CppEditor: Cancel runner in ~CppUseSelectionsUpdater

...otherwise an already destructed QTextDocument might be accessed in
the ClangCodeModel::Internal::IpcReceiver::references.

Task-number: QTCREATORBUG-18459
Change-Id: I1868b2fd3a64341794f83eea6c4eeb7c2c1af812
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangbackendipcintegration.cpp

@@ -248,9 +248,9 @@ void IpcReceiver::references(const ReferencesMessage &message)
     QTC_CHECK(futureInterface != QFutureInterface<CppTools::CursorInfo>());
 
     if (futureInterface.isCanceled())
-        return; // A new request was issued making this one outdated.
+        return; // Editor document closed or a new request was issued making this result outdated.
 
-    QTC_CHECK(entry.textDocument);
+    QTC_ASSERT(entry.textDocument, return);
     futureInterface.reportResult(toCursorInfo(*entry.textDocument, message));
     futureInterface.reportFinished();
 }

src/plugins/clangcodemodel/clangbackendipcintegration.h

@@ -35,6 +35,7 @@
 
 #include <QFuture>
 #include <QObject>
+#include <QPointer>
 #include <QSharedPointer>
 #include <QTextDocument>
 #include <QVector>
@@ -102,7 +103,7 @@ private:
             : futureInterface(futureInterface)
             , textDocument(textDocument) {}
         QFutureInterface<CppTools::CursorInfo> futureInterface;
-        QTextDocument *textDocument = nullptr;
+        QPointer<QTextDocument> textDocument;
     };
     QHash<quint64, ReferencesEntry> m_referencesTable;
 };

src/plugins/cppeditor/cppuseselectionsupdater.cpp

@@ -49,6 +49,12 @@ CppUseSelectionsUpdater::CppUseSelectionsUpdater(TextEditor::TextEditorWidget *e
     connect(&m_timer, &QTimer::timeout, this, [this]() { update(); });
 }
 
+CppUseSelectionsUpdater::~CppUseSelectionsUpdater()
+{
+    if (m_runnerWatcher)
+        m_runnerWatcher->cancel();
+}
+
 void CppUseSelectionsUpdater::scheduleUpdate()
 {
     m_timer.start();

src/plugins/cppeditor/cppuseselectionsupdater.h

@@ -44,6 +44,7 @@ class CppUseSelectionsUpdater : public QObject
 
 public:
     explicit CppUseSelectionsUpdater(TextEditor::TextEditorWidget *editorWidget);
+    ~CppUseSelectionsUpdater();
 
     void scheduleUpdate();
     void abortSchedule();