbstractSocket::error), this,
+            [this, id](QAbstractSocket::SocketError error) {
+#endif
         Q_UNUSED(error)
         Stream *stream = findStream(id);
         if (!stream)

src/lib/cooperation/core/net/helper/sharehelper.cpp

@@ -706,8 +706,14 @@ void ShareHelperPrivate::probeBarrierServer(const QString &ip, int attemptsLeft)
         startClientBarrier();
     });
 
+    // Error handling function
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 15, 0))
     connect(socket, &QTcpSocket::errorOccurred, this,
             [this, ip, attemptsLeft, finish](QAbstractSocket::SocketError error) {
+#else
+    connect(socket, QOverload<QAbstractSocket::SocketError>::of(&QAbstractSocket::error), this,
+            [this, ip, attemptsLeft, finish](QAbstractSocket::SocketError error) {
+#endif
         Q_UNUSED(error)
         if (!finish())
             return;