diff --git a/CMakeLists.txt b/CMakeLists.txt
index 33d2d835..185e3fe5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -360,7 +360,7 @@ if(ENABLE_CPP_CORE_GUIDELINES_CHECK)
     message(WARNING "clang-tidy not found.")
   else()
     message(STATUS "clang-tidy found: ${CLANG_TIDY_EXE}")
-    set(DO_CLANG_TIDY "${CLANG_TIDY_EXE}" "-checks=*,-clang-analyzer-alpha.*,-*braces-around-statements,-fuchsia-default-arguments")
+    set(DO_CLANG_TIDY "${CLANG_TIDY_EXE}" "-warnings-as-errors=*" "-header-filter=libsrc/core/")
   endif()
 endif(ENABLE_CPP_CORE_GUIDELINES_CHECK)
 
diff --git a/libsrc/core/.clang-tidy b/libsrc/core/.clang-tidy
new file mode 100644
index 00000000..c299ae90
--- /dev/null
+++ b/libsrc/core/.clang-tidy
@@ -0,0 +1,4 @@
+Checks: '*,-clang-analyzer-alpha.*,-*braces-around-statements,-fuchsia-*,-google-runtime-references,-readability-implicit-bool-conversion'
+CheckOptions:
+        - key: cppcoreguidelines-special-member-functions.AllowSoleDefaultDtor
+          value: 1
\ No newline at end of file
diff --git a/libsrc/core/archive.hpp b/libsrc/core/archive.hpp
index 89656ad5..66589d90 100644
--- a/libsrc/core/archive.hpp
+++ b/libsrc/core/archive.hpp
@@ -3,8 +3,8 @@
 
 #include <complex>
 #include <cstring>
-#include <functional>
 #include <fstream>
+#include <functional>
 #include <iostream>
 #include <map>
 #include <memory>
@@ -25,12 +25,12 @@ namespace ngcore
   NGCORE_API std::string demangle(const char* typeinfo);
 
   // create new pointer of type T if it is default constructible, else throw
-  template<typename T>
-  T* constructIfPossible_impl(...)
+  template<typename T, typename ...Rest>
+  T* constructIfPossible_impl(Rest... /*unused*/)
   { throw std::runtime_error(std::string(demangle(typeid(T).name())) + " is not default constructible!"); }
 
   template<typename T, typename= typename std::enable_if<std::is_constructible<T>::value>::type>
-  T* constructIfPossible_impl(int) { return new T; }
+  T* constructIfPossible_impl(int /*unused*/) { return new T; }
 
   template<typename T>
   T* constructIfPossible() { return constructIfPossible_impl<T>(int{}); }
@@ -45,7 +45,7 @@ namespace ngcore
       typename std::is_same<decltype(std::declval<T2>().DoArchive(std::declval<Archive&>())),void>::type;
     template<typename>
     static constexpr std::false_type check(...);
-    typedef decltype(check<T>(0)) type;
+    using type = decltype(check<T>(nullptr));
   public:
     NGCORE_API static constexpr bool value = type::value;
   };
@@ -60,7 +60,7 @@ namespace ngcore
       typename std::is_same<decltype(std::declval<Archive>() & std::declval<T2&>()),Archive&>::type;
     template<typename>
     static constexpr std::false_type check(...);
-    typedef decltype(check<T>(nullptr)) type;
+    using type = decltype(check<T>(nullptr));
   public:
     NGCORE_API static constexpr bool value = type::value;
   };
@@ -107,7 +107,8 @@ namespace ngcore
     static void SetArchiveRegister(const std::string& classname, const ClassArchiveInfo& info);
     static bool IsRegistered(const std::string& classname);
   public:
-    Archive (bool ais_output) : is_output(ais_output), shared_ptr_count(0), ptr_count(0) { ; }
+    Archive (bool ais_output) : is_output(ais_output), shared_ptr_count(0), ptr_count(0)
+    shared_ptr2nr(), ptr2nr(), nr2shared_ptr(), nr2prt() { ; }
     virtual ~Archive() { ; }
 
     bool Output () { return is_output; }
diff --git a/libsrc/core/version.hpp b/libsrc/core/version.hpp
index f46e74af..5ffa8bb0 100644
--- a/libsrc/core/version.hpp
+++ b/libsrc/core/version.hpp
@@ -53,16 +53,16 @@ namespace ngcore
 
     std::string to_string() const
     { std::string vstring = "v" + std::to_string(mayor_);
-      if(minor_ || release || patch || git_hash.size())
+      if(minor_ || release || patch || !git_hash.empty())
         {
           vstring += "." + std::to_string(minor_);
-          if(release || patch || git_hash.size())
+          if(release || patch || !git_hash.empty())
             {
               vstring += "." + std::to_string(release);
-              if(patch || git_hash.size())
+              if(patch || !git_hash.empty())
                 {
                   vstring += "-" + std::to_string(patch);
-                  if(git_hash.size())
+                  if(!git_hash.empty())
                     vstring += "-" + git_hash;
                 }
             }