diff --git a/src/plugins/coreplugin/documentmanager.cpp b/src/plugins/coreplugin/documentmanager.cpp
index 72f4d0e077fb6fbc50d37f51a0ff88c36b055e15..59775c51871af5fb86bf35ba74ae12d8c9e3f409 100644
--- a/src/plugins/coreplugin/documentmanager.cpp
+++ b/src/plugins/coreplugin/documentmanager.cpp
@@ -228,7 +228,7 @@ DocumentManager::~DocumentManager()
     delete d;
 }
 
-QObject *DocumentManager::instance()
+DocumentManager *DocumentManager::instance()
 {
     return m_instance;
 }
diff --git a/src/plugins/coreplugin/documentmanager.h b/src/plugins/coreplugin/documentmanager.h
index 1fc72b24b75aa7d88934ea64f789e2f34e706624..9c361910fba2eb27172911fa48301665955c1a6d 100644
--- a/src/plugins/coreplugin/documentmanager.h
+++ b/src/plugins/coreplugin/documentmanager.h
@@ -60,7 +60,7 @@ public:
 
     typedef QPair<QString, Id> RecentFile;
 
-    static QObject *instance();
+    static DocumentManager *instance();
 
     // file pool to monitor
     static void addDocuments(const QList<IDocument *> &documents, bool addWatcher = true);
diff --git a/src/plugins/cppeditor/cppincludehierarchy_test.cpp b/src/plugins/cppeditor/cppincludehierarchy_test.cpp
index ac208778710a0463485c73e2884d926f6a34f6f1..8eaba08c0a854467b64ad1f5eeeadcc148dc7cae 100644
--- a/src/plugins/cppeditor/cppincludehierarchy_test.cpp
+++ b/src/plugins/cppeditor/cppincludehierarchy_test.cpp
@@ -79,7 +79,7 @@ public:
     {
         QVERIFY(succeededSoFar());
 
-        QStringList filePaths;
+        QSet<QString> filePaths;
         const int sourceListSize = sourceList.size();
         for (int i = 0; i < sourceListSize; ++i) {
             const QByteArray &source = sourceList.at(i);
diff --git a/src/plugins/cppeditor/cppquickfix_test.cpp b/src/plugins/cppeditor/cppquickfix_test.cpp
index 827e4362a0c5e389fe826611228c503b26771c83..b1b4c947ae9d95e7a28ae926ca1999b99dbdab7a 100644
--- a/src/plugins/cppeditor/cppquickfix_test.cpp
+++ b/src/plugins/cppeditor/cppquickfix_test.cpp
@@ -145,7 +145,7 @@ QuickFixTestCase::QuickFixTestCase(const QList<QuickFixTestDocument::Ptr> &theTe
     }
 
     // Update Code Model
-    QStringList filePaths;
+    QSet<QString> filePaths;
     foreach (const QuickFixTestDocument::Ptr &testFile, m_testFiles)
         filePaths << testFile->filePath();
     QVERIFY(parseFiles(filePaths));
diff --git a/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp b/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp
index 87ea2fa0dbc3f60d97bca506e4eaf5346e0157dc..b3191ba031035877090db4d6d1fcbbddb5589203 100644
--- a/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp
+++ b/src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp
@@ -268,7 +268,7 @@ F2TestCase::F2TestCase(CppEditorAction action,
         QVERIFY(testFile->writeToDisk());
 
     // Update Code Model
-    QStringList filePaths;
+    QSet<QString> filePaths;
     foreach (const TestDocumentPtr &testFile, testFiles)
         filePaths << testFile->filePath();
     QVERIFY(parseFiles(filePaths));
diff --git a/src/plugins/cpptools/abstracteditorsupport.cpp b/src/plugins/cpptools/abstracteditorsupport.cpp
index bba88d4e95e2db39cfe7209ef9b8955cfd260223..d1abe0ff79e3e6ecad4e81e5fdf7cc0b1db5b6eb 100644
--- a/src/plugins/cpptools/abstracteditorsupport.cpp
+++ b/src/plugins/cpptools/abstracteditorsupport.cpp
@@ -49,7 +49,7 @@ AbstractEditorSupport::~AbstractEditorSupport()
 void AbstractEditorSupport::updateDocument()
 {
     ++m_revision;
-    m_modelmanager->updateSourceFiles(QStringList(fileName()));
+    m_modelmanager->updateSourceFiles(QSet<QString>() << fileName());
 }
 
 QString AbstractEditorSupport::functionAt(const CppModelManagerInterface *modelManager,
diff --git a/src/plugins/cpptools/baseeditordocumentprocessor.cpp b/src/plugins/cpptools/baseeditordocumentprocessor.cpp
index e8992da58e4c574dbad1004fe43480d59e7dc90c..f8353707fbe7b9b233fbde9a4e4350062939a0df 100644
--- a/src/plugins/cpptools/baseeditordocumentprocessor.cpp
+++ b/src/plugins/cpptools/baseeditordocumentprocessor.cpp
@@ -127,7 +127,7 @@ void BaseEditorDocumentProcessor::runParser(QFutureInterface<void> &future,
 
     parser->update(workingCopy);
     CppModelManagerInterface::instance()
-        ->finishedRefreshingSourceFiles(QStringList(parser->filePath()));
+        ->finishedRefreshingSourceFiles(QSet<QString>() << parser->filePath());
 
     future.setProgressValue(1);
 }
diff --git a/src/plugins/cpptools/builtinindexingsupport.cpp b/src/plugins/cpptools/builtinindexingsupport.cpp
index 47b771a6b29e6972517d3c181ee9b29f1c806f17..cd2386a6bb059c6b5300238e9f4a295d3f96d239 100644
--- a/src/plugins/cpptools/builtinindexingsupport.cpp
+++ b/src/plugins/cpptools/builtinindexingsupport.cpp
@@ -68,7 +68,7 @@ public:
     int revision;
     ProjectPart::HeaderPaths headerPaths;
     WorkingCopy workingCopy;
-    QStringList sourceFiles;
+    QSet<QString> sourceFiles;
 };
 
 class WriteTaskFileForDiagnostics
@@ -133,7 +133,7 @@ private:
     int m_processedDiagnostics;
 };
 
-void classifyFiles(const QStringList &files, QStringList *headers, QStringList *sources)
+void classifyFiles(const QSet<QString> &files, QStringList *headers, QStringList *sources)
 {
     foreach (const QString &file, files) {
         if (ProjectFile::isSource(ProjectFile::classify(file)))
@@ -145,11 +145,11 @@ void classifyFiles(const QStringList &files, QStringList *headers, QStringList *
 
 void indexFindErrors(QFutureInterface<void> &future, const ParseParams params)
 {
-    QStringList files = params.sourceFiles;
-    files.sort();
     QStringList sources, headers;
-    classifyFiles(files, &headers, &sources);
-    files = sources + headers;
+    classifyFiles(params.sourceFiles, &headers, &sources);
+    sources.sort();
+    headers.sort();
+    QStringList files = sources + headers;
 
     WriteTaskFileForDiagnostics taskFileWriter;
     QElapsedTimer timer;
@@ -196,20 +196,18 @@ void index(QFutureInterface<void> &future, const ParseParams params)
     sourceProcessor->setHeaderPaths(params.headerPaths);
     sourceProcessor->setWorkingCopy(params.workingCopy);
 
-    QStringList files = params.sourceFiles;
 
     QStringList sources;
     QStringList headers;
-    classifyFiles(files, &headers, &sources);
+    classifyFiles(params.sourceFiles, &headers, &sources);
 
-    foreach (const QString &file, files)
+    foreach (const QString &file, params.sourceFiles)
         sourceProcessor->removeFromCache(file);
 
     const int sourceCount = sources.size();
-    files = sources;
-    files += headers;
+    QStringList files = sources + headers;
 
-    sourceProcessor->setTodo(files);
+    sourceProcessor->setTodo(files.toSet());
 
     const QString conf = CppModelManagerInterface::configurationFileName();
     bool processingHeaders = false;
@@ -250,7 +248,7 @@ void index(QFutureInterface<void> &future, const ParseParams params)
 
 void parse(QFutureInterface<void> &future, const ParseParams params)
 {
-    const QStringList files = params.sourceFiles;
+    const QSet<QString> &files = params.sourceFiles;
     if (files.isEmpty())
         return;
 
@@ -356,7 +354,7 @@ BuiltinIndexingSupport::BuiltinIndexingSupport()
 BuiltinIndexingSupport::~BuiltinIndexingSupport()
 {}
 
-QFuture<void> BuiltinIndexingSupport::refreshSourceFiles(const QStringList &sourceFiles,
+QFuture<void> BuiltinIndexingSupport::refreshSourceFiles(const QSet<QString> &sourceFiles,
     CppModelManagerInterface::ProgressNotificationMode mode)
 {
     CppModelManager *mgr = CppModelManager::instance();
diff --git a/src/plugins/cpptools/builtinindexingsupport.h b/src/plugins/cpptools/builtinindexingsupport.h
index cf1e9beae76c0aab9f0a32691171cf2c8828cefb..a9a5d31d68d2979554aa625b2cfc6b76fbd36cad 100644
--- a/src/plugins/cpptools/builtinindexingsupport.h
+++ b/src/plugins/cpptools/builtinindexingsupport.h
@@ -43,7 +43,7 @@ public:
     BuiltinIndexingSupport();
     ~BuiltinIndexingSupport();
 
-    virtual QFuture<void> refreshSourceFiles(const QStringList &sourceFiles,
+    virtual QFuture<void> refreshSourceFiles(const QSet<QString> &sourceFiles,
         CppModelManagerInterface::ProgressNotificationMode mode);
     virtual SymbolSearcher *createSymbolSearcher(SymbolSearcher::Parameters parameters,
                                                  QSet<QString> fileNames);
diff --git a/src/plugins/cpptools/cppfindreferences.cpp b/src/plugins/cpptools/cppfindreferences.cpp
index 27bd536a400e54fbbe184a025b39aefb3fc9d745..6e0ec85edee9033dc3ef6a7b307b1007a73a894b 100644
--- a/src/plugins/cpptools/cppfindreferences.cpp
+++ b/src/plugins/cpptools/cppfindreferences.cpp
@@ -385,7 +385,7 @@ void CppFindReferences::onReplaceButtonClicked(const QString &text,
 {
     const QStringList fileNames = TextEditor::BaseFileFind::replaceAll(text, items, preserveCase);
     if (!fileNames.isEmpty()) {
-        m_modelManager->updateSourceFiles(fileNames);
+        m_modelManager->updateSourceFiles(fileNames.toSet());
         Core::SearchResultWindow::instance()->hide();
     }
 }
diff --git a/src/plugins/cpptools/cppindexingsupport.h b/src/plugins/cpptools/cppindexingsupport.h
index bd50dfc6361d9b57c29a185f9f0450d3c7c5286e..b31e5072a2701a209e9603cd01ade89214f6cc5c 100644
--- a/src/plugins/cpptools/cppindexingsupport.h
+++ b/src/plugins/cpptools/cppindexingsupport.h
@@ -82,7 +82,7 @@ class CPPTOOLS_EXPORT CppIndexingSupport
 public:
     virtual ~CppIndexingSupport() = 0;
 
-    virtual QFuture<void> refreshSourceFiles(const QStringList &sourceFiles,
+    virtual QFuture<void> refreshSourceFiles(const QSet<QString> &sourceFiles,
         CppModelManagerInterface::ProgressNotificationMode mode) = 0;
     virtual SymbolSearcher *createSymbolSearcher(SymbolSearcher::Parameters parameters,
                                                  QSet<QString> fileNames) = 0;
diff --git a/src/plugins/cpptools/cppmodelmanager.cpp b/src/plugins/cpptools/cppmodelmanager.cpp
index 3ca1f734d089f0f91bb6037671758867b6e6354d..84d05ca108fa4c441ee9a422201d58f08322309f 100644
--- a/src/plugins/cpptools/cppmodelmanager.cpp
+++ b/src/plugins/cpptools/cppmodelmanager.cpp
@@ -141,9 +141,9 @@ static const char pp_configuration[] =
     "#define __inline inline\n"
     "#define __forceinline inline\n";
 
-QStringList CppModelManager::timeStampModifiedFiles(const QList<Document::Ptr> &documentsToCheck)
+QSet<QString> CppModelManager::timeStampModifiedFiles(const QList<Document::Ptr> &documentsToCheck)
 {
-    QStringList sourceFiles;
+    QSet<QString> sourceFiles;
 
     foreach (const Document::Ptr doc, documentsToCheck) {
         const QDateTime lastModified = doc->lastModified();
@@ -152,7 +152,7 @@ QStringList CppModelManager::timeStampModifiedFiles(const QList<Document::Ptr> &
             QFileInfo fileInfo(doc->fileName());
 
             if (fileInfo.exists() && fileInfo.lastModified() != lastModified)
-                sourceFiles.append(doc->fileName());
+                sourceFiles.insert(doc->fileName());
         }
     }
 
@@ -184,8 +184,7 @@ void CppModelManager::updateModifiedSourceFiles()
     foreach (const Document::Ptr document, snapshot)
         documentsToCheck << document;
 
-    const QStringList filesToUpdate = timeStampModifiedFiles(documentsToCheck);
-    updateSourceFiles(filesToUpdate);
+    updateSourceFiles(timeStampModifiedFiles(documentsToCheck));
 }
 
 /*!
@@ -224,7 +223,7 @@ CppModelManager::CppModelManager(QObject *parent)
             this, SIGNAL(globalSnapshotChanged()));
     connect(this, SIGNAL(aboutToRemoveFiles(QStringList)),
             this, SIGNAL(globalSnapshotChanged()));
-    connect(this, SIGNAL(sourceFilesRefreshed(QStringList)),
+    connect(this, SIGNAL(sourceFilesRefreshed(QSet<QString>)),
             this, SLOT(onSourceFilesRefreshed()));
 
     m_findReferences = new CppFindReferences(this);
@@ -505,7 +504,7 @@ QByteArray CppModelManager::codeModelConfiguration() const
     return QByteArray::fromRawData(pp_configuration, qstrlen(pp_configuration));
 }
 
-QFuture<void> CppModelManager::updateSourceFiles(const QStringList &sourceFiles,
+QFuture<void> CppModelManager::updateSourceFiles(const QSet<QString> &sourceFiles,
                                                  ProgressNotificationMode mode)
 {
     if (sourceFiles.isEmpty() || !m_indexerEnabled)
@@ -565,9 +564,9 @@ public:
     ProjectInfoComparer(const ProjectInfo &oldProjectInfo,
                         const ProjectInfo &newProjectInfo)
         : m_old(oldProjectInfo)
-        , m_oldSourceFiles(oldProjectInfo.sourceFiles().toSet())
+        , m_oldSourceFiles(oldProjectInfo.sourceFiles())
         , m_new(newProjectInfo)
-        , m_newSourceFiles(newProjectInfo.sourceFiles().toSet())
+        , m_newSourceFiles(newProjectInfo.sourceFiles())
     {}
 
     bool definesChanged() const
@@ -614,7 +613,7 @@ public:
                 documentsToCheck << document;
         }
 
-        return CppModelManager::timeStampModifiedFiles(documentsToCheck).toSet();
+        return CppModelManager::timeStampModifiedFiles(documentsToCheck);
     }
 
 private:
@@ -645,14 +644,14 @@ QFuture<void> CppModelManager::updateProjectInfo(const ProjectInfo &newProjectIn
     if (!newProjectInfo.isValid())
         return QFuture<void>();
 
-    QStringList filesToReindex;
+    QSet<QString> filesToReindex;
     bool filesRemoved = false;
 
     { // Only hold the mutex for a limited scope, so the dumping afterwards does not deadlock.
         QMutexLocker projectLocker(&m_projectMutex);
 
         ProjectExplorer::Project *project = newProjectInfo.project().data();
-        const QStringList newSourceFiles = newProjectInfo.sourceFiles();
+        const QSet<QString> newSourceFiles = newProjectInfo.sourceFiles();
 
         // Check if we can avoid a full reindexing
         ProjectInfo oldProjectInfo = m_projectToProjectsInfo.value(project);
@@ -664,7 +663,7 @@ QFuture<void> CppModelManager::updateProjectInfo(const ProjectInfo &newProjectIn
             // If the project configuration changed, do a full reindexing
             if (comparer.configurationChanged()) {
                 removeProjectInfoFilesAndIncludesFromSnapshot(oldProjectInfo);
-                filesToReindex << newSourceFiles;
+                filesToReindex.unite(newSourceFiles);
 
                 // The "configuration file" includes all defines and therefore should be updated
                 if (comparer.definesChanged()) {
@@ -675,10 +674,10 @@ QFuture<void> CppModelManager::updateProjectInfo(const ProjectInfo &newProjectIn
             // Otherwise check for added and modified files
             } else {
                 const QSet<QString> addedFiles = comparer.addedFiles();
-                filesToReindex << addedFiles.toList();
+                filesToReindex.unite(addedFiles);
 
                 const QSet<QString> modifiedFiles = comparer.timeStampModifiedFiles(snapshot());
-                filesToReindex << modifiedFiles.toList();
+                filesToReindex.unite(modifiedFiles);
             }
 
             // Announce and purge the removed files from the snapshot
@@ -691,7 +690,7 @@ QFuture<void> CppModelManager::updateProjectInfo(const ProjectInfo &newProjectIn
 
         // A new project was opened/created, do a full indexing
         } else {
-            filesToReindex << newSourceFiles;
+            filesToReindex.unite(newSourceFiles);
         }
 
         // Update Project/ProjectInfo and File/ProjectPart table
@@ -872,7 +871,7 @@ void CppModelManager::GC()
     emit gcFinished();
 }
 
-void CppModelManager::finishedRefreshingSourceFiles(const QStringList &files)
+void CppModelManager::finishedRefreshingSourceFiles(const QSet<QString> &files)
 {
     emit sourceFilesRefreshed(files);
 }
diff --git a/src/plugins/cpptools/cppmodelmanager.h b/src/plugins/cpptools/cppmodelmanager.h
index 490c9f803b216c1170887429edb1782a75933103..c748fe6e4253d67cc5e4bd074c811d2856d9e00a 100644
--- a/src/plugins/cpptools/cppmodelmanager.h
+++ b/src/plugins/cpptools/cppmodelmanager.h
@@ -62,7 +62,7 @@ public:
 
     static CppModelManager *instance();
 
-    virtual QFuture<void> updateSourceFiles(const QStringList &sourceFiles,
+    virtual QFuture<void> updateSourceFiles(const QSet<QString> &sourceFiles,
         ProgressNotificationMode mode = ReservedProgressNotification);
     virtual WorkingCopy workingCopy() const;
     virtual QByteArray codeModelConfiguration() const;
@@ -106,7 +106,7 @@ public:
     virtual void findMacroUsages(const CPlusPlus::Macro &macro);
     virtual void renameMacroUsages(const CPlusPlus::Macro &macro, const QString &replacement);
 
-    virtual void finishedRefreshingSourceFiles(const QStringList &files);
+    virtual void finishedRefreshingSourceFiles(const QSet<QString> &files);
 
     virtual void addModelManagerSupport(ModelManagerSupport *modelManagerSupport);
     virtual ModelManagerSupport *modelManagerSupportForMimeType(const QString &mimeType) const;
@@ -143,7 +143,7 @@ public:
 
     void enableGarbageCollector(bool enable);
 
-    static QStringList timeStampModifiedFiles(const QList<Document::Ptr> &documentsToCheck);
+    static QSet<QString> timeStampModifiedFiles(const QList<Document::Ptr> &documentsToCheck);
 
     static CppSourceProcessor *createSourceProcessor();
 
diff --git a/src/plugins/cpptools/cppmodelmanager_test.cpp b/src/plugins/cpptools/cppmodelmanager_test.cpp
index 0d91e6798b79a441d6d627c235bb24974b6a72e9..1cebc411a435597d27e8fb8c39917b87ce92dde3 100644
--- a/src/plugins/cpptools/cppmodelmanager_test.cpp
+++ b/src/plugins/cpptools/cppmodelmanager_test.cpp
@@ -194,7 +194,7 @@ private:
     const QString &m_filePath;
 };
 
-static QStringList updateProjectInfo(CppModelManager *modelManager, ModelManagerTestHelper *helper,
+static QSet<QString> updateProjectInfo(CppModelManager *modelManager, ModelManagerTestHelper *helper,
                                      const ProjectInfo &projectInfo)
 {
     helper->resetRefreshedSourceFiles();
@@ -315,7 +315,7 @@ void CppToolsPlugin::test_modelmanager_refresh_also_includes_of_project_files()
     part->files.append(ProjectFile(testCpp, ProjectFile::CXXSource));
     pi.appendProjectPart(part);
 
-    QStringList refreshedFiles = updateProjectInfo(mm, &helper, pi);
+    QSet<QString> refreshedFiles = updateProjectInfo(mm, &helper, pi);
     QCOMPARE(refreshedFiles.size(), 1);
     QVERIFY(refreshedFiles.contains(testCpp));
     CPlusPlus::Snapshot snapshot = mm->snapshot();
@@ -375,7 +375,7 @@ void CppToolsPlugin::test_modelmanager_refresh_several_times()
     mm->updateProjectInfo(pi);
 
     CPlusPlus::Snapshot snapshot;
-    QStringList refreshedFiles;
+    QSet<QString> refreshedFiles;
     CPlusPlus::Document::Ptr document;
 
     QByteArray defines = "#define FIRST_DEFINE";
@@ -441,7 +441,7 @@ void CppToolsPlugin::test_modelmanager_refresh_test_for_changes()
     QFuture<void> firstFuture = mm->updateProjectInfo(pi);
     QVERIFY(firstFuture.isStarted() || firstFuture.isRunning());
     firstFuture.waitForFinished();
-    const QStringList refreshedFiles = helper.waitForRefreshedSourceFiles();
+    const QSet<QString> refreshedFiles = helper.waitForRefreshedSourceFiles();
     QCOMPARE(refreshedFiles.size(), 1);
     QVERIFY(refreshedFiles.contains(testCpp));
 
@@ -475,7 +475,7 @@ void CppToolsPlugin::test_modelmanager_refresh_added_and_purge_removed()
     pi.appendProjectPart(part);
 
     CPlusPlus::Snapshot snapshot;
-    QStringList refreshedFiles;
+    QSet<QString> refreshedFiles;
 
     refreshedFiles = updateProjectInfo(mm, &helper, pi);
 
@@ -533,7 +533,7 @@ void CppToolsPlugin::test_modelmanager_refresh_timeStampModified_if_sourcefiles_
 
     Document::Ptr document;
     CPlusPlus::Snapshot snapshot;
-    QStringList refreshedFiles;
+    QSet<QString> refreshedFiles;
 
     refreshedFiles = updateProjectInfo(mm, &helper, pi);
 
@@ -608,7 +608,7 @@ void CppToolsPlugin::test_modelmanager_refresh_timeStampModified_if_sourcefiles_
 ///        files of the first project.
 void CppToolsPlugin::test_modelmanager_snapshot_after_two_projects()
 {
-    QStringList refreshedFiles;
+    QSet<QString> refreshedFiles;
     ModelManagerTestHelper helper;
     ProjectCreator project1(&helper);
     ProjectCreator project2(&helper);
@@ -622,7 +622,7 @@ void CppToolsPlugin::test_modelmanager_snapshot_after_two_projects()
                                   << _("main.cpp"));
 
     refreshedFiles = updateProjectInfo(mm, &helper, project1.projectInfo);
-    QCOMPARE(refreshedFiles.toSet(), project1.projectFiles.toSet());
+    QCOMPARE(refreshedFiles, project1.projectFiles.toSet());
     const int snapshotSizeAfterProject1 = mm->snapshot().size();
 
     foreach (const QString &file, project1.projectFiles)
@@ -636,7 +636,7 @@ void CppToolsPlugin::test_modelmanager_snapshot_after_two_projects()
                                   << _("main.cpp"));
 
     refreshedFiles = updateProjectInfo(mm, &helper, project2.projectInfo);
-    QCOMPARE(refreshedFiles.toSet(), project2.projectFiles.toSet());
+    QCOMPARE(refreshedFiles, project2.projectFiles.toSet());
 
     const int snapshotSizeAfterProject2 = mm->snapshot().size();
     QVERIFY(snapshotSizeAfterProject2 > snapshotSizeAfterProject1);
diff --git a/src/plugins/cpptools/cppmodelmanagerinterface.h b/src/plugins/cpptools/cppmodelmanagerinterface.h
index f48950499fea95da70244be2dbe297a0fff471d9..e68caee78fc6523f6d5422fe7bbb7791615a105b 100644
--- a/src/plugins/cpptools/cppmodelmanagerinterface.h
+++ b/src/plugins/cpptools/cppmodelmanagerinterface.h
@@ -110,7 +110,7 @@ public:
     virtual void renameMacroUsages(const CPlusPlus::Macro &macro, const QString &replacement = QString()) = 0;
     virtual void findMacroUsages(const CPlusPlus::Macro &macro) = 0;
 
-    virtual void finishedRefreshingSourceFiles(const QStringList &files) = 0;
+    virtual void finishedRefreshingSourceFiles(const QSet<QString> &files) = 0;
 
     virtual void addModelManagerSupport(ModelManagerSupport *modelManagerSupport) = 0;
     virtual ModelManagerSupport *modelManagerSupportForMimeType(const QString &mimeType) const = 0;
@@ -132,7 +132,7 @@ signals:
     void aboutToRemoveFiles(const QStringList &files);
 
     void documentUpdated(CPlusPlus::Document::Ptr doc);
-    void sourceFilesRefreshed(const QStringList &files);
+    void sourceFilesRefreshed(const QSet<QString> &files);
 
     /// \brief Emitted after updateProjectInfo function is called on the model-manager.
     ///
@@ -143,7 +143,7 @@ signals:
 
 public slots:
     // Documented in source file.
-    virtual QFuture<void> updateSourceFiles(const QStringList &sourceFiles,
+    virtual QFuture<void> updateSourceFiles(const QSet<QString> &sourceFiles,
         ProgressNotificationMode mode = ReservedProgressNotification) = 0;
 
     virtual void updateModifiedSourceFiles() = 0;
diff --git a/src/plugins/cpptools/cppprojects.cpp b/src/plugins/cpptools/cppprojects.cpp
index 6554e4e66794091900885842dde92f0bd7eee258..eb99b11626d5ab3d57ae7b16dc6c68d072483124 100644
--- a/src/plugins/cpptools/cppprojects.cpp
+++ b/src/plugins/cpptools/cppprojects.cpp
@@ -183,10 +183,8 @@ void ProjectInfo::appendProjectPart(const ProjectPart::Ptr &part)
     }
 
     // Update source files
-    QSet<QString> srcs = QSet<QString>::fromList(m_sourceFiles);
     foreach (const ProjectFile &file, part->files)
-        srcs.insert(file.path);
-    m_sourceFiles = srcs.toList();
+        m_sourceFiles.insert(file.path);
 
     // Update defines
     if (!m_defines.isEmpty())
@@ -213,7 +211,7 @@ const ProjectPart::HeaderPaths ProjectInfo::headerPaths() const
     return m_headerPaths;
 }
 
-const QStringList ProjectInfo::sourceFiles() const
+const QSet<QString> ProjectInfo::sourceFiles() const
 {
     return m_sourceFiles;
 }
diff --git a/src/plugins/cpptools/cppprojects.h b/src/plugins/cpptools/cppprojects.h
index 88f3241ce3bdfb6e38100ec823db67d42488d3bf..056790b113e78ed4c49ba740172cb05497308df9 100644
--- a/src/plugins/cpptools/cppprojects.h
+++ b/src/plugins/cpptools/cppprojects.h
@@ -38,6 +38,7 @@
 #include <projectexplorer/toolchain.h>
 
 #include <QPointer>
+#include <QSet>
 
 namespace CppTools {
 
@@ -148,7 +149,7 @@ public:
     void clearProjectParts();
 
     const ProjectPart::HeaderPaths headerPaths() const;
-    const QStringList sourceFiles() const;
+    const QSet<QString> sourceFiles() const;
     const QByteArray defines() const;
 
 private:
@@ -156,7 +157,7 @@ private:
     QList<ProjectPart::Ptr> m_projectParts;
     // The members below are (re)calculated from the project parts once a part is appended.
     ProjectPart::HeaderPaths m_headerPaths;
-    QStringList m_sourceFiles;
+    QSet<QString> m_sourceFiles;
     QByteArray m_defines;
 };
 
diff --git a/src/plugins/cpptools/cpprefactoringchanges.cpp b/src/plugins/cpptools/cpprefactoringchanges.cpp
index 64d4a1f77dd499d07470255c597db10d30d2e4f9..3a1f06465a09b426a4f6f408e5c0bcc2daf0cec9 100644
--- a/src/plugins/cpptools/cpprefactoringchanges.cpp
+++ b/src/plugins/cpptools/cpprefactoringchanges.cpp
@@ -74,7 +74,7 @@ public:
 
     virtual void fileChanged(const QString &fileName)
     {
-        m_modelManager->updateSourceFiles(QStringList(fileName));
+        m_modelManager->updateSourceFiles(QSet<QString>() << fileName);
     }
 
     Snapshot m_snapshot;
diff --git a/src/plugins/cpptools/cppsourceprocessor.cpp b/src/plugins/cpptools/cppsourceprocessor.cpp
index 92d0597a87854bd5fcd7f5c60e48187e57d0f17c..6e6f0147b4f8336e31ac3130357580cf8dfe15aa 100644
--- a/src/plugins/cpptools/cppsourceprocessor.cpp
+++ b/src/plugins/cpptools/cppsourceprocessor.cpp
@@ -174,8 +174,10 @@ void CppSourceProcessor::addFrameworkPath(const ProjectPart::HeaderPath &framewo
     }
 }
 
-void CppSourceProcessor::setTodo(const QStringList &files)
-{ m_todo = QSet<QString>::fromList(files); }
+void CppSourceProcessor::setTodo(const QSet<QString> &files)
+{
+    m_todo = files;
+}
 
 void CppSourceProcessor::run(const QString &fileName,
                              const QStringList &initialIncludes)
diff --git a/src/plugins/cpptools/cppsourceprocessor.h b/src/plugins/cpptools/cppsourceprocessor.h
index d2312defa43f1bf822382e078f3e99e96365ac88..e503bd5b16ddeaad95bde554a26f9145690987ae 100644
--- a/src/plugins/cpptools/cppsourceprocessor.h
+++ b/src/plugins/cpptools/cppsourceprocessor.h
@@ -71,7 +71,7 @@ public:
     void setRevision(unsigned revision);
     void setWorkingCopy(const CppTools::WorkingCopy &workingCopy);
     void setHeaderPaths(const ProjectPart::HeaderPaths &headerPaths);
-    void setTodo(const QStringList &files);
+    void setTodo(const QSet<QString> &files);
 
     void run(const QString &fileName, const QStringList &initialIncludes = QStringList());
     void removeFromCache(const QString &fileName);
diff --git a/src/plugins/cpptools/cppsourceprocessor_test.cpp b/src/plugins/cpptools/cppsourceprocessor_test.cpp
index 9b145949544642f173329d7e64403717d31827fc..9be1d9848be2f498009261554c8f44dd54f63093 100644
--- a/src/plugins/cpptools/cppsourceprocessor_test.cpp
+++ b/src/plugins/cpptools/cppsourceprocessor_test.cpp
@@ -129,7 +129,7 @@ void CppToolsPlugin::test_cppsourceprocessor_includes_cyclic()
 {
     const QString fileName1 = TestIncludePaths::testFilePath(QLatin1String("cyclic1.h"));
     const QString fileName2 = TestIncludePaths::testFilePath(QLatin1String("cyclic2.h"));
-    const QStringList sourceFiles = QStringList() << fileName1 << fileName2;
+    const QSet<QString> sourceFiles = QSet<QString>() << fileName1 << fileName2;
 
     // Create global snapshot (needed in BuiltinEditorDocumentParser)
     TestCase testCase;
diff --git a/src/plugins/cpptools/cpptoolsplugin.cpp b/src/plugins/cpptools/cpptoolsplugin.cpp
index 06007a345a731477d54209cd320f9dfed1d6eb32..debda7972c19dcdb984684b3e1bbf49adb8a8861 100644
--- a/src/plugins/cpptools/cpptoolsplugin.cpp
+++ b/src/plugins/cpptools/cpptoolsplugin.cpp
@@ -139,8 +139,10 @@ bool CppToolsPlugin::initialize(const QStringList &arguments, QString *error)
     CppModelManager *modelManager = CppModelManager::instance();
     connect(VcsManager::instance(), SIGNAL(repositoryChanged(QString)),
             modelManager, SLOT(updateModifiedSourceFiles()));
-    connect(DocumentManager::instance(), SIGNAL(filesChangedInternally(QStringList)),
-            modelManager, SLOT(updateSourceFiles(QStringList)));
+    connect(DocumentManager::instance(), &DocumentManager::filesChangedInternally,
+            [=](const QStringList &files) {
+        modelManager->updateSourceFiles(files.toSet());
+    });
 
     CppLocatorData *locatorData = new CppLocatorData;
     connect(modelManager, SIGNAL(documentUpdated(CPlusPlus::Document::Ptr)),
diff --git a/src/plugins/cpptools/cpptoolstestcase.cpp b/src/plugins/cpptools/cpptoolstestcase.cpp
index 554a993596f4bc4ddec0d860ccb36831f5f82652..c91451d179b93a4254a9ce9a3804734929d9e1f8 100644
--- a/src/plugins/cpptools/cpptoolstestcase.cpp
+++ b/src/plugins/cpptools/cpptoolstestcase.cpp
@@ -45,7 +45,7 @@ static bool closeEditorsWithoutGarbageCollectorInvocation(const QList<Core::IEdi
     return closeEditorsSucceeded;
 }
 
-static bool snapshotContains(const CPlusPlus::Snapshot &snapshot, const QStringList &filePaths)
+static bool snapshotContains(const CPlusPlus::Snapshot &snapshot, const QSet<QString> &filePaths)
 {
     foreach (const QString &filePath, filePaths) {
         if (!snapshot.contains(filePath)) {
@@ -125,7 +125,7 @@ bool TestCase::garbageCollectGlobalSnapshot()
     return globalSnapshot().isEmpty();
 }
 
-bool TestCase::parseFiles(const QStringList &filePaths)
+bool TestCase::parseFiles(const QSet<QString> &filePaths)
 {
     CppModelManagerInterface::instance()->updateSourceFiles(filePaths).waitForFinished();
     QCoreApplication::processEvents();
@@ -143,7 +143,7 @@ bool TestCase::parseFiles(const QStringList &filePaths)
 
 bool TestCase::parseFiles(const QString &filePath)
 {
-    return parseFiles(QStringList(filePath));
+    return parseFiles(QSet<QString>() << filePath);
 }
 
 void TestCase::closeEditorAtEndOfTestCase(Core::IEditor *editor)
diff --git a/src/plugins/cpptools/cpptoolstestcase.h b/src/plugins/cpptools/cpptoolstestcase.h
index c80438122dafb5dcfa3ac7f23cbe8a4e733cf6df..c222aa506c8c0587ce16c4a41eba51e6bdc0170e 100644
--- a/src/plugins/cpptools/cpptoolstestcase.h
+++ b/src/plugins/cpptools/cpptoolstestcase.h
@@ -76,7 +76,7 @@ public:
     static bool closeEditorWithoutGarbageCollectorInvocation(Core::IEditor *editor);
 
     static bool parseFiles(const QString &filePath);
-    static bool parseFiles(const QStringList &filePaths);
+    static bool parseFiles(const QSet<QString> &filePaths);
 
     static CPlusPlus::Snapshot globalSnapshot();
     static bool garbageCollectGlobalSnapshot();
diff --git a/src/plugins/cpptools/modelmanagertesthelper.cpp b/src/plugins/cpptools/modelmanagertesthelper.cpp
index 571a72c785b327690b40a663c693406c16007b46..43896781b17fa470d32b6572386886b670ac4fe9 100644
--- a/src/plugins/cpptools/modelmanagertesthelper.cpp
+++ b/src/plugins/cpptools/modelmanagertesthelper.cpp
@@ -55,9 +55,12 @@ ModelManagerTestHelper::ModelManagerTestHelper(QObject *parent) :
     CppModelManager *mm = CppModelManager::instance();
     assert(mm);
 
-    connect(this, SIGNAL(aboutToRemoveProject(ProjectExplorer::Project*)), mm, SLOT(onAboutToRemoveProject(ProjectExplorer::Project*)));
-    connect(this, SIGNAL(projectAdded(ProjectExplorer::Project*)), mm, SLOT(onProjectAdded(ProjectExplorer::Project*)));
-    connect(mm, SIGNAL(sourceFilesRefreshed(QStringList)), this, SLOT(sourceFilesRefreshed(QStringList)));
+    connect(this, SIGNAL(aboutToRemoveProject(ProjectExplorer::Project*)),
+            mm, SLOT(onAboutToRemoveProject(ProjectExplorer::Project*)));
+    connect(this, SIGNAL(projectAdded(ProjectExplorer::Project*)),
+            mm, SLOT(onProjectAdded(ProjectExplorer::Project*)));
+    connect(mm, SIGNAL(sourceFilesRefreshed(QSet<QString>)),
+            this, SLOT(sourceFilesRefreshed(QSet<QString>)));
     connect(mm, SIGNAL(gcFinished()), this, SLOT(gcFinished()));
 
     cleanup();
@@ -110,7 +113,7 @@ void ModelManagerTestHelper::resetRefreshedSourceFiles()
     m_refreshHappened = false;
 }
 
-QStringList ModelManagerTestHelper::waitForRefreshedSourceFiles()
+QSet<QString> ModelManagerTestHelper::waitForRefreshedSourceFiles()
 {
     while (!m_refreshHappened)
         QCoreApplication::processEvents();
@@ -126,7 +129,7 @@ void ModelManagerTestHelper::waitForFinishedGc()
         QCoreApplication::processEvents();
 }
 
-void ModelManagerTestHelper::sourceFilesRefreshed(const QStringList &files)
+void ModelManagerTestHelper::sourceFilesRefreshed(const QSet<QString> &files)
 {
     m_lastRefreshedSourceFiles = files;
     m_refreshHappened = true;
diff --git a/src/plugins/cpptools/modelmanagertesthelper.h b/src/plugins/cpptools/modelmanagertesthelper.h
index fdc1e449ee48119e7ce8744597e3fe0d112541be..f3bd2dd8790430c4288cd7b8363b795d0a387d90 100644
--- a/src/plugins/cpptools/modelmanagertesthelper.h
+++ b/src/plugins/cpptools/modelmanagertesthelper.h
@@ -80,7 +80,7 @@ public:
     Project *createProject(const QString &name);
 
     void resetRefreshedSourceFiles();
-    QStringList waitForRefreshedSourceFiles();
+    QSet<QString> waitForRefreshedSourceFiles();
     void waitForFinishedGc();
 
 signals:
@@ -88,13 +88,13 @@ signals:
     void projectAdded(ProjectExplorer::Project*);
 
 public slots:
-    void sourceFilesRefreshed(const QStringList &files);
+    void sourceFilesRefreshed(const QSet<QString> &files);
     void gcFinished();
 
 private:
     bool m_gcFinished;
     bool m_refreshHappened;
-    QStringList m_lastRefreshedSourceFiles;
+    QSet<QString> m_lastRefreshedSourceFiles;
 };
 
 } // namespace Internal
diff --git a/src/plugins/cpptools/typehierarchybuilder_test.cpp b/src/plugins/cpptools/typehierarchybuilder_test.cpp
index a96e3224546e75bfa4932e21d5c801980c6b5d7a..0a933dd8b99aa29cd7de2c77f95bbfa4debcc2d4 100644
--- a/src/plugins/cpptools/typehierarchybuilder_test.cpp
+++ b/src/plugins/cpptools/typehierarchybuilder_test.cpp
@@ -103,7 +103,7 @@ public:
         QVERIFY(succeededSoFar());
 
         // Write files
-        QStringList filePaths;
+        QSet<QString> filePaths;
         foreach (const Tests::TestDocument &document, documents) {
             QVERIFY(document.writeToDisk());
             filePaths << document.filePath();
@@ -114,7 +114,7 @@ public:
         const Snapshot snapshot = globalSnapshot();
 
         // Get class for which to generate the hierarchy
-        const Document::Ptr firstDocument = snapshot.document(filePaths.first());
+        const Document::Ptr firstDocument = snapshot.document(documents.first().filePath());
         QVERIFY(firstDocument);
         QVERIFY(firstDocument->diagnosticMessages().isEmpty());
         Class *clazz = FindFirstClassInDocument()(firstDocument);
diff --git a/src/plugins/genericprojectmanager/cppmodelmanagerhelper.cpp b/src/plugins/genericprojectmanager/cppmodelmanagerhelper.cpp
index 33621345b22a25f224110bd80f39b103c25ae86d..c645837865df6d8e8c8a6c983d5a6043205d55eb 100644
--- a/src/plugins/genericprojectmanager/cppmodelmanagerhelper.cpp
+++ b/src/plugins/genericprojectmanager/cppmodelmanagerhelper.cpp
@@ -40,8 +40,8 @@ using namespace GenericProjectManager::Internal::Tests;
 CppModelManagerHelper::CppModelManagerHelper(QObject *parent) :
     QObject(parent)
 {
-    connect(cppModelManager(), SIGNAL(sourceFilesRefreshed(const QStringList &)),
-            this, SLOT(onSourceFilesRefreshed(const QStringList &)));
+    connect(cppModelManager(), SIGNAL(sourceFilesRefreshed(const QSet<QString> &)),
+            this, SLOT(onSourceFilesRefreshed(const QSet<QString> &)));
 }
 
 
@@ -59,7 +59,7 @@ void CppModelManagerHelper::waitForSourceFilesRefreshed(const QStringList &files
 {
     QTime t;
     t.start();
-    QSignalSpy spy(cppModelManager(), SIGNAL(sourceFilesRefreshed(const QStringList &)));
+    QSignalSpy spy(cppModelManager(), SIGNAL(sourceFilesRefreshed(const QSet<QString> &)));
 
     foreach (const QString &file, files) {
         while (!m_refreshedSourceFiles.contains(file)) {
@@ -83,7 +83,7 @@ void CppModelManagerHelper::waitForSourceFilesRefreshed(const QStringList &files
     }
 }
 
-void CppModelManagerHelper::onSourceFilesRefreshed(const QStringList &files)
+void CppModelManagerHelper::onSourceFilesRefreshed(const QSet<QString> &files)
 {
-    m_refreshedSourceFiles += files;
+    m_refreshedSourceFiles.unite(files);
 }
diff --git a/src/plugins/genericprojectmanager/cppmodelmanagerhelper.h b/src/plugins/genericprojectmanager/cppmodelmanagerhelper.h
index e854c73c8834ccbd7521463751763821ac22ae11..d5e2c4d4f6b809b6f81579a78de0cd2ad911ae02 100644
--- a/src/plugins/genericprojectmanager/cppmodelmanagerhelper.h
+++ b/src/plugins/genericprojectmanager/cppmodelmanagerhelper.h
@@ -51,10 +51,10 @@ public:
     void waitForSourceFilesRefreshed(const QStringList &files, int timeOut = defaultTimeOut);
 
 private slots:
-    void onSourceFilesRefreshed(const QStringList &files);
+    void onSourceFilesRefreshed(const QSet<QString> &files);
 
 private:
-    QStringList m_refreshedSourceFiles;
+    QSet<QString> m_refreshedSourceFiles;
 };
 
 } // Tests namespace
diff --git a/src/plugins/todo/cpptodoitemsscanner.cpp b/src/plugins/todo/cpptodoitemsscanner.cpp
index b001edc5ff57990d9218c38053fa59bbb4b0005a..ce938b10fd5c5fa1daa9b1d71fb68159a718e485 100644
--- a/src/plugins/todo/cpptodoitemsscanner.cpp
+++ b/src/plugins/todo/cpptodoitemsscanner.cpp
@@ -52,9 +52,9 @@ void CppTodoItemsScanner::keywordListChanged()
 
     CppTools::CppModelManagerInterface *modelManager = CppTools::CppModelManagerInterface::instance();
 
-    QStringList filesToBeUpdated;
+    QSet<QString> filesToBeUpdated;
     foreach (const CppTools::ProjectInfo &info, modelManager->projectInfos())
-        filesToBeUpdated << info.project().data()->files(ProjectExplorer::Project::ExcludeGeneratedFiles);
+        filesToBeUpdated.unite(info.project().data()->files(ProjectExplorer::Project::ExcludeGeneratedFiles).toSet());
 
     modelManager->updateSourceFiles(filesToBeUpdated);
 }