19 files changed, 536 insertions, 299 deletions

diff --git a/zen/file_access.cpp b/zen/file_access.cpp
index a81fdae0..88b70b14 100755
--- a/zen/file_access.cpp
+++ b/zen/file_access.cpp
@@ -381,7 +381,7 @@ void zen::renameFile(const Zstring& pathSource, const Zstring& pathTarget) //thr
         const Zstring parentPathSrc = beforeLast(pathSource, FILE_NAME_SEPARATOR, IF_MISSING_RETURN_NONE);
         const Zstring parentPathTrg = beforeLast(pathTarget, FILE_NAME_SEPARATOR, IF_MISSING_RETURN_NONE);
         //some (broken) devices may fail to rename case directly:
-        if (equalFilePath(parentPathSrc, parentPathTrg))
+        if (equalLocalPath(parentPathSrc, parentPathTrg))
         {
             if (fileNameSrc == fileNameTrg)
                 return; //non-sensical request
diff --git a/zen/file_error.h b/zen/file_error.h
index 086d0998..101d6543 100755
--- a/zen/file_error.h
+++ b/zen/file_error.h
@@ -45,7 +45,7 @@ DEFINE_NEW_FILE_ERROR(ErrorDifferentVolume);
 
 //----------- facilitate usage of std::wstring for error messages --------------------
 
-inline std::wstring fmtPath(const std::wstring& displayPath) { return L'\"' + displayPath + L'\"'; }
+inline std::wstring fmtPath(const std::wstring& displayPath) { return L'"' + displayPath + L'"'; }
 inline std::wstring fmtPath(const Zstring& displayPath) { return fmtPath(utfTo<std::wstring>(displayPath)); }
 inline std::wstring fmtPath(const wchar_t* displayPath) { return fmtPath(std::wstring(displayPath)); } //resolve overload ambiguity
 }
diff --git a/zen/file_traverser.cpp b/zen/file_traverser.cpp
index e342c8ec..cc6e0c0b 100755
--- a/zen/file_traverser.cpp
+++ b/zen/file_traverser.cpp
@@ -78,7 +78,7 @@ void zen::traverseFolder(const Zstring& dirPath,
                 if (onFolder)
                     onFolder({ itemName, itemPath });
             }
-            else //a file or named pipe, ect.
+            else //a file or named pipe, etc.
             {
                 if (onFile)
                     onFile({ itemName, itemPath, makeUnsigned(statData.st_size), statData.st_mtime });
diff --git a/zen/globals.h b/zen/globals.h
index 10975414..024147fa 100755
--- a/zen/globals.h
+++ b/zen/globals.h
@@ -14,14 +14,22 @@
 
 namespace zen
 {
-//solve static destruction order fiasco by providing shared ownership and serialized access to global variables
+/*
+Solve static destruction order fiasco by providing shared ownership and serialized access to global variables
+
+=>there may be accesses to "Global<T>::get()" during process shutdown e.g. _("") used by message in debug_minidump.cpp or by some detached thread assembling an error message!
+=> use trivially-destructible POD only!!!
+
+ATTENTION: function-static globals have the compiler generate "magic statics" == compiler-genenerated locking code which will crash or leak memory when accessed after global is "dead"
+           => "solved" by FunStatGlobal, but we can't have "too many" of these...
+*/
 template <class T>
-class Global
+class Global //don't use for function-scope statics!
 {
 public:
     Global()
     {
-        static_assert(std::is_trivially_destructible_v<Pod>, "this memory needs to live forever");
+        static_assert(std::is_trivially_constructible_v<Pod>&& std::is_trivially_destructible_v<Pod>, "this memory needs to live forever");
         assert(!pod_.inst && !pod_.spinLock); //we depend on static zero-initialization!
     }
 
@@ -52,16 +60,131 @@ public:
     }
 
 private:
-    //avoid static destruction order fiasco: there may be accesses to "Global<T>::get()" during process shutdown
-    //e.g. _("") used by message in debug_minidump.cpp or by some detached thread assembling an error message!
-    //=> use trivially-destructible POD only!!!
     struct Pod
     {
+        std::atomic<bool> spinLock; // { false }; rely entirely on static zero-initialization! => avoid potential contention with worker thread during Global<> construction!
+        //serialize access; can't use std::mutex: has non-trival destructor
         std::shared_ptr<T>* inst;   // = nullptr;
+    } pod_;
+};
+
+//===================================================================================================================
+//===================================================================================================================
+
+struct CleanUpEntry
+{
+    using CleanUpFunction = void (*)(void* callbackData);
+    CleanUpFunction cleanUpFun;
+    void*           callbackData;
+    CleanUpEntry*   prev;
+};
+void registerGlobalForDestruction(CleanUpEntry& entry);
+
+
+template <class T>
+class FunStatGlobal
+{
+public:
+    //No FunStatGlobal() or ~FunStatGlobal()!
+
+    std::shared_ptr<T> get()
+    {
+        static_assert(std::is_trivially_constructible_v<FunStatGlobal>&&
+                      std::is_trivially_destructible_v<FunStatGlobal>, "this class must not generate code for magic statics!");
+
+        while (pod_.spinLock.exchange(true)) ;
+        ZEN_ON_SCOPE_EXIT(pod_.spinLock = false);
+        if (pod_.inst)
+            return *pod_.inst;
+        return nullptr;
+    }
+
+    void set(std::unique_ptr<T>&& newInst)
+    {
+        std::shared_ptr<T>* tmpInst = nullptr;
+        if (newInst)
+            tmpInst = new std::shared_ptr<T>(std::move(newInst));
+        {
+            while (pod_.spinLock.exchange(true)) ;
+            ZEN_ON_SCOPE_EXIT(pod_.spinLock = false);
+
+            std::swap(pod_.inst, tmpInst);
+            registerDestruction();
+        }
+        delete tmpInst;
+    }
+
+    void initOnce(std::unique_ptr<T> (*getInitialValue)())
+    {
+        while (pod_.spinLock.exchange(true)) ;
+        ZEN_ON_SCOPE_EXIT(pod_.spinLock = false);
+
+        if (!pod_.cleanUpEntry.cleanUpFun)
+        {
+            assert(!pod_.inst);
+            if (std::unique_ptr<T> newInst = (*getInitialValue)())
+                pod_.inst = new std::shared_ptr<T>(std::move(newInst));
+            registerDestruction();
+        }
+    }
+
+private:
+    //call while holding pod_.spinLock
+    void registerDestruction()
+    {
+        assert(pod_.spinLock);
+
+        if (!pod_.cleanUpEntry.cleanUpFun)
+        {
+            pod_.cleanUpEntry.callbackData = this;
+            pod_.cleanUpEntry.cleanUpFun = [](void* callbackData)
+            {
+                auto thisPtr = static_cast<FunStatGlobal*>(callbackData);
+                thisPtr->set(nullptr);
+            };
+
+            registerGlobalForDestruction(pod_.cleanUpEntry);
+        }
+    }
+
+    struct Pod
+    {
         std::atomic<bool> spinLock; // { false }; rely entirely on static zero-initialization! => avoid potential contention with worker thread during Global<> construction!
         //serialize access; can't use std::mutex: has non-trival destructor
+        std::shared_ptr<T>* inst;   // = nullptr;
+        CleanUpEntry cleanUpEntry;
     } pod_;
 };
+
+
+inline
+void registerGlobalForDestruction(CleanUpEntry& entry)
+{
+    static struct
+    {
+        std::atomic<bool> spinLock;
+        CleanUpEntry*     head;
+    } cleanUpList;
+
+    static_assert(std::is_trivially_constructible_v<decltype(cleanUpList)>&&
+                  std::is_trivially_destructible_v<decltype(cleanUpList)>, "we must not generate code for magic statics!");
+
+    while (cleanUpList.spinLock.exchange(true)) ;
+    ZEN_ON_SCOPE_EXIT(cleanUpList.spinLock = false);
+
+    std::atexit([]
+    {
+        while (cleanUpList.spinLock.exchange(true)) ;
+        ZEN_ON_SCOPE_EXIT(cleanUpList.spinLock = false);
+
+        (*cleanUpList.head->cleanUpFun)(cleanUpList.head->callbackData);
+        cleanUpList.head = cleanUpList.head->prev; //nicely clean up in reverse order of construction
+    });
+
+    entry.prev = cleanUpList.head;
+    cleanUpList.head = &entry;
+
+}
 }
 
 #endif //GLOBALS_H_8013740213748021573485
diff --git a/zen/guid.h b/zen/guid.h
index 89e800b5..a26688f8 100755
--- a/zen/guid.h
+++ b/zen/guid.h
@@ -9,6 +9,7 @@
 
     #include <fcntl.h> //open
     #include <unistd.h> //close
+    #include <zen/sys_error.h>
     //#include <uuid/uuid.h> -> uuid_generate(), uuid_unparse(); avoid additional dependency for "sudo apt-get install uuid-dev"
 
 
diff --git a/zen/http.cpp b/zen/http.cpp
index d06d3309..1f89bf20 100755
--- a/zen/http.cpp
+++ b/zen/http.cpp
@@ -26,9 +26,9 @@ public:
 
         const bool useTls = [&]
         {
-            if (startsWith(url, Zstr("http://"), CmpAsciiNoCase()))
+            if (startsWithAsciiNoCase(url, Zstr("http://")))
                 return false;
-            if (startsWith(url, Zstr("https://"), CmpAsciiNoCase()))
+            if (startsWithAsciiNoCase(url, Zstr("https://")))
                 return true;
             throw SysError(L"URL uses unexpected protocol.");
         }();
@@ -57,35 +57,16 @@ public:
 
         //https://www.w3.org/Protocols/HTTP/1.0/spec.html#Request-Line
         std::string msg = (postParams ? "POST " : "GET ") + utfTo<std::string>(page) + " HTTP/1.0\r\n";
-        for (const auto& item : headers)
-            msg += item.first + ": " + item.second + "\r\n";
+        for (const auto& [name, value] : headers)
+            msg += name + ": " + value + "\r\n";
         msg += "\r\n";
         msg += postBuf;
 
         //send request
         for (size_t bytesToSend = msg.size(); bytesToSend > 0;)
-        {
-            int bytesSent = 0;
-            for (;;)
-            {
-                bytesSent = ::send(socket_->get(),                //_In_       SOCKET s,
-                                   &*(msg.end() - bytesToSend),   //_In_ const char   *buf,
-                                   static_cast<int>(bytesToSend), //_In_       int    len,
-                                   0);                            //_In_       int    flags
-                if (bytesSent >= 0 || errno != EINTR)
-                    break;
-            }
-            if (bytesSent < 0)
-                THROW_LAST_SYS_ERROR_WSA(L"send");
-            if (bytesSent > static_cast<int>(bytesToSend))
-                throw SysError(L"send: buffer overflow.");
-            if (bytesSent == 0)
-                throw SysError(L"send: zero bytes processed");
-
-            bytesToSend -= bytesSent;
-        }
-        if (::shutdown(socket_->get(), SHUT_WR) != 0)
-            THROW_LAST_SYS_ERROR_WSA(L"shutdown");
+            bytesToSend -= tryWriteSocket(socket_->get(), &*(msg.end() - bytesToSend), bytesToSend); //throw SysError
+
+        shutdownSocketSend(socket_->get()); //throw SysError
 
         //receive response:
         std::string headBuf;
@@ -116,7 +97,7 @@ public:
 
         const std::vector<std::string> statusItems = split(statusBuf, ' ', SplitType::ALLOW_EMPTY); //HTTP-Version SP Status-Code SP Reason-Phrase CRLF
         if (statusItems.size() < 2 || !startsWith(statusItems[0], "HTTP/"))
-            throw SysError(L"Invalid HTTP response: \"" + utfTo<std::wstring>(statusBuf) + L"\"");
+            throw SysError(L"Invalid HTTP response: \"" + utfTo<std::wstring>(statusBuf) + L'"');
 
         statusCode_ = stringTo<int>(statusItems[1]);
 
@@ -175,8 +156,6 @@ public:
 private:
     size_t tryRead(void* buffer, size_t bytesToRead) //throw SysError; may return short, only 0 means EOF!
     {
-        if (bytesToRead == 0) //"read() with a count of 0 returns zero" => indistinguishable from end of file! => check!
-            throw std::logic_error("Contract violation! " + std::string(__FILE__) + ":" + numberTo<std::string>(__LINE__));
         assert(bytesToRead <= getBlockSize()); //block size might be 1000 while reading HTTP header
 
         if (contentRemaining_ >= 0)
@@ -185,21 +164,7 @@ private:
                 return 0;
             bytesToRead = static_cast<size_t>(std::min(static_cast<int64_t>(bytesToRead), contentRemaining_)); //[!] contentRemaining_ > 4 GB possible!
         }
-        int bytesReceived = 0;
-        for (;;)
-        {
-            bytesReceived = ::recv(socket_->get(),                //_In_  SOCKET s,
-                                   static_cast<char*>(buffer),    //_Out_ char   *buf,
-                                   static_cast<int>(bytesToRead), //_In_  int    len,
-                                   0);                            //_In_  int    flags
-            if (bytesReceived >= 0 || errno != EINTR)
-                break;
-        }
-        if (bytesReceived < 0)
-            THROW_LAST_SYS_ERROR_WSA(L"recv");
-        if (static_cast<size_t>(bytesReceived) > bytesToRead) //better safe than sorry
-            throw SysError(L"HttpInputStream::tryRead: buffer overflow.");
-
+        const size_t bytesReceived = tryReadSocket(socket_->get(), buffer, bytesToRead); //throw SysError; may return short, only 0 means EOF!
         if (contentRemaining_ >= 0)
             contentRemaining_ -= bytesReceived;
 
@@ -325,8 +290,8 @@ std::string urldecode(const std::string& str)
 std::string zen::xWwwFormUrlEncode(const std::vector<std::pair<std::string, std::string>>& paramPairs)
 {
     std::string output;
-    for (const auto& pair : paramPairs)
-        output += urlencode(pair.first) + '=' + urlencode(pair.second) + '&';
+    for (const auto& [name, value] : paramPairs)
+        output += urlencode(name) + '=' + urlencode(value) + '&';
     //encode both key and value: https://www.w3.org/TR/html401/interact/forms.html#h-17.13.4.1
     if (!output.empty())
         output.pop_back();
diff --git a/zen/i18n.h b/zen/i18n.h
index 45762861..2ecee45a 100755
--- a/zen/i18n.h
+++ b/zen/i18n.h
@@ -59,10 +59,10 @@ std::shared_ptr<const TranslationHandler> getTranslator();
 namespace impl
 {
 inline
-Global<const TranslationHandler>& refGlobalTranslationHandler()
+FunStatGlobal<const TranslationHandler>& refGlobalTranslationHandler()
 {
     //getTranslator() may be called even after static objects of this translation unit are destroyed!
-    static Global<const TranslationHandler> inst; //external linkage even in header!
+    static FunStatGlobal<const TranslationHandler> inst; //external linkage even in header!
     return inst;
 }
 }
diff --git a/zen/legacy_compiler.h b/zen/legacy_compiler.h
index e9d50b97..16d87c53 100755
--- a/zen/legacy_compiler.h
+++ b/zen/legacy_compiler.h
@@ -7,14 +7,11 @@
 #ifndef LEGACY_COMPILER_H_839567308565656789
 #define LEGACY_COMPILER_H_839567308565656789
 
-    #include <optional>
-
 namespace std
 {
 //https://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html
 //https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations
 
-
 }
 
 #endif //LEGACY_COMPILER_H_839567308565656789
diff --git a/zen/scope_guard.h b/zen/scope_guard.h
index d056bb2a..9eff6c1f 100755
--- a/zen/scope_guard.h
+++ b/zen/scope_guard.h
@@ -10,6 +10,7 @@
 #include <cassert>
 #include <exception>
 #include "type_traits.h"
+#include "legacy_compiler.h" //std::uncaught_exceptions
 
 //best of Zen, Loki and C++17
 
@@ -103,8 +104,8 @@ auto makeGuard(F&& fun) { return ScopeGuard<runMode, std::decay_t<F>>(std::forwa
 #define ZEN_CHECK_CASE_FOR_CONSTANT_IMPL(X) L ## X
 
 
-#define ZEN_ON_SCOPE_EXIT(X)    auto ZEN_CONCAT(dummy, __LINE__) = zen::makeGuard<zen::ScopeGuardRunMode::ON_EXIT   >([&]{ X; }); (void)ZEN_CONCAT(dummy, __LINE__);
-#define ZEN_ON_SCOPE_FAIL(X)    auto ZEN_CONCAT(dummy, __LINE__) = zen::makeGuard<zen::ScopeGuardRunMode::ON_FAIL   >([&]{ X; }); (void)ZEN_CONCAT(dummy, __LINE__);
-#define ZEN_ON_SCOPE_SUCCESS(X) auto ZEN_CONCAT(dummy, __LINE__) = zen::makeGuard<zen::ScopeGuardRunMode::ON_SUCCESS>([&]{ X; }); (void)ZEN_CONCAT(dummy, __LINE__);
+#define ZEN_ON_SCOPE_EXIT(X)    auto ZEN_CONCAT(scopeGuard, __LINE__) = zen::makeGuard<zen::ScopeGuardRunMode::ON_EXIT   >([&]{ X; }); (void)ZEN_CONCAT(scopeGuard, __LINE__);
+#define ZEN_ON_SCOPE_FAIL(X)    auto ZEN_CONCAT(scopeGuard, __LINE__) = zen::makeGuard<zen::ScopeGuardRunMode::ON_FAIL   >([&]{ X; }); (void)ZEN_CONCAT(scopeGuard, __LINE__);
+#define ZEN_ON_SCOPE_SUCCESS(X) auto ZEN_CONCAT(scopeGuard, __LINE__) = zen::makeGuard<zen::ScopeGuardRunMode::ON_SUCCESS>([&]{ X; }); (void)ZEN_CONCAT(scopeGuard, __LINE__);
 
 #endif //SCOPE_GUARD_H_8971632487321434
diff --git a/zen/shell_execute.h b/zen/shell_execute.h
index 0802fbcb..98824d70 100755
--- a/zen/shell_execute.h
+++ b/zen/shell_execute.h
@@ -39,7 +39,7 @@ void shellExecute(const Zstring& command, ExecutionType type) //throw FileError
     if (type == ExecutionType::SYNC)
     {
         //Posix ::system() - execute a shell command
-        const int rv = ::system(command.c_str()); //do NOT use std::system as its documentation says nothing about "WEXITSTATUS(rv)", ect...
+        const int rv = ::system(command.c_str()); //do NOT use std::system as its documentation says nothing about "WEXITSTATUS(rv)", etc...
         if (rv == -1 || WEXITSTATUS(rv) == 127)
             throw FileError(_("Incorrect command line:") + L"\n" + utfTo<std::wstring>(command));
         //http://linux.die.net/man/3/system    "In case /bin/sh could not be executed, the exit status will be that of a command that does exit(127)"
@@ -73,7 +73,7 @@ void shellExecute(const Zstring& command, ExecutionType type) //throw FileError
 inline
 void openWithDefaultApplication(const Zstring& itemPath) //throw FileError
 {
-    shellExecute("xdg-open \"" + itemPath + "\"", ExecutionType::ASYNC); //
+    shellExecute("xdg-open \"" + itemPath +  '"', ExecutionType::ASYNC); //
 }
 }
 
diff --git a/zen/socket.h b/zen/socket.h
index e551a5ba..33ac2e50 100755
--- a/zen/socket.h
+++ b/zen/socket.h
@@ -20,6 +20,12 @@ namespace zen
     do { const ErrorCode ecInternal = getLastError(); throw SysError(formatSystemError(functionName, ecInternal)); } while (false)
 
 
+//patch up socket portability:
+using SocketType = int;
+const SocketType invalidSocket = -1;
+inline void closeSocket(SocketType s) { ::close(s); }
+
+
 //Winsock needs to be initialized before calling any of these functions! (WSAStartup/WSACleanup)
 
 class Socket //throw SysError
@@ -67,18 +73,78 @@ public:
 
     ~Socket() { closeSocket(socket_); }
 
-    using SocketType = int;
     SocketType get() const { return socket_; }
 
 private:
     Socket           (const Socket&) = delete;
     Socket& operator=(const Socket&) = delete;
 
-    static const SocketType invalidSocket = -1;
-    static void closeSocket(SocketType s) { ::close(s); }
-
     SocketType socket_ = invalidSocket;
 };
+
+
+//more socket helper functions:
+namespace
+{
+size_t tryReadSocket(SocketType socket, void* buffer, size_t bytesToRead) //throw SysError; may return short, only 0 means EOF!
+{
+    if (bytesToRead == 0) //"read() with a count of 0 returns zero" => indistinguishable from end of file! => check!
+        throw std::logic_error("Contract violation! " + std::string(__FILE__) + ":" + numberTo<std::string>(__LINE__));
+
+    int bytesReceived = 0;
+    for (;;)
+    {
+        bytesReceived = ::recv(socket,                        //_In_  SOCKET s,
+                               static_cast<char*>(buffer),    //_Out_ char   *buf,
+                               static_cast<int>(bytesToRead), //_In_  int    len,
+                               0);                            //_In_  int    flags
+        if (bytesReceived >= 0 || errno != EINTR)
+            break;
+    }
+    if (bytesReceived < 0)
+        THROW_LAST_SYS_ERROR_WSA(L"recv");
+
+    if (static_cast<size_t>(bytesReceived) > bytesToRead) //better safe than sorry
+        throw SysError(L"HttpInputStream::tryRead: buffer overflow.");
+
+    return bytesReceived; //"zero indicates end of file"
+}
+
+
+size_t tryWriteSocket(SocketType socket, const void* buffer, size_t bytesToWrite) //throw SysError; may return short! CONTRACT: bytesToWrite > 0
+{
+    if (bytesToWrite == 0)
+        throw std::logic_error("Contract violation! " + std::string(__FILE__) + ":" + numberTo<std::string>(__LINE__));
+
+    int bytesWritten = 0;
+    for (;;)
+    {
+        bytesWritten = ::send(socket,                        //_In_       SOCKET s,
+                              static_cast<const char*>(buffer), //_In_ const char   *buf,
+                              static_cast<int>(bytesToWrite),   //_In_       int    len,
+                              0);                               //_In_       int    flags
+        if (bytesWritten >= 0 || errno != EINTR)
+            break;
+    }
+    if (bytesWritten < 0)
+        THROW_LAST_SYS_ERROR_WSA(L"send");
+    if (bytesWritten > static_cast<int>(bytesToWrite))
+        throw SysError(L"send: buffer overflow.");
+    if (bytesWritten == 0)
+        throw SysError(L"send: zero bytes processed");
+
+    return bytesWritten;
+}
+}
+
+
+inline
+void shutdownSocketSend(SocketType socket) //throw SysError
+{
+    if (::shutdown(socket, SHUT_WR) != 0)
+        THROW_LAST_SYS_ERROR_WSA(L"shutdown");
+}
+
 }
 
 #endif //SOCKET_H_23498325972583947678456437
diff --git a/zen/stl_tools.h b/zen/stl_tools.h
index be9bf710..c3a9bf8f 100755
--- a/zen/stl_tools.h
+++ b/zen/stl_tools.h
@@ -12,6 +12,7 @@
 #include <vector>
 #include <memory>
 #include <algorithm>
+#include <optional>
 #include "string_traits.h"
 #include "build_info.h"
 
diff --git a/zen/string_tools.h b/zen/string_tools.h
index 8746722a..657c70d5 100755
--- a/zen/string_tools.h
+++ b/zen/string_tools.h
@@ -26,32 +26,30 @@ template <class Char> bool isWhiteSpace(Char c);
 template <class Char> bool isDigit     (Char c); //not exactly the same as "std::isdigit" -> we consider '0'-'9' only!
 template <class Char> bool isHexDigit  (Char c);
 template <class Char> bool isAsciiAlpha(Char c);
+template <class Char> bool isAsciiString(const Char* str);
 template <class Char> Char asciiToLower(Char c);
 template <class Char> Char asciiToUpper(Char c);
 
-//case-sensitive comparison (compile-time correctness:  use different number of arguments as STL comparison predicates!)
-struct CmpBinary { template <class Char> int operator()(const Char* lhs, size_t lhsLen, const Char* rhs, size_t rhsLen) const; };
+//both S and T can be strings or char/wchar_t arrays or single char/wchar_t
+template <class S, class T> bool contains(const S& str, const T& term);
 
-//basic case-insensitive comparison (considering A-Z only!)
-struct CmpAsciiNoCase { template <class Char> int operator()(const Char* lhs, size_t lhsLen, const Char* rhs, size_t rhsLen) const; };
+template <class S, class T> bool startsWith           (const S& str, const T& prefix);
+template <class S, class T> bool startsWithAsciiNoCase(const S& str, const T& prefix);
 
-struct LessAsciiNoCase
-{
-    template <class S> //don't support heterogenous input! => use as container predicate only!
-    bool operator()(const S& lhs, const S& rhs) const { return CmpAsciiNoCase()(strBegin(lhs), strLength(lhs), strBegin(rhs), strLength(rhs)) < 0; }
-};
+template <class S, class T> bool endsWith           (const S& str, const T& postfix);
+template <class S, class T> bool endsWithAsciiNoCase(const S& str, const T& postfix);
 
-//both S and T can be strings or char/wchar_t arrays or simple char/wchar_t
-template <class S, class T> bool contains(const S& str, const T& term);
+template <class S, class T> bool equalString     (const S& lhs, const T& rhs);
+template <class S, class T> bool equalAsciiNoCase(const S& lhs, const T& rhs);
 
-template <class S, class T>                 bool startsWith(const S& str, const T& prefix);
-template <class S, class T, class Function> bool startsWith(const S& str, const T& prefix,  Function cmpStringFun);
+template <class S, class T> int compareString     (const S& lhs, const T& rhs);
+template <class S, class T> int compareAsciiNoCase(const S& lhs, const T& rhs); //basic case-insensitive comparison (considering A-Z only!)
 
-template <class S, class T>                 bool endsWith  (const S& str, const T& postfix);
-template <class S, class T, class Function> bool endsWith  (const S& str, const T& postfix, Function cmpStringFun);
+struct LessAsciiNoCase //STL container predicate
+{
+    template <class S> bool operator()(const S& lhs, const S& rhs) const { return compareAsciiNoCase(lhs, rhs) < 0; }
+};
 
-template <class S, class T>                 bool strEqual(const S& lhs, const T& rhs);
-template <class S, class T, class Function> bool strEqual(const S& lhs, const T& rhs, Function cmpStringFun);
 
 enum FailureReturnVal
 {
@@ -152,6 +150,17 @@ bool isAsciiAlpha(Char c)
 
 
 template <class Char> inline
+bool isAsciiString(const Char* str)
+{
+    static_assert(std::is_same_v<Char, char> || std::is_same_v<Char, wchar_t>);
+    for (Char c = *str; c != 0; c = *++str)
+        if (zen::makeUnsigned(c) >= 128)
+            return false;
+    return true;
+}
+
+
+template <class Char> inline
 Char asciiToLower(Char c)
 {
     if (static_cast<Char>('A') <= c && c <= static_cast<Char>('Z'))
@@ -169,41 +178,103 @@ Char asciiToUpper(Char c)
 }
 
 
-template <class S, class T, class Function> inline
-bool startsWith(const S& str, const T& prefix, Function cmpStringFun)
+namespace impl
+{
+inline int strcmpWithNulls(const char*    ptr1, const char*    ptr2, size_t num) { return std:: memcmp(ptr1, ptr2, num); } //support embedded 0, unlike strncmp/wcsncmp!
+inline int strcmpWithNulls(const wchar_t* ptr1, const wchar_t* ptr2, size_t num) { return std::wmemcmp(ptr1, ptr2, num); } //
+
+
+template <class Char> inline
+int strcmpAsciiNoCase(const Char* lhs, const Char* rhs, size_t len)
+{
+    while (len-- > 0)
+    {
+        const Char charL = asciiToLower(*lhs++); //ordering: lower-case chars have higher code points than uppper-case
+        const Char charR = asciiToLower(*rhs++); //
+        if (charL != charR)
+            return static_cast<unsigned int>(charL) - static_cast<unsigned int>(charR); //unsigned char-comparison is the convention!
+        //unsigned underflow is well-defined!
+    }
+    return 0;
+}
+}
+
+
+template <class S, class T> inline
+bool startsWith(const S& str, const T& prefix)
 {
     const size_t pfLen = strLength(prefix);
-    if (strLength(str) < pfLen)
-        return false;
+    return strLength(str) >= pfLen && impl::strcmpWithNulls(strBegin(str), strBegin(prefix), pfLen) == 0;
+}
+
 
-    return cmpStringFun(strBegin(str),    pfLen,
-                        strBegin(prefix), pfLen) == 0;
+template <class S, class T> inline
+bool startsWithAsciiNoCase(const S& str, const T& prefix)
+{
+    const size_t pfLen = strLength(prefix);
+    return strLength(str) >= pfLen && impl::strcmpAsciiNoCase(strBegin(str), strBegin(prefix), pfLen) == 0;
 }
 
 
-template <class S, class T, class Function> inline
-bool endsWith(const S& str, const T& postfix, Function cmpStringFun)
+template <class S, class T> inline
+bool endsWith(const S& str, const T& postfix)
 {
     const size_t strLen = strLength(str);
     const size_t pfLen  = strLength(postfix);
-    if (strLen < pfLen)
-        return false;
+    return strLen >= pfLen && impl::strcmpWithNulls(strBegin(str) + strLen - pfLen, strBegin(postfix), pfLen) == 0;
+}
+
+
+template <class S, class T> inline
+bool endsWithAsciiNoCase(const S& str, const T& postfix)
+{
+    const size_t strLen = strLength(str);
+    const size_t pfLen  = strLength(postfix);
+    return strLen >= pfLen && impl::strcmpAsciiNoCase(strBegin(str) + strLen - pfLen, strBegin(postfix), pfLen) == 0;
+}
+
 
-    return cmpStringFun(strBegin(str) + strLen - pfLen, pfLen,
-                        strBegin(postfix), pfLen) == 0;
+template <class S, class T> inline
+bool equalString(const S& lhs, const T& rhs)
+{
+    const size_t lhsLen = strLength(lhs);
+    return lhsLen == strLength(rhs) && impl::strcmpWithNulls(strBegin(lhs), strBegin(rhs), lhsLen) == 0;
 }
 
 
-template <class S, class T, class Function> inline
-bool strEqual(const S& lhs, const T& rhs, Function cmpStringFun)
+template <class S, class T> inline
+bool equalAsciiNoCase(const S& lhs, const T& rhs)
+{
+    const size_t lhsLen = strLength(lhs);
+    return lhsLen == strLength(rhs) && impl::strcmpAsciiNoCase(strBegin(lhs), strBegin(rhs), lhsLen) == 0;
+}
+
+
+template <class S, class T> inline
+int compareString(const S& lhs, const T& rhs)
 {
-    return cmpStringFun(strBegin(lhs), strLength(lhs), strBegin(rhs), strLength(rhs)) == 0;
+    const size_t lhsLen = strLength(lhs);
+    const size_t rhsLen = strLength(rhs);
+
+    //length check *after* strcmpWithNulls(): we do care about natural ordering: e.g. for "compareString(makeUpperCopy(lhs), makeUpperCopy(rhs))"
+    const int rv = impl::strcmpWithNulls(strBegin(lhs), strBegin(rhs), std::min(lhsLen, rhsLen));
+    if (rv != 0)
+        return rv;
+    return static_cast<int>(lhsLen) - static_cast<int>(rhsLen);
 }
 
 
-template <class S, class T> inline bool startsWith(const S& str, const T& prefix ) { return startsWith(str, prefix,  CmpBinary()); }
-template <class S, class T> inline bool endsWith  (const S& str, const T& postfix) { return endsWith  (str, postfix, CmpBinary()); }
-template <class S, class T> inline bool strEqual  (const S& lhs, const T& rhs    ) { return strEqual  (lhs, rhs,     CmpBinary()); }
+template <class S, class T> inline
+int compareAsciiNoCase(const S& lhs, const T& rhs)
+{
+    const size_t lhsLen = strLength(lhs);
+    const size_t rhsLen = strLength(rhs);
+
+    const int rv = impl::strcmpAsciiNoCase(strBegin(lhs), strBegin(rhs), std::min(lhsLen, rhsLen));
+    if (rv != 0)
+        return rv;
+    return static_cast<int>(lhsLen) - static_cast<int>(rhsLen);
+}
 
 
 template <class S, class T> inline
@@ -464,42 +535,12 @@ struct CopyStringToString<T, T> //perf: we don't need a deep copy if string type
     template <class S>
     T copy(S&& str) const { return std::forward<S>(str); }
 };
-
-inline int strcmpWithNulls(const char*    ptr1, const char*    ptr2, size_t num) { return std::memcmp (ptr1, ptr2, num); }
-inline int strcmpWithNulls(const wchar_t* ptr1, const wchar_t* ptr2, size_t num) { return std::wmemcmp(ptr1, ptr2, num); }
 }
 
 template <class T, class S> inline
 T copyStringTo(S&& str) { return impl::CopyStringToString<std::decay_t<S>, T>().copy(std::forward<S>(str)); }
 
 
-template <class Char> inline
-int CmpBinary::operator()(const Char* lhs, size_t lhsLen, const Char* rhs, size_t rhsLen) const
-{
-    //support embedded 0, unlike strncmp/wcsncmp!
-    const int rv = impl::strcmpWithNulls(lhs, rhs, std::min(lhsLen, rhsLen));
-    if (rv != 0)
-        return rv;
-    return static_cast<int>(lhsLen) - static_cast<int>(rhsLen);
-}
-
-
-template <class Char> inline
-int CmpAsciiNoCase::operator()(const Char* lhs, size_t lhsLen, const Char* rhs, size_t rhsLen) const
-{
-    const auto* const lhsLast = lhs + std::min(lhsLen, rhsLen);
-    while (lhs != lhsLast)
-    {
-        const Char charL = asciiToLower(*lhs++); //ordering: lower-case chars have higher code points than uppper-case
-        const Char charR = asciiToLower(*rhs++); //
-        if (charL != charR)
-            return static_cast<unsigned int>(charL) - static_cast<unsigned int>(charR); //unsigned char-comparison is the convention!
-        //unsigned underflow is well-defined!
-    }
-    return static_cast<int>(lhsLen) - static_cast<int>(rhsLen);
-}
-
-
 namespace impl
 {
 template <class Num> inline
diff --git a/zen/thread.cpp b/zen/thread.cpp
index 8016d4a9..08bfaa25 100755
--- a/zen/thread.cpp
+++ b/zen/thread.cpp
@@ -34,10 +34,7 @@ uint64_t getThreadIdNative()
 }
 
 
-struct InitMainThreadIdOnStartup
-{
-    InitMainThreadIdOnStartup() { getMainThreadId(); }
-} startupInitMainThreadId;
+const uint64_t globalMainThreadId = getThreadId(); //avoid code-gen for "magic static"!
 }
 
 
@@ -50,6 +47,9 @@ uint64_t zen::getThreadId()
 
 uint64_t zen::getMainThreadId()
 {
-    static const uint64_t mainThreadId = getThreadId();
-    return mainThreadId;
+    //don't make this a function-scope static (avoid code-gen for "magic static")
+    if (globalMainThreadId == 0) //might be called during static initialization
+        return getThreadId();
+
+    return globalMainThreadId;
 }
diff --git a/zen/time.h b/zen/time.h
index b06d3d15..a32e28e3 100755
--- a/zen/time.h
+++ b/zen/time.h
@@ -327,13 +327,13 @@ TimeComp parseTime(const String& format, const String2& str, UserDefinedFormatTa
     const CharType*       itStr = strBegin(str);
     const CharType* const strLast = itStr + strLength(str);
 
-    auto extractNumber = [&](int& result, size_t digitCount) -> bool
+    auto extractNumber = [&](int& result, size_t digitCount)
     {
         if (strLast - itStr < makeSigned(digitCount))
             return false;
 
-        if (std::any_of(itStr, itStr + digitCount, [](CharType c) { return !isDigit(c); }))
-        return false;
+        if (!std::all_of(itStr, itStr + digitCount, isDigit<CharType>))
+            return false;
 
         result = zen::stringTo<int>(StringRef<const CharType>(itStr, itStr + digitCount));
         itStr += digitCount;
diff --git a/zen/type_traits.h b/zen/type_traits.h
index 2d4e7a97..8783cb6a 100755
--- a/zen/type_traits.h
+++ b/zen/type_traits.h
@@ -8,7 +8,6 @@
 #define TYPE_TRAITS_H_3425628658765467
 
 #include <type_traits>
-#include "legacy_compiler.h"
 
 //http://en.cppreference.com/w/cpp/header/type_traits
 
diff --git a/zen/utf.h b/zen/utf.h
index da6aaf97..5a095874 100755
--- a/zen/utf.h
+++ b/zen/utf.h
@@ -192,7 +192,7 @@ public:
     std::optional<CodePoint> getNext()
     {
         if (it_ == last_)
-            return std::nullopt; //GCC 8.2 bug: -Wmaybe-uninitialized for "return {};"
+            return std::nullopt;
 
         const Char8 ch = *it_++;
         CodePoint cp = ch;
@@ -313,7 +313,7 @@ bool isValidUtf(const UtfString& str)
     using namespace impl;
 
     UtfDecoder<GetCharTypeT<UtfString>> decoder(strBegin(str), strLength(str));
-    while (std::optional<CodePoint> cp = decoder.getNext())
+    while (const std::optional<CodePoint> cp = decoder.getNext())
         if (*cp == REPLACEMENT_CHAR)
             return false;
 
@@ -367,7 +367,7 @@ TargetString utfTo(const SourceString& str, std::false_type)
     TargetString output;
 
     UtfDecoder<CharSrc> decoder(strBegin(str), strLength(str));
-    while (std::optional<CodePoint> cp = decoder.getNext())
+    while (const std::optional<CodePoint> cp = decoder.getNext())
         codePointToUtf<CharTrg>(*cp, [&](CharTrg c) { output += c; });
 
     return output;
diff --git a/zen/zstring.cpp b/zen/zstring.cpp
index 8bf77a0b..68609030 100755
--- a/zen/zstring.cpp
+++ b/zen/zstring.cpp
@@ -8,9 +8,102 @@
 #include <stdexcept>
 #include "utf.h"
 
+    #include <gtk/gtk.h>
+    #include "sys_error.h"
 
 using namespace zen;
 
+
+Zstring makeUpperCopy(const Zstring& str)
+{
+    //fast pre-check:
+    if (isAsciiString(str.c_str())) //perf: in the range of 3.5ns
+    {
+        Zstring output = str;
+        for (Zchar& c : output) c = asciiToUpper(c);
+        return output;
+    }
+
+    Zstring strNorm = getUnicodeNormalForm(str);
+    try
+    {
+        static_assert(sizeof(impl::CodePoint) == sizeof(gunichar));
+        Zstring output;
+        output.reserve(strNorm.size());
+
+        impl::UtfDecoder<char> decoder(strNorm.c_str(), strNorm.size());
+        while (const std::optional<impl::CodePoint> cp = decoder.getNext())
+            impl::codePointToUtf<char>(::g_unichar_toupper(*cp), [&](char c) { output += c; }); //don't use std::towupper: *incomplete* and locale-dependent!
+
+        return output;
+
+    }
+    catch (const SysError& e)
+    {
+        (void)e;
+        assert(false);
+        return str;
+    }
+}
+
+
+Zstring getUnicodeNormalForm(const Zstring& str)
+{
+    //fast pre-check:
+    if (isAsciiString(str.c_str())) //perf: in the range of 3.5ns
+        return str; //god bless our ref-counting! => save output string memory consumption!
+
+    //Example: const char* decomposed  = "\x6f\xcc\x81";
+    //         const char* precomposed = "\xc3\xb3";
+    try
+    {
+        gchar* outStr = ::g_utf8_normalize (str.c_str(), str.length(), G_NORMALIZE_DEFAULT_COMPOSE);
+        if (!outStr)
+            throw SysError(L"g_utf8_normalize: conversion failed. (" + utfTo<std::wstring>(str) + L")");
+        ZEN_ON_SCOPE_EXIT(::g_free(outStr));
+        return outStr;
+
+    }
+    catch (const SysError& e)
+    {
+        (void)e;
+        assert(false);
+        return str;
+    }
+}
+
+
+Zstring replaceCpyAsciiNoCase(const Zstring& str, const Zstring& oldTerm, const Zstring& newTerm)
+{
+    if (oldTerm.empty())
+        return str;
+    
+    Zstring strU = str;    
+    Zstring oldU = oldTerm;
+          
+    for (Zchar& c : strU) c = asciiToUpper(c); //can't use makeUpperCopy(): input/output sizes may differ!
+    for (Zchar& c : oldU) c = asciiToUpper(c); //
+
+    Zstring output;
+
+    for (size_t pos = 0;;)
+    {
+        const size_t posFound = strU.find(oldU, pos);
+        if (posFound == Zstring::npos)
+        {
+            if (pos == 0) //optimize "oldTerm not found": return ref-counted copy
+                return str; 
+            output.append(str.begin() + pos, str.end());
+            return output;
+        }
+
+        output.append(str.begin() + pos, str.begin() + posFound);
+        output += newTerm;
+        pos = posFound + oldTerm.size();
+    }
+}
+
+
 /*
 MSDN "Handling Sorting in Your Applications": https://msdn.microsoft.com/en-us/library/windows/desktop/dd318144
 
@@ -33,8 +126,14 @@ OS X (UTF8 char)
 ________________________
 time per call | function
 */
+int compareLocalPath(const Zstring& lhs, const Zstring& rhs)
+{
+    assert(lhs.find(Zchar('\0')) == Zstring::npos); //don't expect embedded nulls!
+    assert(rhs.find(Zchar('\0')) == Zstring::npos); //
 
+    return compareString(lhs, rhs);
 
+}
 
 
 namespace
@@ -43,7 +142,7 @@ int compareNoCaseUtf8(const char* lhs, size_t lhsLen, const char* rhs, size_t rh
 {
     //- strncasecmp implements ASCII CI-comparsion only! => signature is broken for UTF8-input; toupper() similarly doesn't support Unicode
     //- wcsncasecmp: https://opensource.apple.com/source/Libc/Libc-763.12/string/wcsncasecmp-fbsd.c
-    // => re-implement comparison based on towlower() to avoid memory allocations
+    // => re-implement comparison based on g_unichar_tolower() to avoid memory allocations
 
     impl::UtfDecoder<char> decL(lhs, lhsLen);
     impl::UtfDecoder<char> decR(rhs, rhsLen);
@@ -54,23 +153,35 @@ int compareNoCaseUtf8(const char* lhs, size_t lhsLen, const char* rhs, size_t rh
         if (!cpL || !cpR)
             return static_cast<int>(!cpR) - static_cast<int>(!cpL);
 
-        //support unit-testing on Windows: CodePoint is truncated to wchar_t
-        static_assert(sizeof(wchar_t) == sizeof(impl::CodePoint));
+        static_assert(sizeof(gunichar) == sizeof(impl::CodePoint));
 
-        const wchar_t charL = ::towlower(static_cast<wchar_t>(*cpL)); //ordering: towlower() converts to higher code points than towupper()
-        const wchar_t charR = ::towlower(static_cast<wchar_t>(*cpR)); //uses LC_CTYPE category of current locale
+        const gunichar charL = ::g_unichar_toupper(*cpL); //note: tolower can be ambiguous, so don't use:
+        const gunichar charR = ::g_unichar_toupper(*cpR); //e.g. "Σ" (upper case) can be lower-case "ς" in the end of the word or "σ" in the middle.
         if (charL != charR)
+            //ordering: "to lower" converts to higher code points than "to upper"
             return static_cast<unsigned int>(charL) - static_cast<unsigned int>(charR); //unsigned char-comparison is the convention!
         //unsigned underflow is well-defined!
     }
 }
+
 }
 
 
-int cmpStringNaturalLinuxTest(const char* lhs, size_t lhsLen, const char* rhs, size_t rhsLen)
+int compareNatural(const Zstring& lhs, const Zstring& rhs)
 {
-    const char* const lhsEnd = lhs + lhsLen;
-    const char* const rhsEnd = rhs + rhsLen;
+    //Unicode normal forms:
+    //      Windows: CompareString() already ignores NFD/NFC differences: nice...
+    //      Linux:  g_unichar_toupper() can't ignore differences
+    //      macOS:  CFStringCompare() considers differences
+
+    const Zstring& lhsNorm = getUnicodeNormalForm(lhs);
+    const Zstring& rhsNorm = getUnicodeNormalForm(rhs);
+
+    const char* strL = lhsNorm.c_str();
+    const char* strR = rhsNorm.c_str();
+
+    const char* const strEndL = strL + lhsNorm.size();
+    const char* const strEndR = strR + rhsNorm.size();
     /*
         - compare strings after conceptually creating blocks of whitespace/numbers/text
         - implement strict weak ordering!
@@ -84,43 +195,43 @@ int cmpStringNaturalLinuxTest(const char* lhs, size_t lhsLen, const char* rhs, s
     */
     for (;;)
     {
-        if (lhs == lhsEnd || rhs == rhsEnd)
-            return static_cast<int>(lhs != lhsEnd) - static_cast<int>(rhs != rhsEnd); //"nothing" before "something"
+        if (strL == strEndL || strR == strEndR)
+            return static_cast<int>(strL != strEndL) - static_cast<int>(strR != strEndR); //"nothing" before "something"
         //note: "something" never would have been condensed to "nothing" further below => can finish evaluation here
 
-        const bool wsL = isWhiteSpace(*lhs);
-        const bool wsR = isWhiteSpace(*rhs);
+        const bool wsL = isWhiteSpace(*strL);
+        const bool wsR = isWhiteSpace(*strR);
         if (wsL != wsR)
             return static_cast<int>(!wsL) - static_cast<int>(!wsR); //whitespace before non-ws!
         if (wsL)
         {
-            ++lhs, ++rhs;
-            while (lhs != lhsEnd && isWhiteSpace(*lhs)) ++lhs;
-            while (rhs != rhsEnd && isWhiteSpace(*rhs)) ++rhs;
+            ++strL, ++strR;
+            while (strL != strEndL && isWhiteSpace(*strL)) ++strL;
+            while (strR != strEndR && isWhiteSpace(*strR)) ++strR;
             continue;
         }
 
-        const bool digitL = isDigit(*lhs);
-        const bool digitR = isDigit(*rhs);
+        const bool digitL = isDigit(*strL);
+        const bool digitR = isDigit(*strR);
         if (digitL != digitR)
             return static_cast<int>(!digitL) - static_cast<int>(!digitR); //number before chars!
         if (digitL)
         {
-            while (lhs != lhsEnd && *lhs == '0') ++lhs;
-            while (rhs != rhsEnd && *rhs == '0') ++rhs;
+            while (strL != strEndL && *strL == '0') ++strL;
+            while (strR != strEndR && *strR == '0') ++strR;
 
             int rv = 0;
-            for (;; ++lhs, ++rhs)
+            for (;; ++strL, ++strR)
             {
-                const bool endL = lhs == lhsEnd || !isDigit(*lhs);
-                const bool endR = rhs == rhsEnd || !isDigit(*rhs);
+                const bool endL = strL == strEndL || !isDigit(*strL);
+                const bool endR = strR == strEndR || !isDigit(*strR);
                 if (endL != endR)
                     return static_cast<int>(!endL) - static_cast<int>(!endR); //more digits means bigger number
                 if (endL)
                     break; //same number of digits
 
-                if (rv == 0 && *lhs != *rhs)
-                    rv = *lhs - *rhs; //found first digit difference comparing from left
+                if (rv == 0 && *strL != *strR)
+                    rv = *strL - *strR; //found first digit difference comparing from left
             }
             if (rv != 0)
                 return rv;
@@ -128,28 +239,19 @@ int cmpStringNaturalLinuxTest(const char* lhs, size_t lhsLen, const char* rhs, s
         }
 
         //compare full junks of text: consider unicode encoding!
-        const char* textBeginL = lhs++;
-        const char* textBeginR = rhs++; //current char is neither white space nor digit at this point!
-        while (lhs != lhsEnd && !isWhiteSpace(*lhs) && !isDigit(*lhs)) ++lhs;
-        while (rhs != rhsEnd && !isWhiteSpace(*rhs) && !isDigit(*rhs)) ++rhs;
+        const char* textBeginL = strL++;
+        const char* textBeginR = strR++; //current char is neither white space nor digit at this point!
+        while (strL != strEndL && !isWhiteSpace(*strL) && !isDigit(*strL)) ++strL;
+        while (strR != strEndR && !isWhiteSpace(*strR) && !isDigit(*strR)) ++strR;
 
-        const int rv = compareNoCaseUtf8(textBeginL, lhs - textBeginL, textBeginR, rhs - textBeginR);
+        const int rv = compareNoCaseUtf8(textBeginL, strL - textBeginL, textBeginR, strR - textBeginR);
         if (rv != 0)
             return rv;
     }
-}
-
 
-namespace
-{
 }
 
 
-int CmpNaturalSort::operator()(const Zchar* lhs, size_t lhsLen, const Zchar* rhs, size_t rhsLen) const
-{
-    //auto strL = utfTo<std::string>(Zstring(lhs, lhsLen));
-    //auto strR = utfTo<std::string>(Zstring(rhs, rhsLen));
-    //return cmpStringNaturalLinux(strL.c_str(), strL.size(), strR.c_str(), strR.size());
-    return cmpStringNaturalLinux(lhs, lhsLen, rhs, rhsLen);
-
-}
\ No newline at end of file
+warn_static("clean up implementation of these two:")
+//template <> inline bool isWhiteSpace(char c)
+//template <> inline bool isWhiteSpace(wchar_t c)
diff --git a/zen/zstring.h b/zen/zstring.h
index 7fa21335..20cf968d 100755
--- a/zen/zstring.h
+++ b/zen/zstring.h
@@ -14,6 +14,7 @@
     #define Zstr(x) x
     const Zchar FILE_NAME_SEPARATOR = '/';
 
+
 //"The reason for all the fuss above" - Loki/SmartPtr
 //a high-performance string for interfacing with native OS APIs in multithreaded contexts
 using Zstring = zen::Zbase<Zchar>;
@@ -22,43 +23,71 @@ using Zstring = zen::Zbase<Zchar>;
 using Zstringw = zen::Zbase<wchar_t>;
 
 
-//Compare filepaths: Windows/OS X does NOT distinguish between upper/lower-case, while Linux DOES
-struct CmpFilePath
-{
-    int operator()(const Zchar* lhs, size_t lhsLen, const Zchar* rhs, size_t rhsLen) const;
-};
+//Caveat: don't expect input/output string sizes to match:
+// - different UTF-8 encoding length of upper-case chars
+// - different number of upper case chars (e.g. "ß" => "SS" on macOS)
+// - output is Unicode-normalized
+Zstring makeUpperCopy(const Zstring& str);
 
-struct CmpNaturalSort
-{
-    int operator()(const Zchar* lhs, size_t lhsLen, const Zchar* rhs, size_t rhsLen) const;
-};
+//Windows, Linux: precomposed
+//macOS: decomposed
+Zstring getUnicodeNormalForm(const Zstring& str);
 
+Zstring replaceCpyAsciiNoCase(const Zstring& str, const Zstring& oldTerm, const Zstring& newTerm);
 
-struct LessFilePath
-{
-    template <class S> //don't support heterogenous input! => use as container predicate only!
-    bool operator()(const S& lhs, const S& rhs) const { using namespace zen; return CmpFilePath()(strBegin(lhs), strLength(lhs), strBegin(rhs), strLength(rhs)) < 0; }
-};
+//------------------------------------------------------------------------------------------
+//inline
+//int compareNoCase(const Zstring& lhs, const Zstring& rhs)
+//{
+//    return zen::compareString(makeUpperCopy(lhs), makeUpperCopy(rhs));
+//    //avoid eager optimization bugs: e.g. "if (isAsciiString()) compareAsciiNoCase()" might model a different order!
+//}
+
+inline bool equalNoCase(const Zstring& lhs, const Zstring& rhs) { return makeUpperCopy(lhs) == makeUpperCopy(rhs); }
 
-struct LessNaturalSort
+struct ZstringNoCase //use as STL container key: avoid needless upper-case conversions during std::map<>::find()
 {
-    template <class S> //don't support heterogenous input! => use as container predicate only!
-    bool operator()(const S& lhs, const S& rhs) const { using namespace zen; return CmpNaturalSort()(strBegin(lhs), strLength(lhs), strBegin(rhs), strLength(rhs)) < 0; }
+        ZstringNoCase(const Zstring& str) : upperCase(makeUpperCopy(str)) {}
+        Zstring upperCase;
 };
+inline bool operator<(const ZstringNoCase& lhs, const ZstringNoCase& rhs) { return lhs.upperCase < rhs.upperCase; } 
+
+//struct LessNoCase { bool operator()(const Zstring& lhs, const Zstring& rhs) const { return compareNoCase(lhs, rhs) < 0; } };
+
+//------------------------------------------------------------------------------------------
+
+//Compare *local* file paths:
+//  Windows: igore case
+//  Linux:   byte-wise comparison
+//  macOS:   igore case + Unicode normalization forms
+int compareLocalPath(const Zstring& lhs, const Zstring& rhs);
+
+inline bool equalLocalPath(const Zstring& lhs, const Zstring& rhs) { return compareLocalPath(lhs, rhs) == 0;  }
 
+struct LessLocalPath { bool operator()(const Zstring& lhs, const Zstring& rhs) const { return compareLocalPath(lhs, rhs) < 0;  } };
 
-template <class S>
-S makeUpperCopy(S str);
+//------------------------------------------------------------------------------------------
+int compareNatural(const Zstring& lhs, const Zstring& rhs);
 
+struct LessNaturalSort { bool operator()(const Zstring& lhs, const Zstring rhs) const { return compareNatural(lhs, rhs) < 0; } };
+//------------------------------------------------------------------------------------------
+
+warn_static("get rid:")
+inline int compareFilePath(const Zstring& lhs, const Zstring& rhs) { return compareLocalPath(lhs, rhs); }
+
+inline bool equalFilePath(const Zstring& lhs, const Zstring& rhs) { return compareLocalPath(lhs, rhs) == 0; }
+
+struct LessFilePath { bool operator()(const Zstring& lhs, const Zstring& rhs) const { return compareLocalPath(lhs, rhs) < 0; } };
+//------------------------------------------------------------------------------------------
 
-template <class S, class T> inline
-bool equalFilePath(const S& lhs, const T& rhs) { using namespace zen; return strEqual(lhs, rhs, CmpFilePath());  }
 
 
 inline
 Zstring appendSeparator(Zstring path) //support rvalue references!
 {
-    return zen::endsWith(path, FILE_NAME_SEPARATOR) ? path : (path += FILE_NAME_SEPARATOR); //returning a by-value parameter implicitly converts to r-value!
+    if (!zen::endsWith(path, FILE_NAME_SEPARATOR))
+        path += FILE_NAME_SEPARATOR;
+    return path; //returning a by-value parameter => RVO if possible, r-value otherwise!
 }
 
 
@@ -82,12 +111,7 @@ Zstring getFileExtension(const Zstring& filePath)
 }
 
 
-template <class S, class T, class U>
-S ciReplaceCpy(const S& str, const T& oldTerm, const U& newTerm);
-
-
-
-//common unicode sequences
+//common unicode characters
 const wchar_t EM_DASH = L'\u2014';
 const wchar_t EN_DASH = L'\u2013';
 const wchar_t* const SPACED_DASH = L" \u2013 "; //using 'EN DASH'
@@ -99,89 +123,6 @@ const wchar_t MULT_SIGN = L'\u00D7'; //fancy "x"
 
 
 
-
-
-//################################# inline implementation ########################################
-inline
-void makeUpperInPlace(wchar_t* str, size_t strLen)
-{
-    std::for_each(str, str + strLen, [](wchar_t& c) { c = std::towupper(c); }); //locale-dependent!
-}
-
-
-inline
-void makeUpperInPlace(char* str, size_t strLen)
-{
-    std::for_each(str, str + strLen, [](char& c) { c = std::toupper(static_cast<unsigned char>(c)); }); //locale-dependent!
-    //result of toupper() is an unsigned char mapped to int range: the char representation is in the last 8 bits and we need not care about signedness!
-    //this should work for UTF-8, too: all chars >= 128 are mapped upon themselves!
-}
-
-
-template <class S> inline
-S makeUpperCopy(S str)
-{
-    const size_t len = str.length(); //we assert S is a string type!
-    if (len > 0)
-        makeUpperInPlace(&*str.begin(), len);
-
-    return str;
-}
-
-
-inline
-int CmpFilePath::operator()(const Zchar* lhs, size_t lhsLen, const Zchar* rhs, size_t rhsLen) const
-{
-    assert(std::find(lhs, lhs + lhsLen, 0) == lhs + lhsLen); //don't expect embedded nulls!
-    assert(std::find(rhs, rhs + rhsLen, 0) == rhs + rhsLen); //
-
-    const int rv = std::strncmp(lhs, rhs, std::min(lhsLen, rhsLen));
-    if (rv != 0)
-        return rv;
-    return static_cast<int>(lhsLen) - static_cast<int>(rhsLen);
-}
-
-
-template <class S, class T, class U> inline
-S ciReplaceCpy(const S& str, const T& oldTerm, const U& newTerm)
-{
-    using namespace zen;
-    static_assert(std::is_same_v<GetCharTypeT<S>, GetCharTypeT<T>>);
-    static_assert(std::is_same_v<GetCharTypeT<T>, GetCharTypeT<U>>);
-    const size_t oldLen = strLength(oldTerm);
-    if (oldLen == 0)
-        return str;
-
-    const S strU = makeUpperCopy(str); //S required to be a string class
-    const S oldU = makeUpperCopy<S>(oldTerm); //[!] T not required to be a string class
-    assert(strLength(strU) == strLength(str    ));
-    assert(strLength(oldU) == strLength(oldTerm));
-
-    const auto* const newBegin = strBegin(newTerm);
-    const auto* const newEnd   = newBegin + strLength(newTerm);
-
-    S output;
-
-    for (size_t pos = 0;;)
-    {
-        const auto itFound = std::search(strU.begin() + pos, strU.end(),
-                                         oldU.begin(), oldU.end());
-        if (itFound == strU.end() && pos == 0)
-            return str; //optimize "oldTerm not found": return ref-counted copy
-
-        impl::stringAppend(output, str.begin() + pos, str.begin() + (itFound - strU.begin()));
-        if (itFound == strU.end())
-            return output;
-
-        impl::stringAppend(output, newBegin, newEnd);
-        pos = (itFound - strU.begin()) + oldLen;
-    }
-}
-
-//expose for unit tests
-int cmpStringNaturalLinuxTest(const char* lhs, size_t lhsLen, const char* rhs, size_t rhsLen);
-inline int cmpStringNaturalLinux(const char* lhs, size_t lhsLen, const char* rhs, size_t rhsLen) { return cmpStringNaturalLinuxTest(lhs, lhsLen, rhs, rhsLen); }
-
 //---------------------------------------------------------------------------
 //ZEN macro consistency checks: