Clang: Clear left-over preambles after crash

...otherwise they accumulate in the temporary directory.

Change-Id: I0841f3d168f30f559fc718d2825dd3e800515074
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/libs/clangbackendipc/connectionclient.cpp

@@ -43,6 +43,7 @@ namespace ClangBackEnd {
 ConnectionClient::ConnectionClient()
 {
     processAliveTimer.setInterval(10000);
+    resetTemporaryDir();
 
     static const bool startAliveTimer = !qEnvironmentVariableIntValue("QTC_CLANG_NO_ALIVE_TIMER");
 
@@ -113,9 +114,7 @@ QProcessEnvironment ConnectionClient::processEnvironment() const
 
 const QTemporaryDir &ConnectionClient::temporaryDirectory() const
 {
-    static QTemporaryDir temporaryDirectory(QDir::tempPath() + QStringLiteral("/qtc-clang-XXXXXX"));
-
-    return temporaryDirectory;
+    return *temporaryDirectory_.data();
 }
 
 LinePrefixer &ConnectionClient::stdErrPrefixer()
@@ -147,6 +146,7 @@ void ConnectionClient::restartProcessAsynchronously()
 {
     if (!processIsStarting) {
         finishProcess(std::move(process_));
+        resetTemporaryDir(); // clear left-over preambles
 
         startProcessAndConnectToServerAsynchronously();
     }
@@ -218,6 +218,12 @@ void ConnectionClient::printStandardError()
     qDebug("%s", stdErrPrefixer_.prefix(process_->readAllStandardError()).constData());
 }
 
+void ConnectionClient::resetTemporaryDir()
+{
+    const QString templatePath = QDir::tempPath() + QStringLiteral("/qtc-clang-XXXXXX");
+    temporaryDirectory_.reset(new QTemporaryDir(templatePath));
+}
+
 void ConnectionClient::connectLocalSocketConnected()
 {
     connect(&localSocket,

src/libs/clangbackendipc/connectionclient.h

@@ -30,6 +30,8 @@
 
 #include <QLocalSocket>
 #include <QProcessEnvironment>
+#include <QScopedPointer>
+#include <QTemporaryDir>
 
 #include <memory>
 
@@ -102,6 +104,8 @@ private:
     void printStandardOutput();
     void printStandardError();
 
+    void resetTemporaryDir();
+
     void connectLocalSocketConnected();
     void connectLocalSocketDisconnected();
     void connectProcessFinished(QProcess *process) const;
@@ -121,6 +125,7 @@ private:
 
     mutable std::unique_ptr<QProcess> process_;
     QLocalSocket localSocket;
+    QScopedPointer<QTemporaryDir> temporaryDirectory_;
     QTimer processAliveTimer;
     QString processPath_;
     bool isAliveTimerResetted = false;