diff --git a/cmake/compileroptions.cmake b/cmake/compileroptions.cmake
index 829ce3a6d..1021707a2 100644
--- a/cmake/compileroptions.cmake
+++ b/cmake/compileroptions.cmake
@@ -1,3 +1,12 @@
+include(CheckCXXCompilerFlag)
+
+function(add_compile_options_safe FLAG)
+    check_cxx_compiler_flag(${FLAG} _has_flag)
+    if (_has_flag)
+        add_compile_options(${FLAG})
+    endif()
+endfunction()
+
 if (CMAKE_CXX_COMPILER_ID MATCHES "GNU" OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     if(CMAKE_BUILD_TYPE MATCHES "Release")
         # "Release" uses -O3 by default
@@ -6,20 +15,15 @@ if (CMAKE_CXX_COMPILER_ID MATCHES "GNU" OR CMAKE_CXX_COMPILER_ID MATCHES "Clang"
     if (WARNINGS_ARE_ERRORS)
         add_compile_options(-Werror)
     endif()
-endif()
-
-if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
-    if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.6)
-        message(FATAL_ERROR "${PROJECT_NAME} c++11 support requires g++ 4.6 or greater, but it is ${CMAKE_CXX_COMPILER_VERSION}")
-    endif ()
-
+    add_compile_options(-pedantic)
+    add_compile_options(-Wall)
+    add_compile_options(-Wextra)
     add_compile_options(-Wcast-qual)                # Cast for removing type qualifiers
     add_compile_options(-Wno-deprecated-declarations)
     add_compile_options(-Wfloat-equal)              # Floating values used in equality comparisons
     add_compile_options(-Wmissing-declarations)     # If a global function is defined without a previous declaration
     add_compile_options(-Wmissing-format-attribute) #
     add_compile_options(-Wno-long-long)
-    add_compile_options(-Woverloaded-virtual)       # when a function declaration hides virtual functions from a base class
     add_compile_options(-Wpacked)                   #
     add_compile_options(-Wredundant-decls)          # if anything is declared more than once in the same scope
     add_compile_options(-Wundef)
@@ -28,22 +32,24 @@ if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
     add_compile_options(-Wno-missing-braces)
     add_compile_options(-Wno-sign-compare)
     add_compile_options(-Wno-multichar)
+endif()
+
+if (CMAKE_CXX_COMPILER_ID MATCHES "GNU")
+    if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.6)
+        message(FATAL_ERROR "${PROJECT_NAME} c++11 support requires g++ 4.6 or greater, but it is ${CMAKE_CXX_COMPILER_VERSION}")
+    endif ()
+
+    add_compile_options(-Woverloaded-virtual)       # when a function declaration hides virtual functions from a base class
     add_compile_options(-Wno-maybe-uninitialized)   # there are some false positives
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
 
-   add_compile_options(-Wno-deprecated-declarations)
    add_compile_options(-Wno-four-char-constants)
    add_compile_options(-Wno-missing-braces)
-   add_compile_options(-Wno-missing-field-initializers)
-   add_compile_options(-Wno-multichar)
-   add_compile_options(-Wno-sign-compare)
    add_compile_options(-Wno-unused-function)
-   if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "8.0.0")
-      add_compile_options(-Wextra-semi-stmt)
-   endif()
+   add_compile_options_safe(-Wextra-semi-stmt)
 
    if(ENABLE_COVERAGE OR ENABLE_COVERAGE_XML)
-      message(FATAL_ERROR "Not use clang for generate code coverage. Use gcc.")
+      message(FATAL_ERROR "Do not use clang for generate code coverage. Use gcc.")
    endif()
 endif()
 
diff --git a/gui/mainwindow.cpp b/gui/mainwindow.cpp
index d763d6eaf..5fd02499f 100644
--- a/gui/mainwindow.cpp
+++ b/gui/mainwindow.cpp
@@ -610,7 +610,7 @@ void MainWindow::updateFunctionContractsTab()
 {
     QStringList addedContracts;
     if (mProjectFile) {
-        for (const auto it: mProjectFile->getFunctionContracts()) {
+        for (const auto& it: mProjectFile->getFunctionContracts()) {
             addedContracts << QString::fromStdString(it.first);
         }
     }
@@ -876,7 +876,7 @@ Settings MainWindow::getCppcheckSettings()
 
         result.functionContracts = mProjectFile->getFunctionContracts();
 
-        for (const auto vc: mProjectFile->getVariableContracts())
+        for (const auto& vc: mProjectFile->getVariableContracts())
             result.variableContracts[vc.first.toStdString()] = vc.second;
 
         const QStringList undefines = mProjectFile->getUndefines();
diff --git a/gui/projectfile.cpp b/gui/projectfile.cpp
index 810f42212..926d55d0c 100644
--- a/gui/projectfile.cpp
+++ b/gui/projectfile.cpp
@@ -958,7 +958,7 @@ bool ProjectFile::write(const QString &filename)
 
     if (!mFunctionContracts.empty()) {
         xmlWriter.writeStartElement(CppcheckXml::FunctionContracts);
-        for (const auto contract: mFunctionContracts) {
+        for (const auto& contract: mFunctionContracts) {
             xmlWriter.writeStartElement(CppcheckXml::FunctionContract);
             xmlWriter.writeAttribute(CppcheckXml::ContractFunction, QString::fromStdString(contract.first));
             xmlWriter.writeAttribute(CppcheckXml::ContractExpects, QString::fromStdString(contract.second));
@@ -1025,7 +1025,7 @@ bool ProjectFile::write(const QString &filename)
     writeStringList(xmlWriter, mTags, CppcheckXml::TagsElementName, CppcheckXml::TagElementName);
     if (!mWarningTags.empty()) {
         QStringList tags;
-        for (const auto wt: mWarningTags) {
+        for (const auto& wt: mWarningTags) {
             if (!tags.contains(wt.second))
                 tags.append(wt.second);
         }
@@ -1033,7 +1033,7 @@ bool ProjectFile::write(const QString &filename)
             xmlWriter.writeStartElement(CppcheckXml::TagWarningsElementName);
             xmlWriter.writeAttribute(CppcheckXml::TagAttributeName, tag);
             QStringList warnings;
-            for (const auto wt: mWarningTags) {
+            for (const auto& wt: mWarningTags) {
                 if (wt.second == tag) {
                     xmlWriter.writeStartElement(CppcheckXml::WarningElementName);
                     xmlWriter.writeAttribute(CppcheckXml::HashAttributeName, QString::number(wt.first));
diff --git a/gui/resultsview.cpp b/gui/resultsview.cpp
index cb77e7912..6b43ee998 100644
--- a/gui/resultsview.cpp
+++ b/gui/resultsview.cpp
@@ -103,7 +103,7 @@ void ResultsView::setAddedFunctionContracts(const QStringList &addedContracts)
 {
     mUI.mListAddedContracts->clear();
     mUI.mListAddedContracts->addItems(addedContracts);
-    for (const QString f: addedContracts) {
+    for (const QString& f: addedContracts) {
         auto res = mUI.mListMissingContracts->findItems(f, Qt::MatchExactly);
         if (!res.empty())
             delete res.front();
@@ -114,7 +114,7 @@ void ResultsView::setAddedVariableContracts(const QStringList &added)
 {
     mUI.mListAddedVariables->clear();
     mUI.mListAddedVariables->addItems(added);
-    for (const QString var: added) {
+    for (const QString& var: added) {
         for (auto item: mUI.mListMissingVariables->findItems(var, Qt::MatchExactly))
             delete item;
         mVariableContracts.insert(var);