diff --git a/.clang-tidy b/.clang-tidy
index 583b06cd0..13451e0d6 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -1,5 +1,5 @@
 ---
-Checks:          '*,-abseil-*,-altera-*,-android-*,-boost-*,-cert-*,-cppcoreguidelines-*,-darwin-*,-fuchsia-*,-google-*,-hicpp-*,-linuxkernel-*,-llvm-*,-llvmlibc-*,-mpi-*,-objc-*,-openmp-*,-zircon-*,-readability-braces-around-statements,-readability-magic-numbers,-bugprone-macro-parentheses,-readability-isolate-declaration,-readability-function-size,-modernize-use-trailing-return-type,-readability-implicit-bool-conversion,-readability-uppercase-literal-suffix,-modernize-use-auto,-readability-else-after-return,-modernize-use-default-member-init,-readability-named-parameter,-readability-redundant-member-init,-performance-faster-string-find,-modernize-avoid-c-arrays,-modernize-use-equals-default,-readability-container-size-empty,-readability-simplify-boolean-expr,-bugprone-branch-clone,-bugprone-narrowing-conversions,-modernize-raw-string-literal,-readability-convert-member-functions-to-static,-modernize-loop-convert,-readability-const-return-type,-performance-unnecessary-value-param,-modernize-return-braced-init-list,-performance-inefficient-string-concatenation,-misc-throw-by-value-catch-by-reference,-readability-avoid-const-params-in-decls,-readability-non-const-parameter,-misc-non-private-member-variables-in-classes,-bugprone-suspicious-string-compare,-clang-analyzer-*,-bugprone-signed-char-misuse,-readability-make-member-function-const,-misc-no-recursion,-readability-use-anyofallof,-performance-no-automatic-move,-bugprone-suspicious-include,-modernize-replace-random-shuffle,-readability-function-cognitive-complexity,-readability-redundant-access-specifiers,-performance-noexcept-move-constructor,-concurrency-mt-unsafe,-bugprone-easily-swappable-parameters,-readability-suspicious-call-argument,-readability-identifier-length,-readability-container-data-pointer,-bugprone-assignment-in-if-condition,-misc-const-correctness'
+Checks:          '*,-abseil-*,-altera-*,-android-*,-boost-*,-cert-*,-cppcoreguidelines-*,-darwin-*,-fuchsia-*,-google-*,-hicpp-*,-linuxkernel-*,-llvm-*,-llvmlibc-*,-mpi-*,-objc-*,-openmp-*,-zircon-*,-readability-braces-around-statements,-readability-magic-numbers,-bugprone-macro-parentheses,-readability-isolate-declaration,-readability-function-size,-modernize-use-trailing-return-type,-readability-implicit-bool-conversion,-readability-uppercase-literal-suffix,-modernize-use-auto,-readability-else-after-return,-modernize-use-default-member-init,-readability-named-parameter,-readability-redundant-member-init,-performance-faster-string-find,-modernize-avoid-c-arrays,-modernize-use-equals-default,-readability-container-size-empty,-readability-simplify-boolean-expr,-bugprone-branch-clone,-bugprone-narrowing-conversions,-modernize-raw-string-literal,-readability-convert-member-functions-to-static,-modernize-loop-convert,-readability-const-return-type,-performance-unnecessary-value-param,-modernize-return-braced-init-list,-performance-inefficient-string-concatenation,-misc-throw-by-value-catch-by-reference,-readability-avoid-const-params-in-decls,-readability-non-const-parameter,-misc-non-private-member-variables-in-classes,-bugprone-suspicious-string-compare,-clang-analyzer-*,-bugprone-signed-char-misuse,-misc-no-recursion,-readability-use-anyofallof,-performance-no-automatic-move,-bugprone-suspicious-include,-modernize-replace-random-shuffle,-readability-function-cognitive-complexity,-readability-redundant-access-specifiers,-performance-noexcept-move-constructor,-concurrency-mt-unsafe,-bugprone-easily-swappable-parameters,-readability-suspicious-call-argument,-readability-identifier-length,-readability-container-data-pointer,-bugprone-assignment-in-if-condition,-misc-const-correctness'
 WarningsAsErrors: '*'
 CheckOptions:
   - key:             misc-non-private-member-variables-in-classes.IgnoreClassesWithAllMemberVariablesBeingPublic
diff --git a/cli/processexecutor.cpp b/cli/processexecutor.cpp
index 1448a0bc3..2719513a1 100644
--- a/cli/processexecutor.cpp
+++ b/cli/processexecutor.cpp
@@ -82,14 +82,14 @@ public:
         report(msg, MessageType::REPORT_INFO);
     }
 
-    void writeEnd(const std::string& str) {
+    void writeEnd(const std::string& str) const {
         writeToPipe(CHILD_END, str);
     }
 
 private:
     enum class MessageType {REPORT_ERROR, REPORT_INFO};
 
-    void report(const ErrorMessage &msg, MessageType msgType) {
+    void report(const ErrorMessage &msg, MessageType msgType) const {
         PipeSignal pipeSignal;
         switch (msgType) {
         case MessageType::REPORT_ERROR:
@@ -103,7 +103,7 @@ private:
         writeToPipe(pipeSignal, msg.serialize());
     }
 
-    void writeToPipe(PipeSignal type, const std::string &data)
+    void writeToPipe(PipeSignal type, const std::string &data) const
     {
         unsigned int len = static_cast<unsigned int>(data.length() + 1);
         char *out = new char[len + 1 + sizeof(len)];
diff --git a/gui/mainwindow.h b/gui/mainwindow.h
index 564674079..617c8187a 100644
--- a/gui/mainwindow.h
+++ b/gui/mainwindow.h
@@ -320,7 +320,7 @@ private:
     void formatAndSetTitle(const QString &text = QString());
 
     /** @brief Show help contents */
-    void openOnlineHelp();
+    static void openOnlineHelp();
 
     /**
      * @brief Enable or disable project file actions.
diff --git a/gui/projectfile.h b/gui/projectfile.h
index 92abca02a..0e60ddbb9 100644
--- a/gui/projectfile.h
+++ b/gui/projectfile.h
@@ -415,9 +415,9 @@ protected:
      */
     void readImportProject(QXmlStreamReader &reader);
 
-    bool readBool(QXmlStreamReader &reader);
+    static bool readBool(QXmlStreamReader &reader);
 
-    int readInt(QXmlStreamReader &reader, int defaultValue);
+    static int readInt(QXmlStreamReader &reader, int defaultValue);
 
     /**
      * @brief Read list of include directories from XML.
@@ -473,7 +473,7 @@ protected:
      * @param reader       XML stream reader
      * @param elementname  elementname for each string
      */
-    void readStringList(QStringList &stringlist, QXmlStreamReader &reader, const char elementname[]);
+    static void readStringList(QStringList &stringlist, QXmlStreamReader &reader, const char elementname[]);
 
     /**
      * @brief Write string list
diff --git a/gui/projectfiledialog.h b/gui/projectfiledialog.h
index 18c8deece..d7f803e8a 100644
--- a/gui/projectfiledialog.h
+++ b/gui/projectfiledialog.h
@@ -316,7 +316,7 @@ protected:
     int getSuppressionIndex(const QString &shortText) const;
 
 private:
-    QStringList getProjectConfigs(const QString &fileName);
+    static QStringList getProjectConfigs(const QString &fileName);
 
     Ui::ProjectFile *mUI;
 
diff --git a/gui/resultstree.cpp b/gui/resultstree.cpp
index b93e5685e..7eada6f4c 100644
--- a/gui/resultstree.cpp
+++ b/gui/resultstree.cpp
@@ -1156,7 +1156,7 @@ QString ResultsTree::getFilePath(QStandardItem *target, bool fullPath)
     return QString();
 }
 
-QString ResultsTree::severityToIcon(Severity::SeverityType severity) const
+QString ResultsTree::severityToIcon(Severity::SeverityType severity)
 {
     switch (severity) {
     case Severity::error:
diff --git a/gui/resultstree.h b/gui/resultstree.h
index c72c435ab..6f0c6800e 100644
--- a/gui/resultstree.h
+++ b/gui/resultstree.h
@@ -329,7 +329,7 @@ protected:
      *
      * @param severity Severity
      */
-    QString severityToIcon(Severity::SeverityType severity) const;
+    static QString severityToIcon(Severity::SeverityType severity);
 
     /**
      * @brief Helper function to open an error within target with application*
@@ -354,7 +354,7 @@ protected:
      * @param target The error tree item containing the filename/full path
      * @param fullPath Whether or not to retrieve the full path or only the filename.
      */
-    QString getFilePath(QStandardItem *target, bool fullPath);
+    static QString getFilePath(QStandardItem *target, bool fullPath);
 
     /**
      * @brief Context menu event (user right clicked on the tree)
diff --git a/gui/test/cppchecklibrarydata/testcppchecklibrarydata.h b/gui/test/cppchecklibrarydata/testcppchecklibrarydata.h
index 12a9efd5a..1073fb7ac 100644
--- a/gui/test/cppchecklibrarydata/testcppchecklibrarydata.h
+++ b/gui/test/cppchecklibrarydata/testcppchecklibrarydata.h
@@ -42,8 +42,8 @@ private slots:
     void containerValid();
 
 private:
-    void loadCfgFile(QString filename, CppcheckLibraryData &data, QString &res, bool removeFile = false);
-    void saveCfgFile(QString filename, CppcheckLibraryData &data);
+    static void loadCfgFile(QString filename, CppcheckLibraryData &data, QString &res, bool removeFile = false);
+    static void saveCfgFile(QString filename, CppcheckLibraryData &data);
 
     CppcheckLibraryData libraryData;
     CppcheckLibraryData fileLibraryData;
diff --git a/gui/test/filelist/testfilelist.cpp b/gui/test/filelist/testfilelist.cpp
index c0f25fa22..c8d48efa1 100644
--- a/gui/test/filelist/testfilelist.cpp
+++ b/gui/test/filelist/testfilelist.cpp
@@ -24,7 +24,7 @@
 #include <QString>
 #include <QTest>
 
-void TestFileList::addFile()
+void TestFileList::addFile() const
 {
     // Accepted extensions: *.cpp, *.cxx, *.cc, *.c, *.c++, *.txx, *.tpp, *.ipp, *.ixx"
     FileList list;
@@ -41,7 +41,7 @@ void TestFileList::addFile()
     QCOMPARE(files.size(), 9);
 }
 
-void TestFileList::addPathList()
+void TestFileList::addPathList() const
 {
     // Accepted extensions: *.cpp, *.cxx, *.cc, *.c, *.c++, *.txx, *.tpp, *.ipp, *.ixx"
     QStringList paths;
@@ -60,7 +60,7 @@ void TestFileList::addPathList()
     QCOMPARE(files.size(), 9);
 }
 
-void TestFileList::addFile_notexist()
+void TestFileList::addFile_notexist() const
 {
     FileList list;
     list.addFile(QString(SRCDIR) + "/../data/files/bar1.cpp");
@@ -68,7 +68,7 @@ void TestFileList::addFile_notexist()
     QCOMPARE(files.size(), 0);
 }
 
-void TestFileList::addFile_unknown()
+void TestFileList::addFile_unknown() const
 {
     FileList list;
     list.addFile(QString(SRCDIR) + "/../data/files/bar1");
@@ -77,7 +77,7 @@ void TestFileList::addFile_unknown()
     QCOMPARE(files.size(), 0);
 }
 
-void TestFileList::addDirectory()
+void TestFileList::addDirectory() const
 {
     FileList list;
     list.addDirectory(QString(SRCDIR) + "/../data/files");
@@ -85,7 +85,7 @@ void TestFileList::addDirectory()
     QCOMPARE(files.size(), 7);
 }
 
-void TestFileList::addDirectory_recursive()
+void TestFileList::addDirectory_recursive() const
 {
     FileList list;
     list.addDirectory(QString(SRCDIR) + "/../data/files", true);
@@ -98,7 +98,7 @@ void TestFileList::addDirectory_recursive()
     QVERIFY(files.contains(base + "/dir2/foo1.cpp"));
 }
 
-void TestFileList::filterFiles()
+void TestFileList::filterFiles() const
 {
     FileList list;
     QStringList filters;
@@ -121,7 +121,7 @@ void TestFileList::filterFiles()
     QVERIFY(!files.contains(base + "/foo3.cpp"));
 }
 
-void TestFileList::filterFiles2()
+void TestFileList::filterFiles2() const
 {
     FileList list;
     QStringList filters;
@@ -136,7 +136,7 @@ void TestFileList::filterFiles2()
     QVERIFY(!files.contains(base + "/foo3.cpp"));
 }
 
-void TestFileList::filterFiles3()
+void TestFileList::filterFiles3() const
 {
     FileList list;
     QStringList filters;
@@ -153,7 +153,7 @@ void TestFileList::filterFiles3()
     QVERIFY(!files.contains(base + "/dir2/foo1.cpp"));
 }
 
-void TestFileList::filterFiles4()
+void TestFileList::filterFiles4() const
 {
     FileList list;
     QStringList filters;
diff --git a/gui/test/filelist/testfilelist.h b/gui/test/filelist/testfilelist.h
index 61e579d0b..5fbc420ea 100644
--- a/gui/test/filelist/testfilelist.h
+++ b/gui/test/filelist/testfilelist.h
@@ -22,14 +22,14 @@ class TestFileList : public QObject {
     Q_OBJECT
 
 private slots:
-    void addFile();
-    void addPathList();
-    void addFile_notexist();
-    void addFile_unknown();
-    void addDirectory();
-    void addDirectory_recursive();
-    void filterFiles();
-    void filterFiles2();
-    void filterFiles3();
-    void filterFiles4();
+    void addFile() const;
+    void addPathList() const;
+    void addFile_notexist() const;
+    void addFile_unknown() const;
+    void addDirectory() const;
+    void addDirectory_recursive() const;
+    void filterFiles() const;
+    void filterFiles2() const;
+    void filterFiles3() const;
+    void filterFiles4() const;
 };
diff --git a/gui/test/projectfile/testprojectfile.cpp b/gui/test/projectfile/testprojectfile.cpp
index 52ce479c3..bcc1fc2d7 100644
--- a/gui/test/projectfile/testprojectfile.cpp
+++ b/gui/test/projectfile/testprojectfile.cpp
@@ -37,14 +37,14 @@ bool ImportProject::sourceFileExists(const std::string & /*file*/) {
     return true;
 }
 
-void TestProjectFile::loadInexisting()
+void TestProjectFile::loadInexisting() const
 {
     const QString filepath(QString(SRCDIR) + "/../data/projectfiles/foo.cppcheck");
     ProjectFile pfile(filepath);
     QCOMPARE(pfile.read(), false);
 }
 
-void TestProjectFile::loadSimple()
+void TestProjectFile::loadSimple() const
 {
     const QString filepath(QString(SRCDIR) + "/../data/projectfiles/simple.cppcheck");
     ProjectFile pfile(filepath);
@@ -67,7 +67,7 @@ void TestProjectFile::loadSimple()
 }
 
 // Test that project file with old 'ignore' element works
-void TestProjectFile::loadSimpleWithIgnore()
+void TestProjectFile::loadSimpleWithIgnore() const
 {
     const QString filepath(QString(SRCDIR) + "/../data/projectfiles/simple_ignore.cppcheck");
     ProjectFile pfile(filepath);
@@ -89,7 +89,7 @@ void TestProjectFile::loadSimpleWithIgnore()
     QCOMPARE(defines[0], QString("FOO"));
 }
 
-void TestProjectFile::loadSimpleNoroot()
+void TestProjectFile::loadSimpleNoroot() const
 {
     const QString filepath(QString(SRCDIR) + "/../data/projectfiles/simple_noroot.cppcheck");
     ProjectFile pfile(filepath);
diff --git a/gui/test/projectfile/testprojectfile.h b/gui/test/projectfile/testprojectfile.h
index ac01d5b54..762c893d7 100644
--- a/gui/test/projectfile/testprojectfile.h
+++ b/gui/test/projectfile/testprojectfile.h
@@ -22,8 +22,8 @@ class TestProjectFile : public QObject {
     Q_OBJECT
 
 private slots:
-    void loadInexisting();
-    void loadSimple();
-    void loadSimpleWithIgnore();
-    void loadSimpleNoroot();
+    void loadInexisting() const;
+    void loadSimple() const;
+    void loadSimpleWithIgnore() const;
+    void loadSimpleNoroot() const;
 };
diff --git a/gui/test/translationhandler/testtranslationhandler.cpp b/gui/test/translationhandler/testtranslationhandler.cpp
index 1ded6c297..e726970f2 100644
--- a/gui/test/translationhandler/testtranslationhandler.cpp
+++ b/gui/test/translationhandler/testtranslationhandler.cpp
@@ -31,7 +31,7 @@ static const QStringList getTranslationNames(const TranslationHandler& handler)
     return names;
 }
 
-void TestTranslationHandler::construct()
+void TestTranslationHandler::construct() const
 {
     TranslationHandler handler;
     QCOMPARE(getTranslationNames(handler).size(), 13);  // 12 translations + english
diff --git a/gui/test/translationhandler/testtranslationhandler.h b/gui/test/translationhandler/testtranslationhandler.h
index c18308b89..29f3e417f 100644
--- a/gui/test/translationhandler/testtranslationhandler.h
+++ b/gui/test/translationhandler/testtranslationhandler.h
@@ -22,5 +22,5 @@ class TestTranslationHandler : public QObject {
     Q_OBJECT
 
 private slots:
-    void construct();
+    void construct() const;
 };
diff --git a/gui/test/xmlreportv2/testxmlreportv2.cpp b/gui/test/xmlreportv2/testxmlreportv2.cpp
index 07496962d..90a273225 100644
--- a/gui/test/xmlreportv2/testxmlreportv2.cpp
+++ b/gui/test/xmlreportv2/testxmlreportv2.cpp
@@ -23,7 +23,7 @@
 
 #include <QtTest>
 
-void TestXmlReportV2::readXml()
+void TestXmlReportV2::readXml() const
 {
     const QString filepath(QString(SRCDIR) + "/../data/xmlfiles/xmlreport_v2.xml");
     XmlReportV2 report(filepath);
diff --git a/gui/test/xmlreportv2/testxmlreportv2.h b/gui/test/xmlreportv2/testxmlreportv2.h
index b78b50f4b..2afbe54fc 100644
--- a/gui/test/xmlreportv2/testxmlreportv2.h
+++ b/gui/test/xmlreportv2/testxmlreportv2.h
@@ -22,5 +22,5 @@ class TestXmlReportV2 : public QObject {
     Q_OBJECT
 
 private slots:
-    void readXml();
+    void readXml() const;
 };
diff --git a/lib/checkclass.cpp b/lib/checkclass.cpp
index 178d0c0fd..d081afb12 100644
--- a/lib/checkclass.cpp
+++ b/lib/checkclass.cpp
@@ -2893,8 +2893,8 @@ void CheckClass::overrideError(const Function *funcInBase, const Function *funcI
 
     ErrorPath errorPath;
     if (funcInBase && funcInDerived) {
-        errorPath.push_back(ErrorPathItem(funcInBase->tokenDef, "Virtual " + funcType + " in base class"));
-        errorPath.push_back(ErrorPathItem(funcInDerived->tokenDef, char(std::toupper(funcType[0])) + funcType.substr(1) + " in derived class"));
+        errorPath.emplace_back(funcInBase->tokenDef, "Virtual " + funcType + " in base class");
+        errorPath.emplace_back(funcInDerived->tokenDef, char(std::toupper(funcType[0])) + funcType.substr(1) + " in derived class");
     }
 
     reportError(errorPath, Severity::style, "missingOverride",
diff --git a/lib/clangimport.cpp b/lib/clangimport.cpp
index 1462eed72..7ece09c63 100644
--- a/lib/clangimport.cpp
+++ b/lib/clangimport.cpp
@@ -208,7 +208,7 @@ namespace clangimport {
             Decl(Token *def, Variable *var) : def(def), enumerator(nullptr), function(nullptr), scope(nullptr), var(var) {}
             Decl(Token *def, Function *function) : def(def), enumerator(nullptr), function(function), scope(nullptr), var(nullptr) {}
             Decl(Token *def, Enumerator *enumerator) : def(def), enumerator(enumerator), function(nullptr), scope(nullptr), var(nullptr) {}
-            void ref(Token *tok) {
+            void ref(Token *tok) const {
                 if (enumerator)
                     tok->enumerator(enumerator);
                 if (function)
diff --git a/lib/forwardanalyzer.cpp b/lib/forwardanalyzer.cpp
index 8a3bc6105..5435109c7 100644
--- a/lib/forwardanalyzer.cpp
+++ b/lib/forwardanalyzer.cpp
@@ -333,7 +333,7 @@ struct ForwardTraversal {
         return false;
     }
 
-    bool isEscapeScope(const Token* endBlock, bool& unknown) {
+    bool isEscapeScope(const Token* endBlock, bool& unknown) const {
         const Token* ftok = nullptr;
         bool r = isReturnScope(endBlock, &settings->library, &ftok);
         if (!r && ftok)
@@ -389,7 +389,7 @@ struct ForwardTraversal {
         return bail;
     }
 
-    bool reentersLoop(Token* endBlock, const Token* condTok, const Token* stepTok) {
+    bool reentersLoop(Token* endBlock, const Token* condTok, const Token* stepTok) const {
         if (!condTok)
             return true;
         if (Token::simpleMatch(condTok, ":"))
diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 0a58ada5a..6f8712e88 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -4407,7 +4407,7 @@ struct Lambda {
     std::unordered_map<const Variable*, std::pair<const Token*, LifetimeCapture>> explicitCaptures;
     LifetimeCapture implicitCapture;
 
-    std::vector<const Token*> getCaptures() {
+    std::vector<const Token*> getCaptures() const {
         return getArguments(capture);
     }
 
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 604033309..70ad741c8 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -534,13 +534,13 @@ private:
         return values.size() == 1U && !values.front().isTokValue() ? values.front() : ValueFlow::Value();
     }
 
-    std::list<ValueFlow::Value> removeSymbolic(std::list<ValueFlow::Value> values)
+    static std::list<ValueFlow::Value> removeSymbolic(std::list<ValueFlow::Value> values)
     {
         values.remove_if(std::mem_fn(&ValueFlow::Value::isSymbolicValue));
         return values;
     }
 
-    std::list<ValueFlow::Value> removeImpossible(std::list<ValueFlow::Value> values)
+    static std::list<ValueFlow::Value> removeImpossible(std::list<ValueFlow::Value> values)
     {
         values.remove_if(std::mem_fn(&ValueFlow::Value::isImpossible));
         return values;