Merge branch '11.7' into 'master'11.7

add upstream 11.7

See merge request opensource-tracking/FreeFileSync!31

29 files changed, 313 insertions, 379 deletions

diff --git a/zen/basic_math.h b/zen/basic_math.h
index a4feb83e..944a0f53 100644
--- a/zen/basic_math.h
+++ b/zen/basic_math.h
@@ -111,14 +111,14 @@ std::pair<InputIterator, InputIterator> minMaxElement(InputIterator first, Input
             }
         }
     }
-    return { lowest, largest };
+    return {lowest, largest};
 }
 
 
 template <class InputIterator> inline
 std::pair<InputIterator, InputIterator> minMaxElement(InputIterator first, InputIterator last)
 {
-    return minMaxElement(first, last, std::less<typename std::iterator_traits<InputIterator>::value_type>());
+    return minMaxElement(first, last, std::less());
 }
 */
 
@@ -152,10 +152,10 @@ template <class N, class D> inline
 auto intDivRound(N num, D den)
 {
     using namespace zen;
-    static_assert(IsInteger<N>::value && IsInteger<D>::value);
-    static_assert(IsSignedInt<N>::value == IsSignedInt<D>::value); //until further
+    static_assert(IsIntegerV<N>&& IsIntegerV<D>);
+    static_assert(IsSignedIntV<N> == IsSignedIntV<D>); //until further
     assert(den != 0);
-    if constexpr (IsSignedInt<N>::value)
+    if constexpr (IsSignedIntV<N>)
     {
         if ((num < 0) != (den < 0))
             return (num - den / 2) / den;
@@ -168,10 +168,10 @@ template <class N, class D> inline
 auto intDivCeil(N num, D den)
 {
     using namespace zen;
-    static_assert(IsInteger<N>::value && IsInteger<D>::value);
-    static_assert(IsSignedInt<N>::value == IsSignedInt<D>::value); //until further
+    static_assert(IsIntegerV<N>&& IsIntegerV<D>);
+    static_assert(IsSignedIntV<N> == IsSignedIntV<D>); //until further
     assert(den != 0);
-    if constexpr (IsSignedInt<N>::value)
+    if constexpr (IsSignedIntV<N>)
     {
         if ((num < 0) != (den < 0))
             return num / den;
@@ -187,10 +187,10 @@ template <class N, class D> inline
 auto intDivFloor(N num, D den)
 {
     using namespace zen;
-    static_assert(IsInteger<N>::value && IsInteger<D>::value);
-    static_assert(IsSignedInt<N>::value == IsSignedInt<D>::value); //until further
+    static_assert(IsIntegerV<N>&& IsIntegerV<D>);
+    static_assert(IsSignedIntV<N> == IsSignedIntV<D>); //until further
     assert(den != 0);
-    if constexpr (IsSignedInt<N>::value)
+    if constexpr (IsSignedIntV<N>)
     {
         if ((num < 0) != (den < 0))
         {
diff --git a/zen/dir_watcher.cpp b/zen/dir_watcher.cpp
index dc416b34..191ffd64 100644
--- a/zen/dir_watcher.cpp
+++ b/zen/dir_watcher.cpp
@@ -9,7 +9,6 @@
 #include <set>
 #include "thread.h"
 #include "scope_guard.h"
-//#include "basic_math.h"
 
     #include <map>
     #include <sys/inotify.h>
@@ -34,7 +33,7 @@ DirWatcher::DirWatcher(const Zstring& dirPath) : //throw FileError
     pimpl_(std::make_unique<Impl>())
 {
     //get all subdirectories
-    std::vector<Zstring> fullFolderList { baseDirPath_ };
+    std::vector<Zstring> fullFolderList {baseDirPath_};
     {
         std::function<void (const Zstring& path)> traverse;
 
@@ -102,7 +101,7 @@ DirWatcher::~DirWatcher()
 
 std::vector<DirWatcher::Change> DirWatcher::fetchChanges(const std::function<void()>& requestUiUpdate, std::chrono::milliseconds cbInterval) //throw FileError
 {
-    std::vector<std::byte> buffer(512 * (sizeof(struct ::inotify_event) + NAME_MAX + 1));
+    std::vector<std::byte> buffer(512 * (sizeof(inotify_event) + NAME_MAX + 1));
 
     ssize_t bytesRead = 0;
     do
@@ -125,7 +124,7 @@ std::vector<DirWatcher::Change> DirWatcher::fetchChanges(const std::function<voi
     ssize_t bytePos = 0;
     while (bytePos < bytesRead)
     {
-        struct ::inotify_event& evt = reinterpret_cast<struct ::inotify_event&>(buffer[bytePos]);
+        inotify_event& evt = reinterpret_cast<inotify_event&>(buffer[bytePos]);
 
         if (evt.len != 0) //exclude case: deletion of "self", already reported by parent directory watch
         {
@@ -138,18 +137,18 @@ std::vector<DirWatcher::Change> DirWatcher::fetchChanges(const std::function<voi
 
                 if ((evt.mask & IN_CREATE) ||
                     (evt.mask & IN_MOVED_TO))
-                    output.push_back({ ChangeType::create, itemPath });
+                    output.push_back({ChangeType::create, itemPath});
                 else if ((evt.mask & IN_MODIFY) ||
                          (evt.mask & IN_CLOSE_WRITE))
-                    output.push_back({ ChangeType::update, itemPath });
+                    output.push_back({ChangeType::update, itemPath});
                 else if ((evt.mask & IN_DELETE     ) ||
                          (evt.mask & IN_DELETE_SELF) ||
                          (evt.mask & IN_MOVE_SELF  ) ||
                          (evt.mask & IN_MOVED_FROM))
-                    output.push_back({ ChangeType::remove, itemPath });
+                    output.push_back({ChangeType::remove, itemPath});
             }
         }
-        bytePos += sizeof(struct ::inotify_event) + evt.len;
+        bytePos += sizeof(inotify_event) + evt.len;
     }
 
     return output;
diff --git a/zen/error_log.h b/zen/error_log.h
index 6d9f80ae..a24dfe5a 100644
--- a/zen/error_log.h
+++ b/zen/error_log.h
@@ -68,7 +68,7 @@ private:
 inline
 void ErrorLog::logMsg(const std::wstring& msg, MessageType type)
 {
-    entries_.push_back({ std::time(nullptr), type, utfTo<Zstringc>(msg) });
+    entries_.push_back({std::time(nullptr), type, utfTo<Zstringc>(msg)});
 }
 
 
diff --git a/zen/file_access.cpp b/zen/file_access.cpp
index 4c9af652..fb770f19 100644
--- a/zen/file_access.cpp
+++ b/zen/file_access.cpp
@@ -12,7 +12,6 @@
 #include "file_traverser.h"
 #include "scope_guard.h"
 #include "symlink_target.h"
-#include "file_id_def.h"
 #include "file_io.h"
 #include "crc.h"
 #include "guid.h"
@@ -45,7 +44,7 @@ std::optional<PathComponents> zen::parsePathComponents(const Zstring& itemPath)
                     Zstring relPath(it + 1, itemPathFmt.end());
                     trim(relPath, true, true, [](Zchar c) { return c == FILE_NAME_SEPARATOR; });
 
-                    return PathComponents({ rootPath, relPath });
+                    return PathComponents({rootPath, relPath});
                 }
         return {};
     };
@@ -100,7 +99,7 @@ std::optional<Zstring> zen::getParentFolderPath(const Zstring& itemPath)
 
 ItemType zen::getItemType(const Zstring& itemPath) //throw FileError
 {
-    struct ::stat itemInfo = {};
+    struct stat itemInfo = {};
     if (::lstat(itemPath.c_str(), &itemInfo) != 0)
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(itemPath)), "lstat");
 
@@ -153,7 +152,7 @@ std::optional<ItemType> zen::itemStillExists(const Zstring& itemPath) //throw Fi
 bool zen::fileAvailable(const Zstring& filePath) //noexcept
 {
     //symbolic links (broken or not) are also treated as existing files!
-    struct ::stat fileInfo = {};
+    struct stat fileInfo = {};
     if (::stat(filePath.c_str(), &fileInfo) == 0) //follow symlinks!
         return S_ISREG(fileInfo.st_mode);
     return false;
@@ -163,7 +162,7 @@ bool zen::fileAvailable(const Zstring& filePath) //noexcept
 bool zen::dirAvailable(const Zstring& dirPath) //noexcept
 {
     //symbolic links (broken or not) are also treated as existing directories!
-    struct ::stat dirInfo = {};
+    struct stat dirInfo = {};
     if (::stat(dirPath.c_str(), &dirInfo) == 0) //follow symlinks!
         return S_ISDIR(dirInfo.st_mode);
     return false;
@@ -177,29 +176,22 @@ namespace
 
 int64_t zen::getFreeDiskSpace(const Zstring& path) //throw FileError, returns < 0 if not available
 {
-    struct ::statfs info = {};
-    if (::statfs(path.c_str(), &info) != 0)
+    struct statfs info = {};
+    if (::statfs(path.c_str(), &info) != 0) //follows symlinks!
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot determine free disk space for %x."), L"%x", fmtPath(path)), "statfs");
+    //Linux: "Fields that are undefined for a particular file system are set to 0."
+    //macOS: "Fields that are undefined for a particular file system are set to -1." - mkay :>
+    if (makeSigned(info.f_bsize)  <= 0 ||
+        makeSigned(info.f_bavail) <= 0)
+        return -1;
 
     return static_cast<int64_t>(info.f_bsize) * info.f_bavail;
 }
 
 
-VolumeId zen::getVolumeId(const Zstring& itemPath) //throw FileError
-{
-    struct ::stat fileInfo = {};
-    if (::stat(itemPath.c_str(), &fileInfo) != 0)
-        THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(itemPath)), "stat");
-
-    warn_static("NOT STABLE!")
-
-    return fileInfo.st_dev;
-}
-
-
 uint64_t zen::getFileSize(const Zstring& filePath) //throw FileError
 {
-    struct ::stat fileInfo = {};
+    struct stat fileInfo = {};
     if (::stat(filePath.c_str(), &fileInfo) != 0)
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(filePath)), "stat");
 
@@ -207,6 +199,8 @@ uint64_t zen::getFileSize(const Zstring& filePath) //throw FileError
 }
 
 
+
+
 Zstring zen::getTempFolderPath() //throw FileError
 {
     if (const char* tempPath = ::getenv("TMPDIR")) //no extended error reporting
@@ -336,15 +330,15 @@ void moveAndRenameFileSub(const Zstring& pathFrom, const Zstring& pathTo, bool r
     //macOS: no solution https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man2/rename.2.html
     if (!replaceExisting)
     {
-        struct ::stat infoSrc = {};
-        if (::lstat(pathFrom.c_str(), &infoSrc) != 0)
+        struct stat sourceInfo = {};
+        if (::lstat(pathFrom.c_str(), &sourceInfo) != 0)
             THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(pathFrom)), "stat");
 
-        struct ::stat infoTrg = {};
-        if (::lstat(pathTo.c_str(), &infoTrg) == 0)
+        struct stat targetInfo = {};
+        if (::lstat(pathTo.c_str(), &targetInfo) == 0)
         {
-            if (infoSrc.st_dev != infoTrg.st_dev ||
-                infoSrc.st_ino != infoTrg.st_ino)
+            if (sourceInfo.st_dev != targetInfo.st_dev ||
+                sourceInfo.st_ino != targetInfo.st_ino)
                 throwException(EEXIST); //that's what we're really here for
             //else: continue with a rename in case
             //caveat: if we have a hardlink referenced by two different paths, the source one will be unlinked => fine, but not exactly a "rename"...
@@ -376,7 +370,7 @@ void zen::moveAndRenameItem(const Zstring& pathFrom, const Zstring& pathTo, bool
 
 namespace
 {
-void setWriteTimeNative(const Zstring& itemPath, const struct ::timespec& modTime, ProcSymlink procSl) //throw FileError
+void setWriteTimeNative(const Zstring& itemPath, const timespec& modTime, ProcSymlink procSl) //throw FileError
 {
     /*
     [2013-05-01] sigh, we can't use utimensat() on NTFS volumes on Ubuntu: silent failure!!! what morons are programming this shit???
@@ -388,12 +382,12 @@ void setWriteTimeNative(const Zstring& itemPath, const struct ::timespec& modTim
         => let's give utimensat another chance:
         using open()/futimens() for regular files and utimensat(AT_SYMLINK_NOFOLLOW) for symlinks is consistent with "cp" and "touch"!
     */
-    struct ::timespec newTimes[2] = {};
+    timespec newTimes[2] = {};
     newTimes[0].tv_sec = ::time(nullptr); //access time; using UTIME_OMIT for tv_nsec would trigger even more bugs: https://freefilesync.org/forum/viewtopic.php?t=1701
     newTimes[1] = modTime; //modification time
     //test: even modTime == 0 is correctly applied (no NOOP!) test2: same behavior for "utime()"
 
-    if (procSl == ProcSymlink::FOLLOW)
+    if (procSl == ProcSymlink::follow)
     {
         //hell knows why files on gvfs-mounted Samba shares fail to open(O_WRONLY) returning EOPNOTSUPP:
         //https://freefilesync.org/forum/viewtopic.php?t=2803 => utimensat() works (but not for gvfs SFTP)
@@ -422,10 +416,8 @@ void setWriteTimeNative(const Zstring& itemPath, const struct ::timespec& modTim
 
 void zen::setFileTime(const Zstring& filePath, time_t modTime, ProcSymlink procSl) //throw FileError
 {
-    struct ::timespec writeTime = {};
-    writeTime.tv_sec = modTime;
-    setWriteTimeNative(filePath, writeTime, procSl); //throw FileError
-
+    setWriteTimeNative(filePath, timetToNativeFileTime(modTime),
+                       procSl); //throw FileError
 }
 
 
@@ -442,7 +434,7 @@ namespace
 void copySecurityContext(const Zstring& source, const Zstring& target, ProcSymlink procSl) //throw FileError
 {
     security_context_t contextSource = nullptr;
-    const int rv = procSl == ProcSymlink::FOLLOW ?
+    const int rv = procSl == ProcSymlink::follow ?
                    ::getfilecon (source.c_str(), &contextSource) :
                    ::lgetfilecon(source.c_str(), &contextSource);
     if (rv < 0)
@@ -457,7 +449,7 @@ void copySecurityContext(const Zstring& source, const Zstring& target, ProcSymli
 
     {
         security_context_t contextTarget = nullptr;
-        const int rv2 = procSl == ProcSymlink::FOLLOW ?
+        const int rv2 = procSl == ProcSymlink::follow ?
                         ::getfilecon(target.c_str(), &contextTarget) :
                         ::lgetfilecon(target.c_str(), &contextTarget);
         if (rv2 < 0)
@@ -475,7 +467,7 @@ void copySecurityContext(const Zstring& source, const Zstring& target, ProcSymli
         }
     }
 
-    const int rv3 = procSl == ProcSymlink::FOLLOW ?
+    const int rv3 = procSl == ProcSymlink::follow ?
                     ::setfilecon(target.c_str(), contextSource) :
                     ::lsetfilecon(target.c_str(), contextSource);
     if (rv3 < 0)
@@ -493,8 +485,8 @@ void zen::copyItemPermissions(const Zstring& sourcePath, const Zstring& targetPa
     copySecurityContext(sourcePath, targetPath, procSl); //throw FileError
 #endif
 
-    struct ::stat fileInfo = {};
-    if (procSl == ProcSymlink::FOLLOW)
+    struct stat fileInfo = {};
+    if (procSl == ProcSymlink::follow)
     {
         if (::stat(sourcePath.c_str(), &fileInfo) != 0)
             THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read permissions of %x."), L"%x", fmtPath(sourcePath)), "stat");
@@ -614,22 +606,22 @@ void zen::copySymlink(const Zstring& sourcePath, const Zstring& targetPath) //th
     catch (FileError&) {});
 
     //file times: essential for syncing a symlink: enforce this! (don't just try!)
-    struct ::stat sourceInfo = {};
+    struct stat sourceInfo = {};
     if (::lstat(sourcePath.c_str(), &sourceInfo) != 0)
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(sourcePath)), "lstat");
 
-    setWriteTimeNative(targetPath, sourceInfo.st_mtim, ProcSymlink::DIRECT); //throw FileError
+    setWriteTimeNative(targetPath, sourceInfo.st_mtim, ProcSymlink::direct); //throw FileError
 }
 
 
 FileCopyResult zen::copyNewFile(const Zstring& sourceFile, const Zstring& targetFile, //throw FileError, ErrorTargetExisting, (ErrorFileLocked), X
-                                const IOCallback& notifyUnbufferedIO /*throw X*/)
+                                const IoCallback& notifyUnbufferedIO /*throw X*/)
 {
     int64_t totalUnbufferedIO = 0;
 
     FileInput fileIn(sourceFile, IOCallbackDivider(notifyUnbufferedIO, totalUnbufferedIO)); //throw FileError, (ErrorFileLocked -> Windows-only)
 
-    struct ::stat sourceInfo = {};
+    struct stat sourceInfo = {};
     if (::fstat(fileIn.getHandle(), &sourceInfo) != 0)
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(sourceFile)), "fstat");
 
@@ -637,7 +629,7 @@ FileCopyResult zen::copyNewFile(const Zstring& sourceFile, const Zstring& target
     //it seems we don't need S_IWUSR, not even for the setFileTime() below! (tested with source file having different user/group!)
 
     //=> need copyItemPermissions() only for "chown" and umask-agnostic permissions
-    const int fdTarget = ::open(targetFile.c_str(), O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC, mode);
+    const int fdTarget = ::open(targetFile.c_str(), O_CREAT | O_EXCL | O_WRONLY | O_CLOEXEC, mode);
     if (fdTarget == -1)
     {
         const int ec = errno; //copy before making other system calls!
@@ -659,7 +651,7 @@ FileCopyResult zen::copyNewFile(const Zstring& sourceFile, const Zstring& target
     //flush intermediate buffers before fiddling with the raw file handle
     fileOut.flushBuffers(); //throw FileError, X
 
-    struct ::stat targetInfo = {};
+    struct stat targetInfo = {};
     if (::fstat(fileOut.getHandle(), &targetInfo) != 0)
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(targetFile)), "fstat");
 
@@ -673,12 +665,12 @@ FileCopyResult zen::copyNewFile(const Zstring& sourceFile, const Zstring& target
     std::optional<FileError> errorModTime;
     try
     {
-        //we cannot set the target file times (::futimes) while the file descriptor is still open after a write operation:
-        //this triggers bugs on samba shares where the modification time is set to current time instead.
-        //Linux: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=340236
-        //       http://comments.gmane.org/gmane.linux.file-systems.cifs/2854
-        //OS X:  https://freefilesync.org/forum/viewtopic.php?t=356
-        setWriteTimeNative(targetFile, sourceInfo.st_mtim, ProcSymlink::FOLLOW); //throw FileError
+        /*  we cannot set the target file times (::futimes) while the file descriptor is still open after a write operation:
+            this triggers bugs on Samba shares where the modification time is set to current time instead.
+            Linux: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=340236
+                    http://comments.gmane.org/gmane.linux.file-systems.cifs/2854
+            macOS: https://freefilesync.org/forum/viewtopic.php?t=356             */
+        setWriteTimeNative(targetFile, sourceInfo.st_mtim, ProcSymlink::follow); //throw FileError
     }
     catch (const FileError& e)
     {
@@ -687,9 +679,9 @@ FileCopyResult zen::copyNewFile(const Zstring& sourceFile, const Zstring& target
 
     FileCopyResult result;
     result.fileSize = sourceInfo.st_size;
-    result.modTime = sourceInfo.st_mtim.tv_sec; //
-    result.sourceFileId = generateFileId(sourceInfo);
-    result.targetFileId = generateFileId(targetInfo);
+    result.sourceModTime = sourceInfo.st_mtim;
+    result.sourceFileIdx = sourceInfo.st_ino;
+    result.targetFileIdx = targetInfo.st_ino;
     result.errorModTime = errorModTime;
     return result;
 }
diff --git a/zen/file_access.h b/zen/file_access.h
index a3fa56d7..f3ea6c00 100644
--- a/zen/file_access.h
+++ b/zen/file_access.h
@@ -10,9 +10,8 @@
 #include <functional>
 #include "zstring.h"
 #include "file_error.h"
-#include "file_id_def.h"
-#include "serialize.h"
-
+#include "serialize.h" //IoCallback
+    #include <sys/stat.h>
 
 namespace zen
 {
@@ -31,6 +30,21 @@ std::optional<Zstring> getParentFolderPath(const Zstring& itemPath);
 bool fileAvailable(const Zstring& filePath); //noexcept
 bool dirAvailable (const Zstring& dirPath ); //
 
+//FAT/FAT32: "Why does the timestamp of a file *increase* by up to 2 seconds when I copy it to a USB thumb drive?"
+const int FAT_FILE_TIME_PRECISION_SEC = 2; //https://devblogs.microsoft.com/oldnewthing/?p=83
+//https://web.archive.org/web/20141127143832/http://support.microsoft.com/kb/127830
+
+using FileIndex = ino_t;
+using FileTimeNative = timespec;
+
+inline time_t nativeFileTimeToTimeT(const timespec& ft) { return ft.tv_sec; } //follow Windows Explorer and always round down!
+inline timespec timetToNativeFileTime(time_t utcTime)
+{
+    timespec natTime = {};
+    natTime.tv_sec = utcTime;
+    return natTime;
+}
+
 enum class ItemType
 {
     file,
@@ -47,14 +61,13 @@ std::optional<ItemType> itemStillExists(const Zstring& itemPath); //throw FileEr
 
 enum class ProcSymlink
 {
-    DIRECT,
-    FOLLOW
+    direct,
+    follow
 };
 void setFileTime(const Zstring& filePath, time_t modTime, ProcSymlink procSl); //throw FileError
 
 //symlink handling: follow
 int64_t getFreeDiskSpace(const Zstring& path); //throw FileError, returns < 0 if not available
-VolumeId getVolumeId(const Zstring& itemPath); //throw FileError
 uint64_t getFileSize(const Zstring& filePath); //throw FileError
 
 //get per-user directory designated for temporary files:
@@ -87,16 +100,15 @@ void copySymlink(const Zstring& sourcePath, const Zstring& targetPath); //throw
 struct FileCopyResult
 {
     uint64_t fileSize = 0;
-    time_t modTime = 0; //number of seconds since Jan. 1st 1970 UTC
-    FileId sourceFileId;
-    FileId targetFileId;
+    FileTimeNative sourceModTime = {};
+    FileIndex sourceFileIdx = 0;
+    FileIndex targetFileIdx = 0;
     std::optional<FileError> errorModTime; //failure to set modification time
 };
 
 FileCopyResult copyNewFile(const Zstring& sourceFile, const Zstring& targetFile, //throw FileError, ErrorTargetExisting, ErrorFileLocked, X
                            //accummulated delta != file size! consider ADS, sparse, compressed files
-                           const IOCallback& notifyUnbufferedIO /*throw X*/);
-
+                           const IoCallback& notifyUnbufferedIO /*throw X*/);
 }
 
 #endif //FILE_ACCESS_H_8017341345614857
diff --git a/zen/file_id_def.h b/zen/file_id_def.h
deleted file mode 100644
index d2d104d5..00000000
--- a/zen/file_id_def.h
+++ /dev/null
@@ -1,46 +0,0 @@
-// *****************************************************************************
-// * This file is part of the FreeFileSync project. It is distributed under    *
-// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0          *
-// * Copyright (C) Zenju (zenju AT freefilesync DOT org) - All Rights Reserved *
-// *****************************************************************************
-
-#ifndef FILE_ID_DEF_H_013287632486321493
-#define FILE_ID_DEF_H_013287632486321493
-
-    #include <sys/stat.h>
-
-
-namespace zen
-{
-namespace impl { typedef struct ::stat StatDummy; } //sigh...
-
-using VolumeId  = decltype(impl::StatDummy::st_dev);
-using FileIndex = decltype(impl::StatDummy::st_ino);
-
-
-struct FileId //always available on Linux, and *generally* available on Windows)
-{
-    FileId() {}
-    FileId(VolumeId volId, FileIndex fIdx) : volumeId(volId), fileIndex(fIdx)
-    {
-        if (volId == 0 || fIdx == 0)
-        {
-            volumeId  = 0;
-            fileIndex = 0;
-        }
-    }
-    VolumeId  volumeId  = 0;
-    FileIndex fileIndex = 0;
-
-    bool operator==(const FileId&) const = default;
-};
-
-
-inline
-FileId generateFileId(const struct ::stat& fileInfo)
-{
-    return FileId(fileInfo.st_dev, fileInfo.st_ino);
-}
-}
-
-#endif //FILE_ID_DEF_H_013287632486321493
diff --git a/zen/file_io.cpp b/zen/file_io.cpp
index e081335d..f575a366 100644
--- a/zen/file_io.cpp
+++ b/zen/file_io.cpp
@@ -41,7 +41,7 @@ namespace
 FileBase::FileHandle openHandleForRead(const Zstring& filePath) //throw FileError, ErrorFileLocked
 {
     //caveat: check for file types that block during open(): character device, block device, named pipe
-    struct ::stat fileInfo = {};
+    struct stat fileInfo = {};
     if (::stat(filePath.c_str(), &fileInfo) == 0) //follows symlinks
     {
         if (!S_ISREG(fileInfo.st_mode) &&
@@ -74,11 +74,11 @@ FileBase::FileHandle openHandleForRead(const Zstring& filePath) //throw FileErro
 }
 
 
-FileInput::FileInput(FileHandle handle, const Zstring& filePath, const IOCallback& notifyUnbufferedIO) :
+FileInput::FileInput(FileHandle handle, const Zstring& filePath, const IoCallback& notifyUnbufferedIO) :
     FileBase(handle, filePath), notifyUnbufferedIO_(notifyUnbufferedIO) {}
 
 
-FileInput::FileInput(const Zstring& filePath, const IOCallback& notifyUnbufferedIO) :
+FileInput::FileInput(const Zstring& filePath, const IoCallback& notifyUnbufferedIO) :
     FileBase(openHandleForRead(filePath), filePath), //throw FileError, ErrorFileLocked
     notifyUnbufferedIO_(notifyUnbufferedIO)
 {
@@ -166,8 +166,13 @@ FileBase::FileHandle openHandleForWrite(const Zstring& filePath) //throw FileErr
 {
     //checkForUnsupportedType(filePath); -> not needed, open() + O_WRONLY should fail fast
 
-    const int fdFile = ::open(filePath.c_str(), O_WRONLY | O_CREAT | O_CLOEXEC | /*access == FileOutput::ACC_OVERWRITE ? O_TRUNC : */ O_EXCL,
-                              S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH); //0666 => umask will be applied implicitly!
+    const mode_t lockFileMode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH; //0666 => umask will be applied implicitly!
+
+    //O_EXCL contains a race condition on NFS file systems: https://linux.die.net/man/2/open
+    const int fdFile = ::open(filePath.c_str(), //const char* pathname
+                              O_CREAT |         //int flags     
+                              /*access == FileOutput::ACC_OVERWRITE ? O_TRUNC : */ O_EXCL | O_WRONLY  | O_CLOEXEC, 
+                              lockFileMode);    //mode_t mode
     if (fdFile == -1)
     {
         const int ec = errno; //copy before making other system calls!
@@ -185,13 +190,13 @@ FileBase::FileHandle openHandleForWrite(const Zstring& filePath) //throw FileErr
 }
 
 
-FileOutput::FileOutput(FileHandle handle, const Zstring& filePath, const IOCallback& notifyUnbufferedIO) :
+FileOutput::FileOutput(FileHandle handle, const Zstring& filePath, const IoCallback& notifyUnbufferedIO) :
     FileBase(handle, filePath), notifyUnbufferedIO_(notifyUnbufferedIO)
 {
 }
 
 
-FileOutput::FileOutput(const Zstring& filePath, const IOCallback& notifyUnbufferedIO) :
+FileOutput::FileOutput(const Zstring& filePath, const IoCallback& notifyUnbufferedIO) :
     FileBase(openHandleForWrite(filePath), filePath), notifyUnbufferedIO_(notifyUnbufferedIO) {} //throw FileError, ErrorTargetExisting
 
 
@@ -298,8 +303,8 @@ void FileOutput::reserveSpace(uint64_t expectedSize) //throw FileError
 
     //don't use ::posix_fallocate which uses horribly inefficient fallback if FS doesn't support it (EOPNOTSUPP) and changes files size!
     //FALLOC_FL_KEEP_SIZE => allocate only, file size is NOT changed!
-    if (::fallocate(getHandle(),         //int fd,
-                    FALLOC_FL_KEEP_SIZE, //int mode,
+    if (::fallocate(getHandle(),         //int fd
+                    FALLOC_FL_KEEP_SIZE, //int mode
                     0,                   //off_t offset
                     expectedSize) != 0)  //off_t len
         if (errno != EOPNOTSUPP) //possible, unlike with posix_fallocate()
@@ -308,19 +313,19 @@ void FileOutput::reserveSpace(uint64_t expectedSize) //throw FileError
 }
 
 
-std::string zen::getFileContent(const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
+std::string zen::getFileContent(const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
 {
     FileInput streamIn(filePath, notifyUnbufferedIO); //throw FileError, ErrorFileLocked
     return bufferedLoad<std::string>(streamIn); //throw FileError, X
 }
 
 
-void zen::setFileContent(const Zstring& filePath, const std::string& byteStream, const IOCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
+void zen::setFileContent(const Zstring& filePath, const std::string& byteStream, const IoCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
 {
     TempFileOutput fileOut(filePath, notifyUnbufferedIO); //throw FileError
     if (!byteStream.empty())
     {
-        //preallocate disk space + reduce fragmentation
+        //preallocate disk space & reduce fragmentation
         fileOut.reserveSpace(byteStream.size()); //throw FileError
         fileOut.write(&byteStream[0], byteStream.size()); //throw FileError, X
     }
diff --git a/zen/file_io.h b/zen/file_io.h
index a7385241..3d1dfee7 100644
--- a/zen/file_io.h
+++ b/zen/file_io.h
@@ -32,8 +32,7 @@ public:
     FileHandle getHandle() { return hFile_; }
 
     //Windows: use 64kB ?? https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-2000-server/cc938632%28v=technet.10%29
-    //Linux: use st_blksize?
-    //macOS: use f_iosize?
+    //macOS, Linux: use st_blksize?
     static size_t getBlockSize() { return 128 * 1024; };
 
     const Zstring& getFilePath() const { return filePath_; }
@@ -57,15 +56,15 @@ private:
 class FileInput : public FileBase
 {
 public:
-    FileInput(                   const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, ErrorFileLocked
-    FileInput(FileHandle handle, const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/); //takes ownership!
+    FileInput(                   const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, ErrorFileLocked
+    FileInput(FileHandle handle, const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/); //takes ownership!
 
     size_t read(void* buffer, size_t bytesToRead); //throw FileError, ErrorFileLocked, X; return "bytesToRead" bytes unless end of stream!
 
 private:
     size_t tryRead(void* buffer, size_t bytesToRead); //throw FileError, ErrorFileLocked; may return short, only 0 means EOF! =>  CONTRACT: bytesToRead > 0!
 
-    const IOCallback notifyUnbufferedIO_; //throw X
+    const IoCallback notifyUnbufferedIO_; //throw X
 
     std::vector<std::byte> memBuf_ = std::vector<std::byte>(getBlockSize());
     size_t bufPos_   = 0;
@@ -76,8 +75,8 @@ private:
 class FileOutput : public FileBase
 {
 public:
-    FileOutput(                   const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, ErrorTargetExisting
-    FileOutput(FileHandle handle, const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/); //takes ownership!
+    FileOutput(                   const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, ErrorTargetExisting
+    FileOutput(FileHandle handle, const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/); //takes ownership!
     ~FileOutput();
 
     void reserveSpace(uint64_t expectedSize); //throw FileError
@@ -91,7 +90,7 @@ public:
 private:
     size_t tryWrite(const void* buffer, size_t bytesToWrite); //throw FileError; may return short! CONTRACT: bytesToWrite > 0
 
-    IOCallback notifyUnbufferedIO_; //throw X
+    IoCallback notifyUnbufferedIO_; //throw X
     std::vector<std::byte> memBuf_ = std::vector<std::byte>(getBlockSize());
     size_t bufPos_    = 0;
     size_t bufPosEnd_ = 0;
@@ -102,7 +101,7 @@ private:
 class TempFileOutput
 {
 public:
-    TempFileOutput( const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/) : //throw FileError
+    TempFileOutput( const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/) : //throw FileError
         filePath_(filePath),
         tmpFile_(tmpFilePath_, notifyUnbufferedIO) {} //throw FileError, (ErrorTargetExisting)
 
@@ -110,7 +109,7 @@ public:
 
     void write(const void* buffer, size_t bytesToWrite) { tmpFile_.write(buffer, bytesToWrite); } //throw FileError, X
 
-     FileOutput& refTempFile() { return tmpFile_; }
+    FileOutput& refTempFile() { return tmpFile_; }
 
     void commit() //throw FileError, X
     {
@@ -133,10 +132,10 @@ private:
 };
 
 
-[[nodiscard]] std::string getFileContent(const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, X
+[[nodiscard]] std::string getFileContent(const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, X
 
 //overwrites if existing + transactional! :)
-void setFileContent(const Zstring& filePath, const std::string& bytes, const IOCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, X
+void setFileContent(const Zstring& filePath, const std::string& bytes, const IoCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, X
 }
 
 #endif //FILE_IO_H_89578342758342572345
diff --git a/zen/file_traverser.cpp b/zen/file_traverser.cpp
index aa48cb85..f1b5519b 100644
--- a/zen/file_traverser.cpp
+++ b/zen/file_traverser.cpp
@@ -31,7 +31,7 @@ void zen::traverseFolder(const Zstring& dirPath,
         for (;;)
         {
             errno = 0;
-            const struct ::dirent* dirEntry = ::readdir(folder); //don't use readdir_r(), see comment in native.cpp
+            const dirent* dirEntry = ::readdir(folder); //don't use readdir_r(), see comment in native.cpp
             if (!dirEntry)
             {
                 if (errno == 0) //errno left unchanged => no more items
@@ -54,7 +54,7 @@ void zen::traverseFolder(const Zstring& dirPath,
 
             const Zstring& itemPath = appendSeparator(dirPath) + itemName;
 
-            struct ::stat statData = {};
+            struct stat statData = {};
             try
             {
                 if (::lstat(itemPath.c_str(), &statData) != 0) //lstat() does not resolve symlinks
@@ -75,12 +75,12 @@ void zen::traverseFolder(const Zstring& dirPath,
             else if (S_ISDIR(statData.st_mode)) //a directory
             {
                 if (onFolder)
-                    onFolder({ itemName, itemPath });
+                    onFolder({itemName, itemPath});
             }
             else //a file or named pipe, etc.
             {
                 if (onFile)
-                    onFile({ itemName, itemPath, makeUnsigned(statData.st_size), statData.st_mtime });
+                    onFile({itemName, itemPath, makeUnsigned(statData.st_size), statData.st_mtime});
             }
 
             /* It may be a good idea to not check "S_ISREG(statData.st_mode)" explicitly and to not issue an error message on other types to support these scenarios:
diff --git a/zen/format_unit.cpp b/zen/format_unit.cpp
index 28943de7..b2d1b59a 100644
--- a/zen/format_unit.cpp
+++ b/zen/format_unit.cpp
@@ -128,9 +128,9 @@ std::wstring roundToBlock(double timeInHigh,
 
 std::wstring zen::formatRemainingTime(double timeInSec)
 {
-    const int steps10[] = { 1, 2, 5, 10 };
-    const int steps24[] = { 1, 2, 3, 4, 6, 8, 12, 24 };
-    const int steps60[] = { 1, 2, 5, 10, 15, 20, 30, 60 };
+    const int steps10[] = {1, 2, 5, 10};
+    const int steps24[] = {1, 2, 3, 4, 6, 8, 12, 24};
+    const int steps60[] = {1, 2, 5, 10, 15, 20, 30, 60};
 
     //determine preferred unit
     double timeInUnit = timeInSec;
@@ -178,7 +178,7 @@ std::wstring zen::formatUtcToLocalTime(time_t utcTime)
 {
     auto errorMsg = [&] { return _("Error") + L" (time_t: " + numberTo<std::wstring>(utcTime) + L')'; };
 
-    TimeComp loc = getLocalTime(utcTime);
+    const TimeComp& loc = getLocalTime(utcTime);
 
     std::wstring dateString = utfTo<std::wstring>(formatTime(Zstr("%x  %X"), loc));
     return !dateString.empty() ? dateString : errorMsg();
diff --git a/zen/http.cpp b/zen/http.cpp
index 5d389719..f8fb24a3 100644
--- a/zen/http.cpp
+++ b/zen/http.cpp
@@ -23,7 +23,7 @@ public:
          bool disableGetCache /*not relevant for POST (= never cached)*/,
          const Zstring& userAgent,
          const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-         const IOCallback& notifyUnbufferedIO) : //throw SysError, X
+         const IoCallback& notifyUnbufferedIO) : //throw SysError, X
         notifyUnbufferedIO_(notifyUnbufferedIO)
     {
         ZEN_ON_SCOPE_FAIL(cleanup(); /*destructor call would lead to member double clean-up!!!*/);
@@ -214,7 +214,7 @@ private:
 
     int64_t contentRemaining_ = -1; //consider "Content-Length" if available
 
-    const IOCallback notifyUnbufferedIO_; //throw X
+    const IoCallback notifyUnbufferedIO_; //throw X
 
     std::vector<std::byte> memBuf_ = std::vector<std::byte>(getBlockSize());
     size_t bufPos_    = 0; //buffered I/O; see file_io.cpp
@@ -240,7 +240,7 @@ std::unique_ptr<HttpInputStream::Impl> sendHttpRequestImpl(const Zstring& url,
                                                            const std::string& contentType, //required for POST
                                                            const Zstring& userAgent,
                                                            const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-                                                           const IOCallback& notifyUnbufferedIO) //throw SysError, X
+                                                           const IoCallback& notifyUnbufferedIO) //throw SysError, X
 {
     Zstring urlRed = url;
     //"A user agent should not automatically redirect a request more than five times, since such redirections usually indicate an infinite loop."
@@ -339,14 +339,14 @@ std::vector<std::pair<std::string, std::string>> zen::xWwwFormUrlDecode(const st
 }
 
 
-HttpInputStream zen::sendHttpGet(const Zstring& url, const Zstring& userAgent, const Zstring* caCertFilePath, const IOCallback& notifyUnbufferedIO) //throw SysError, X
+HttpInputStream zen::sendHttpGet(const Zstring& url, const Zstring& userAgent, const Zstring* caCertFilePath, const IoCallback& notifyUnbufferedIO) //throw SysError, X
 {
     return sendHttpRequestImpl(url, nullptr /*postBuf*/, "" /*contentType*/, userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError, X, X
 }
 
 
 HttpInputStream zen::sendHttpPost(const Zstring& url, const std::vector<std::pair<std::string, std::string>>& postParams,
-                                  const Zstring& userAgent, const Zstring* caCertFilePath, const IOCallback& notifyUnbufferedIO) //throw SysError, X
+                                  const Zstring& userAgent, const Zstring* caCertFilePath, const IoCallback& notifyUnbufferedIO) //throw SysError, X
 {
     return sendHttpPost(url, xWwwFormUrlEncode(postParams), "application/x-www-form-urlencoded", userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError, X
 }
@@ -354,7 +354,7 @@ HttpInputStream zen::sendHttpPost(const Zstring& url, const std::vector<std::pai
 
 
 HttpInputStream zen::sendHttpPost(const Zstring& url, const std::string& postBuf, const std::string& contentType,
-                                  const Zstring& userAgent, const Zstring* caCertFilePath, const IOCallback& notifyUnbufferedIO) //throw SysError, X
+                                  const Zstring& userAgent, const Zstring* caCertFilePath, const IoCallback& notifyUnbufferedIO) //throw SysError, X
 {
     return sendHttpRequestImpl(url, &postBuf, contentType, userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError, X
 }
diff --git a/zen/http.h b/zen/http.h
index 6cb107bf..07c3f28c 100644
--- a/zen/http.h
+++ b/zen/http.h
@@ -39,19 +39,19 @@ private:
 HttpInputStream sendHttpGet(const Zstring& url,
                             const Zstring& userAgent,
                             const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-                            const IOCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
+                            const IoCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
 
 HttpInputStream sendHttpPost(const Zstring& url,
                              const std::vector<std::pair<std::string, std::string>>& postParams,
                              const Zstring& userAgent,
                              const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-                             const IOCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
+                             const IoCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
 
 HttpInputStream sendHttpPost(const Zstring& url,
                              const std::string& postBuf, const std::string& contentType,
                              const Zstring& userAgent,
                              const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-                             const IOCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
+                             const IoCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
 
 bool internetIsAlive(); //noexcept
 std::wstring formatHttpError(int httpStatus);
diff --git a/zen/json.h b/zen/json.h
index a3740664..f6458d6a 100644
--- a/zen/json.h
+++ b/zen/json.h
@@ -372,7 +372,7 @@ public:
                 if (*it == '"')
                 {
                     Token tk(Token::Type::string);
-                    tk.primVal = jsonUnescape({ pos_, it });
+                    tk.primVal = jsonUnescape({pos_, it});
                     pos_ = ++it;
                     return tk;
                 }
diff --git a/zen/open_ssl.cpp b/zen/open_ssl.cpp
index ea77db43..7c94263a 100644
--- a/zen/open_ssl.cpp
+++ b/zen/open_ssl.cpp
@@ -79,7 +79,7 @@ std::wstring formatLastOpenSSLError(const char* functionName)
 
 std::shared_ptr<EVP_PKEY> generateRsaKeyPair(int bits) //throw SysError
 {
-    EVP_PKEY_CTX* keyCtx = ::EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, //int id,
+    EVP_PKEY_CTX* keyCtx = ::EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, //int id
                                                  nullptr);     //ENGINE* e
     if (!keyCtx)
         throw SysError(formatLastOpenSSLError("EVP_PKEY_CTX_new_id"));
@@ -110,9 +110,9 @@ std::shared_ptr<EVP_PKEY> streamToEvpKey(const std::string& keyStream, BioToEvpF
         throw SysError(formatLastOpenSSLError("BIO_new_mem_buf"));
     ZEN_ON_SCOPE_EXIT(::BIO_free_all(bio));
 
-    if (EVP_PKEY* evp = bioToEvp(bio,      //BIO* bp,
-                                 nullptr,  //EVP_PKEY** x,
-                                 nullptr,  //pem_password_cb* cb,
+    if (EVP_PKEY* evp = bioToEvp(bio,      //BIO* bp
+                                 nullptr,  //EVP_PKEY** x
+                                 nullptr,  //pem_password_cb* cb
                                  nullptr)) //void* u
         return std::shared_ptr<EVP_PKEY>(evp, ::EVP_PKEY_free);
     throw SysError(formatLastOpenSSLError(functionName));
@@ -128,9 +128,9 @@ std::shared_ptr<EVP_PKEY> streamToEvpKey(const std::string& keyStream, BioToRsaF
         throw SysError(formatLastOpenSSLError("BIO_new_mem_buf"));
     ZEN_ON_SCOPE_EXIT(::BIO_free_all(bio));
 
-    RSA* rsa = bioToRsa(bio,      //BIO* bp,
-                        nullptr,  //RSA** x,
-                        nullptr,  //pem_password_cb* cb,
+    RSA* rsa = bioToRsa(bio,      //BIO* bp
+                        nullptr,  //RSA** x
+                        nullptr,  //pem_password_cb* cb
                         nullptr); //void* u
     if (!rsa)
         throw SysError(formatLastOpenSSLError(functionName));
@@ -168,9 +168,9 @@ std::shared_ptr<EVP_PKEY> streamToKey(const std::string& keyStream, RsaStreamTyp
     }
 
     auto tmp = reinterpret_cast<const unsigned char*>(keyStream.c_str());
-    EVP_PKEY* evp = (publicKey ? ::d2i_PublicKey : ::d2i_PrivateKey)(EVP_PKEY_RSA,                         //int type,
-                                                                     nullptr,                              //EVP_PKEY** a,
-                                                                     &tmp, /*changes tmp pointer itself!*/ //const unsigned char** pp,
+    EVP_PKEY* evp = (publicKey ? ::d2i_PublicKey : ::d2i_PrivateKey)(EVP_PKEY_RSA,                         //int type
+                                                                     nullptr,                              //EVP_PKEY** a
+                                                                     &tmp, /*changes tmp pointer itself!*/ //const unsigned char** pp
                                                                      static_cast<long>(keyStream.size())); //long length
     if (!evp)
         throw SysError(formatLastOpenSSLError(publicKey ? "d2i_PublicKey" : "d2i_PrivateKey"));
@@ -238,23 +238,23 @@ std::string evpKeyToStream(EVP_PKEY* evp, RsaToBioFunc rsaToBio, const char* fun
 //fix OpenSSL API inconsistencies:
 int PEM_write_bio_PrivateKey2(BIO* bio, EVP_PKEY* key)
 {
-    return ::PEM_write_bio_PrivateKey(bio,      //BIO* bp,
-                                      key,      //EVP_PKEY* x,
-                                      nullptr,  //const EVP_CIPHER* enc,
-                                      nullptr,  //unsigned char* kstr,
-                                      0,        //int klen,
-                                      nullptr,  //pem_password_cb* cb,
+    return ::PEM_write_bio_PrivateKey(bio,      //BIO* bp
+                                      key,      //EVP_PKEY* x
+                                      nullptr,  //const EVP_CIPHER* enc
+                                      nullptr,  //unsigned char* kstr
+                                      0,        //int klen
+                                      nullptr,  //pem_password_cb* cb
                                       nullptr); //void* u
 }
 
 int PEM_write_bio_RSAPrivateKey2(BIO* bio, RSA* rsa)
 {
-    return ::PEM_write_bio_RSAPrivateKey(bio,      //BIO* bp,
-                                         rsa,      //RSA* x,
-                                         nullptr,  //const EVP_CIPHER* enc,
-                                         nullptr,  //unsigned char* kstr,
-                                         0,        //int klen,
-                                         nullptr,  //pem_password_cb* cb,
+    return ::PEM_write_bio_RSAPrivateKey(bio,      //BIO* bp
+                                         rsa,      //RSA* x
+                                         nullptr,  //const EVP_CIPHER* enc
+                                         nullptr,  //unsigned char* kstr
+                                         0,        //int klen
+                                         nullptr,  //pem_password_cb* cb
                                          nullptr); //void* u
 }
 
@@ -286,7 +286,7 @@ std::string keyToStream(EVP_PKEY* evp, RsaStreamType streamType, bool publicKey)
         throw SysError(formatLastOpenSSLError(publicKey ? "i2d_PublicKey" : "i2d_PrivateKey"));
     ZEN_ON_SCOPE_EXIT(::OPENSSL_free(buf)); //memory is only allocated for bufSize > 0
 
-    return { reinterpret_cast<const char*>(buf), static_cast<size_t>(bufSize) };
+    return {reinterpret_cast<const char*>(buf), static_cast<size_t>(bufSize)};
 }
 
 //================================================================================
@@ -299,29 +299,29 @@ std::string createSignature(const std::string& message, EVP_PKEY* privateKey) //
         throw SysError(formatSystemError("EVP_MD_CTX_create", L"", L"Unexpected failure.")); //no more error details
     ZEN_ON_SCOPE_EXIT(::EVP_MD_CTX_destroy(mdctx));
 
-    if (::EVP_DigestSignInit(mdctx,            //EVP_MD_CTX* ctx,
-                             nullptr,          //EVP_PKEY_CTX** pctx,
-                             EVP_sha256(),     //const EVP_MD* type,
-                             nullptr,          //ENGINE* e,
+    if (::EVP_DigestSignInit(mdctx,            //EVP_MD_CTX* ctx
+                             nullptr,          //EVP_PKEY_CTX** pctx
+                             EVP_sha256(),     //const EVP_MD* type
+                             nullptr,          //ENGINE* e
                              privateKey) != 1) //EVP_PKEY* pkey
         throw SysError(formatLastOpenSSLError("EVP_DigestSignInit"));
 
-    if (::EVP_DigestSignUpdate(mdctx,                //EVP_MD_CTX* ctx,
-                               message.c_str(),      //const void* d,
+    if (::EVP_DigestSignUpdate(mdctx,                //EVP_MD_CTX* ctx
+                               message.c_str(),      //const void* d
                                message.size()) != 1) //size_t cnt
         throw SysError(formatLastOpenSSLError("EVP_DigestSignUpdate"));
 
     size_t sigLenMax = 0; //"first call to EVP_DigestSignFinal returns the maximum buffer size required"
-    if (::EVP_DigestSignFinal(mdctx,            //EVP_MD_CTX* ctx,
-                              nullptr,          //unsigned char* sigret,
+    if (::EVP_DigestSignFinal(mdctx,            //EVP_MD_CTX* ctx
+                              nullptr,          //unsigned char* sigret
                               &sigLenMax) != 1) //size_t* siglen
         throw SysError(formatLastOpenSSLError("EVP_DigestSignFinal"));
 
     std::string signature(sigLenMax, '\0');
     size_t sigLen = sigLenMax;
 
-    if (::EVP_DigestSignFinal(mdctx,                                           //EVP_MD_CTX* ctx,
-                              reinterpret_cast<unsigned char*>(&signature[0]), //unsigned char* sigret,
+    if (::EVP_DigestSignFinal(mdctx,                                           //EVP_MD_CTX* ctx
+                              reinterpret_cast<unsigned char*>(&signature[0]), //unsigned char* sigret
                               &sigLen) != 1)                                   //size_t* siglen
         throw SysError(formatLastOpenSSLError("EVP_DigestSignFinal"));
 
@@ -338,20 +338,20 @@ void verifySignature(const std::string& message, const std::string& signature, E
         throw SysError(formatSystemError("EVP_MD_CTX_create", L"", L"Unexpected failure.")); //no more error details
     ZEN_ON_SCOPE_EXIT(::EVP_MD_CTX_destroy(mdctx));
 
-    if (::EVP_DigestVerifyInit(mdctx,           //EVP_MD_CTX* ctx,
-                               nullptr,         //EVP_PKEY_CTX** pctx,
-                               EVP_sha256(),    //const EVP_MD* type,
-                               nullptr,         //ENGINE* e,
+    if (::EVP_DigestVerifyInit(mdctx,           //EVP_MD_CTX* ctx
+                               nullptr,         //EVP_PKEY_CTX** pctx
+                               EVP_sha256(),    //const EVP_MD* type
+                               nullptr,         //ENGINE* e
                                publicKey) != 1) //EVP_PKEY* pkey
         throw SysError(formatLastOpenSSLError("EVP_DigestVerifyInit"));
 
-    if (::EVP_DigestVerifyUpdate(mdctx,                //EVP_MD_CTX* ctx,
-                                 message.c_str(),      //const void* d,
+    if (::EVP_DigestVerifyUpdate(mdctx,                //EVP_MD_CTX* ctx
+                                 message.c_str(),      //const void* d
                                  message.size()) != 1) //size_t cnt
         throw SysError(formatLastOpenSSLError("EVP_DigestVerifyUpdate"));
 
-    if (::EVP_DigestVerifyFinal(mdctx,                                                     //EVP_MD_CTX* ctx,
-                                reinterpret_cast<const unsigned char*>(signature.c_str()), //const unsigned char* sig,
+    if (::EVP_DigestVerifyFinal(mdctx,                                                     //EVP_MD_CTX* ctx
+                                reinterpret_cast<const unsigned char*>(signature.c_str()), //const unsigned char* sig
                                 signature.size()) != 1)                                    //size_t siglen
         throw SysError(formatLastOpenSSLError("EVP_DigestVerifyFinal"));
 }
@@ -735,10 +735,10 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
             throw SysError(formatSystemError("EVP_CIPHER_CTX_new", L"", L"Unexpected failure.")); //no more error details
         ZEN_ON_SCOPE_EXIT(::EVP_CIPHER_CTX_free(cipCtx));
 
-        if (::EVP_DecryptInit_ex(cipCtx,            //EVP_CIPHER_CTX* ctx,
-                                 EVP_aes_256_cbc(), //const EVP_CIPHER* type,
-                                 nullptr,           //ENGINE* impl,
-                                 key,               //const unsigned char* key, => implied length of 256 bit!
+        if (::EVP_DecryptInit_ex(cipCtx,            //EVP_CIPHER_CTX* ctx
+                                 EVP_aes_256_cbc(), //const EVP_CIPHER* type
+                                 nullptr,           //ENGINE* impl
+                                 key,               //const unsigned char* key => implied length of 256 bit!
                                  nullptr) != 1)     //const unsigned char* iv
             throw SysError(formatLastOpenSSLError("EVP_DecryptInit_ex"));
 
@@ -749,16 +749,16 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
         //"EVP_DecryptUpdate() should have room for (inl + cipher_block_size) bytes"
 
         int decLen1 = 0;
-        if (::EVP_DecryptUpdate(cipCtx,                                                         //EVP_CIPHER_CTX* ctx,
-                                reinterpret_cast<unsigned char*>(&privateBlob[0]),              //unsigned char* out,
-                                &decLen1,                                                       //int* outl,
-                                reinterpret_cast<const unsigned char*>(privateBlobEnc.c_str()), //const unsigned char* in,
+        if (::EVP_DecryptUpdate(cipCtx,                                                         //EVP_CIPHER_CTX* ctx
+                                reinterpret_cast<unsigned char*>(&privateBlob[0]),              //unsigned char* out
+                                &decLen1,                                                       //int* outl
+                                reinterpret_cast<const unsigned char*>(privateBlobEnc.c_str()), //const unsigned char* in
                                 static_cast<int>(privateBlobEnc.size())) != 1)                  //int inl
             throw SysError(formatLastOpenSSLError("EVP_DecryptUpdate"));
 
         int decLen2 = 0;
-        if (::EVP_DecryptFinal_ex(cipCtx,                                                  //EVP_CIPHER_CTX* ctx,
-                                  reinterpret_cast<unsigned char*>(&privateBlob[decLen1]), //unsigned char* outm,
+        if (::EVP_DecryptFinal_ex(cipCtx,                                                  //EVP_CIPHER_CTX* ctx
+                                  reinterpret_cast<unsigned char*>(&privateBlob[decLen1]), //unsigned char* outm
                                   &decLen2) != 1)                                          //int* outl
             throw SysError(formatLastOpenSSLError("EVP_DecryptFinal_ex"));
 
@@ -777,7 +777,7 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
     {
         static_assert(std::endian::native == std::endian::little&& sizeof(n) >= 4);
         const char* numStr = reinterpret_cast<const char*>(&n);
-        return { numStr[3], numStr[2], numStr[1], numStr[0] }; //big endian!
+        return {numStr[3], numStr[2], numStr[1], numStr[0]}; //big endian!
     };
 
     const std::string macData = numToBeString(algorithm    .size()) + algorithm +
@@ -787,13 +787,13 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
                                 numToBeString(privateBlob  .size()) + privateBlob;
     char md[EVP_MAX_MD_SIZE] = {};
     unsigned int mdLen = 0;
-    if (!::HMAC(EVP_sha1(),      //const EVP_MD* evp_md,
-                macKey,          //const void* key,
-                sizeof(macKey),  //int key_len,
-                reinterpret_cast<const unsigned char*>(macData.c_str()), //const unsigned char* d,
-                static_cast<int>(macData.size()),     //int n,
-                reinterpret_cast<unsigned char*>(md), //unsigned char* md,
-                &mdLen))         //unsigned int* md_len
+    if (!::HMAC(EVP_sha1(),                           //const EVP_MD* evp_md
+                macKey,                               //const void* key
+                sizeof(macKey),                       //int key_len
+                reinterpret_cast<const unsigned char*>(macData.c_str()), //const unsigned char* d
+                static_cast<int>(macData.size()),     //int n
+                reinterpret_cast<unsigned char*>(md), //unsigned char* md
+                &mdLen))                              //unsigned int* md_len
         throw SysError(formatSystemError("HMAC", L"", L"Unexpected failure.")); //no more error details
 
     const bool hashValid = mac == std::string_view(md, mdLen);
@@ -979,10 +979,10 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
             throw SysError(formatLastOpenSSLError("EC_POINT_new"));
         ZEN_ON_SCOPE_EXIT(::EC_POINT_free(ecPoint));
 
-        if (::EC_POINT_oct2point(ecGroup,            //const EC_GROUP* group,
-                                 ecPoint,            //EC_POINT* p,
-                                 reinterpret_cast<const unsigned char*>(&pointStream[0]), //const unsigned char* buf,
-                                 pointStream.size(), //size_t len,
+        if (::EC_POINT_oct2point(ecGroup,            //const EC_GROUP* group
+                                 ecPoint,            //EC_POINT* p
+                                 reinterpret_cast<const unsigned char*>(&pointStream[0]), //const unsigned char* buf
+                                 pointStream.size(), //size_t len
                                  nullptr) != 1)      //BN_CTX* ctx
             throw SysError(formatLastOpenSSLError("EC_POINT_oct2point"));
 
@@ -1008,9 +1008,9 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
         //const std::string pubStream = extractStringPub(); -> we don't need the public key
         const std::string priStream = extractStringPriv();
 
-        EVP_PKEY* evpPriv = ::EVP_PKEY_new_raw_private_key(EVP_PKEY_ED25519,  //int type,
-                                                           nullptr,           //ENGINE* e,
-                                                           reinterpret_cast<const unsigned char*>(&priStream[0]), //const unsigned char* priv,
+        EVP_PKEY* evpPriv = ::EVP_PKEY_new_raw_private_key(EVP_PKEY_ED25519,  //int type
+                                                           nullptr,           //ENGINE* e
+                                                           reinterpret_cast<const unsigned char*>(&priStream[0]), //const unsigned char* priv
                                                            priStream.size()); //size_t len
         if (!evpPriv)
             throw SysError(formatLastOpenSSLError("EVP_PKEY_new_raw_private_key"));
diff --git a/zen/perf.h b/zen/perf.h
index 6bc328bb..2ebf1955 100644
--- a/zen/perf.h
+++ b/zen/perf.h
@@ -23,21 +23,20 @@
 
     static zen::PerfTimer perfTest(true); //startPaused
     perfTest.resume();
-    ZEN_ON_SCOPE_EXIT(perfTest.pause());
-*/
+    ZEN_ON_SCOPE_EXIT(perfTest.pause());                      */
 
 namespace zen
 {
-//issue with wxStopWatch? https://freefilesync.org/forum/viewtopic.php?t=1426
-// => wxStopWatch implementation uses QueryPerformanceCounter: https://github.com/wxWidgets/wxWidgets/blob/17d72a48ffd4d8ff42eed070ac48ee2de50ceabd/src/common/stopwatch.cpp
-// => whatever the problem was, it's almost certainly not caused by QueryPerformanceCounter():
-//      MSDN: "How often does QPC roll over? Not less than 100 years from the most recent system boot"
-//      https://docs.microsoft.com/en-us/windows/win32/sysinfo/acquiring-high-resolution-time-stamps#general-faq-about-qpc-and-tsc
-//
-// => using the system clock is problematic: https://freefilesync.org/forum/viewtopic.php?t=5280
-//
-//    std::chrono::system_clock wraps ::GetSystemTimePreciseAsFileTime()
-//    std::chrono::steady_clock wraps ::QueryPerformanceCounter()
+/* issue with wxStopWatch? https://freefilesync.org/forum/viewtopic.php?t=1426
+     - wxStopWatch implementation uses QueryPerformanceCounter: https://github.com/wxWidgets/wxWidgets/blob/17d72a48ffd4d8ff42eed070ac48ee2de50ceabd/src/common/stopwatch.cpp
+     - whatever the problem was, it's almost certainly not caused by QueryPerformanceCounter():
+          MSDN: "How often does QPC roll over? Not less than 100 years from the most recent system boot"
+          https://docs.microsoft.com/en-us/windows/win32/sysinfo/acquiring-high-resolution-time-stamps#general-faq-about-qpc-and-tsc
+
+     - using the system clock is problematic: https://freefilesync.org/forum/viewtopic.php?t=5280
+
+       std::chrono::system_clock wraps ::GetSystemTimePreciseAsFileTime()
+       std::chrono::steady_clock wraps ::QueryPerformanceCounter()                       */
 class StopWatch
 {
 public:
diff --git a/zen/process_exec.cpp b/zen/process_exec.cpp
index bbc87c51..b82c2565 100644
--- a/zen/process_exec.cpp
+++ b/zen/process_exec.cpp
@@ -117,7 +117,7 @@ std::pair<int /*exit code*/, std::string> processExecuteImpl(const Zstring& file
             if (::dup(fdLifeSignW) == -1) //O_CLOEXEC does NOT propagate with dup()
                 THROW_LAST_SYS_ERROR("dup(fdLifeSignW)");
 
-            std::vector<const char*> argv{ filePath.c_str() };
+            std::vector<const char*> argv{filePath.c_str()};
             for (const Zstring& arg : arguments)
                 argv.push_back(arg.c_str());
             argv.push_back(nullptr);
@@ -147,6 +147,8 @@ std::pair<int /*exit code*/, std::string> processExecuteImpl(const Zstring& file
         if (flags == -1)
             THROW_LAST_SYS_ERROR("fcntl(F_GETFL)");
 
+        //fcntl() success: Linux: 0
+        //                 macOS: "Value other than -1."
         if (::fcntl(fdLifeSignR, F_SETFL, flags | O_NONBLOCK) == -1)
             THROW_LAST_SYS_ERROR("fcntl(F_SETFL, O_NONBLOCK)");
 
@@ -174,7 +176,7 @@ std::pair<int /*exit code*/, std::string> processExecuteImpl(const Zstring& file
 
             const auto waitTimeMs = std::chrono::duration_cast<std::chrono::milliseconds>(endTime - now).count();
 
-            struct ::timeval tv = {};
+            timeval tv = {};
             tv.tv_sec  = static_cast<long>(waitTimeMs / 1000);
             tv.tv_usec = static_cast<long>(waitTimeMs - tv.tv_sec * 1000) * 1000;
 
@@ -219,7 +221,7 @@ std::pair<int /*exit code*/, std::string> processExecuteImpl(const Zstring& file
         exitCode == 127) //details should have been streamed to STDERR: used by /bin/sh, e.g. failure to execute due to missing .so file
         throw SysError(utfTo<std::wstring>(trimCpy(output)));
 
-    return { exitCode, output };
+    return {exitCode, output};
 }
 }
 
diff --git a/zen/resolve_path.cpp b/zen/resolve_path.cpp
index 76999500..0e714528 100644
--- a/zen/resolve_path.cpp
+++ b/zen/resolve_path.cpp
@@ -5,17 +5,12 @@
 // *****************************************************************************
 
 #include "resolve_path.h"
-//#include <set> //not necessarily included by <map>!
-//#include <map>
 #include "time.h"
 #include "thread.h"
-//#include "utf.h"
-//#include "scope_guard.h"
-//#include "globals.h"
 #include "file_access.h"
 
     #include <stdlib.h> //getenv()
-    #include <unistd.h> //getcwd
+    #include <unistd.h> //getcwd()
 
 using namespace zen;
 
@@ -251,7 +246,7 @@ std::vector<Zstring> zen::getFolderPathAliases(const Zstring& folderPathPhrase)
     tmp.erase(dirPath);
     tmp.erase(Zstring());
 
-    return { tmp.begin(), tmp.end() };
+    return {tmp.begin(), tmp.end()};
 }
 
 
diff --git a/zen/ring_buffer.h b/zen/ring_buffer.h
index 240262fa..ae2377d8 100644
--- a/zen/ring_buffer.h
+++ b/zen/ring_buffer.h
@@ -196,11 +196,11 @@ public:
     using iterator        = Iterator<      RingBuffer,       T>;
     using const_iterator  = Iterator<const RingBuffer, const T>;
 
-    iterator begin() { return { *this, 0     }; }
-    iterator end  () { return { *this, size_ }; }
+    iterator begin() { return {*this, 0    }; }
+    iterator end  () { return {*this, size_}; }
 
-    const_iterator begin() const { return { *this, 0     }; }
-    const_iterator end  () const { return { *this, size_ }; }
+    const_iterator begin() const { return {*this, 0    }; }
+    const_iterator end  () const { return {*this, size_}; }
 
     const_iterator cbegin() const { return begin(); }
     const_iterator cend  () const { return end  (); }
diff --git a/zen/serialize.h b/zen/serialize.h
index 6c57e4ee..f9677630 100644
--- a/zen/serialize.h
+++ b/zen/serialize.h
@@ -35,7 +35,7 @@ struct BufferedInputStream
 Optional: support stream-copying
 --------------------------------
     size_t getBlockSize() const;
-    const IOCallback& notifyUnbufferedIO
+    const IoCallback& notifyUnbufferedIO
 };
 
 --------------------------------
@@ -47,9 +47,9 @@ struct BufferedOutputStream
 
 Optional: support stream-copying
 --------------------------------
-    const IOCallback& notifyUnbufferedIO
+    const IoCallback& notifyUnbufferedIO
 };                                                                           */
-using IOCallback = std::function<void(int64_t bytesDelta)>; //throw X
+using IoCallback = std::function<void(int64_t bytesDelta)>; //throw X
 
 
 //functions based on buffered stream abstraction
@@ -75,7 +75,7 @@ template <         class BufferedInputStream> void readArray    (BufferedInputSt
 
 struct IOCallbackDivider
 {
-    IOCallbackDivider(const IOCallback& notifyUnbufferedIO, int64_t& totalUnbufferedIO) : totalUnbufferedIO_(totalUnbufferedIO), notifyUnbufferedIO_(notifyUnbufferedIO) {}
+    IOCallbackDivider(const IoCallback& notifyUnbufferedIO, int64_t& totalUnbufferedIO) : totalUnbufferedIO_(totalUnbufferedIO), notifyUnbufferedIO_(notifyUnbufferedIO) {}
 
     void operator()(int64_t bytesDelta)
     {
@@ -85,7 +85,7 @@ struct IOCallbackDivider
 
 private:
     int64_t& totalUnbufferedIO_;
-    const IOCallback& notifyUnbufferedIO_;
+    const IoCallback& notifyUnbufferedIO_;
 };
 
 
@@ -206,7 +206,7 @@ void writeArray(BufferedOutputStream& stream, const void* buffer, size_t len)
 template <class N, class BufferedOutputStream> inline
 void writeNumber(BufferedOutputStream& stream, const N& num)
 {
-    static_assert(IsArithmetic<N>::value || std::is_same_v<N, bool> || std::is_enum_v<N>);
+    static_assert(IsArithmeticV<N> || std::is_same_v<N, bool> || std::is_enum_v<N>);
     writeArray(stream, &num, sizeof(N));
 }
 
@@ -234,7 +234,7 @@ void readArray(BufferedInputStream& stream, void* buffer, size_t len) //throw Sy
 template <class N, class BufferedInputStream> inline
 N readNumber(BufferedInputStream& stream) //throw SysErrorUnexpectedEos
 {
-    static_assert(IsArithmetic<N>::value || std::is_same_v<N, bool> || std::is_enum_v<N>);
+    static_assert(IsArithmeticV<N> || std::is_same_v<N, bool> || std::is_enum_v<N>);
     N num{};
     readArray(stream, &num, sizeof(N)); //throw SysErrorUnexpectedEos
     return num;
diff --git a/zen/stl_tools.h b/zen/stl_tools.h
index 495ff8d1..53b95241 100644
--- a/zen/stl_tools.h
+++ b/zen/stl_tools.h
@@ -128,7 +128,7 @@ void removeDuplicates(std::vector<T, Alloc>& v, CompLess less)
 template <class T, class Alloc> inline
 void removeDuplicates(std::vector<T, Alloc>& v)
 {
-    removeDuplicates(v, std::less<T>(), std::equal_to<T>());
+    removeDuplicates(v, std::less(), std::equal_to());
 }
 
 
@@ -233,6 +233,7 @@ class FNV1aHash
 {
 public:
     FNV1aHash() {}
+    explicit FNV1aHash(Num startVal) : hashVal_(startVal) {}
 
     void add(Num n)
     {
@@ -243,8 +244,8 @@ public:
     Num get() const { return hashVal_; }
 
 private:
-    static_assert(IsUnsignedInt<Num>::value);
-    static_assert(sizeof(Num) == 4 || sizeof(Num) == 8); //macOS: size_t is "unsigned long"
+    static_assert(IsUnsignedIntV<Num>);
+    static_assert(sizeof(Num) == 4 || sizeof(Num) == 8);
     static constexpr Num base_  = sizeof(Num) == 4 ? 2166136261U : 14695981039346656037ULL;
     static constexpr Num prime_ = sizeof(Num) == 4 ?   16777619U :        1099511628211ULL;
 
@@ -257,7 +258,7 @@ Num hashArray(ByteIterator first, ByteIterator last)
 {
     using ValType = typename std::iterator_traits<ByteIterator>::value_type;
     static_assert(sizeof(ValType) <= sizeof(Num));
-    static_assert(IsInteger<ValType>::value || std::is_same_v<ValType, char> || std::is_same_v<ValType, wchar_t>);
+    static_assert(IsIntegerV<ValType> || std::is_same_v<ValType, char> || std::is_same_v<ValType, wchar_t>);
 
     FNV1aHash<Num> hash;
     std::for_each(first, last, [&hash](ValType v) { hash.add(v); });
@@ -265,8 +266,7 @@ Num hashArray(ByteIterator first, ByteIterator last)
 }
 
 
-//support for custom string classes in std::unordered_set/map
-struct StringHash
+struct StringHash //support for custom string classes with std::unordered_set/map
 {
     template <class String>
     size_t operator()(const String& str) const
diff --git a/zen/string_tools.h b/zen/string_tools.h
index 883c45b8..8150df05 100644
--- a/zen/string_tools.h
+++ b/zen/string_tools.h
@@ -395,7 +395,7 @@ std::vector<S> split(const S& str, const T& delimiter, SplitOnEmpty soe)
     {
         if (str.empty() && soe == SplitOnEmpty::skip)
             return {};
-        return { str };
+        return {str};
     }
 
     const auto* const delimFirst = strBegin(delimiter);
@@ -800,9 +800,9 @@ template <class S, class Num> inline
 S numberTo(const Num& number)
 {
     using TypeTag = std::integral_constant<impl::NumberType,
-                                           IsSignedInt  <Num>::value ? impl::NumberType::signedInt :
-                                           IsUnsignedInt<Num>::value ? impl::NumberType::unsignedInt :
-                                           IsFloat      <Num>::value ? impl::NumberType::floatingPoint :
+                                           IsSignedIntV  <Num> ? impl::NumberType::signedInt :
+                                           IsUnsignedIntV<Num> ? impl::NumberType::unsignedInt :
+                                           IsFloatV      <Num> ? impl::NumberType::floatingPoint :
                                            impl::NumberType::other>;
 
     return impl::numberTo<S>(number, TypeTag());
@@ -813,9 +813,9 @@ template <class Num, class S> inline
 Num stringTo(const S& str)
 {
     using TypeTag = std::integral_constant<impl::NumberType,
-                                           IsSignedInt  <Num>::value ? impl::NumberType::signedInt :
-                                           IsUnsignedInt<Num>::value ? impl::NumberType::unsignedInt :
-                                           IsFloat      <Num>::value ? impl::NumberType::floatingPoint :
+                                           IsSignedIntV  <Num> ? impl::NumberType::signedInt :
+                                           IsUnsignedIntV<Num> ? impl::NumberType::unsignedInt :
+                                           IsFloatV      <Num> ? impl::NumberType::floatingPoint :
                                            impl::NumberType::other>;
 
     return impl::stringTo<Num>(str, TypeTag());
@@ -836,7 +836,7 @@ std::pair<char, char> hexify(unsigned char c, bool upperCase)
         else
             return static_cast<char>('a' + (num - 10));
     };
-    return { hexifyDigit(c / 16), hexifyDigit(c % 16) };
+    return {hexifyDigit(c / 16), hexifyDigit(c % 16)};
 }
 
 
diff --git a/zen/string_traits.h b/zen/string_traits.h
index d9ce589c..ca40f7d6 100644
--- a/zen/string_traits.h
+++ b/zen/string_traits.h
@@ -120,19 +120,12 @@ public:
 };
 }
 
-template <class T>
-struct IsStringLike : std::bool_constant<impl::StringTraits<T>::isStringLike> {};
 
-template <class T>
-struct GetCharType { using Type = typename impl::StringTraits<T>::CharType; };
-
-
-//template alias helpers:
 template<class T>
-constexpr bool IsStringLikeV = IsStringLike<T>::value;
+constexpr bool IsStringLikeV = impl::StringTraits<T>::isStringLike;
 
 template<class T>
-using GetCharTypeT = typename GetCharType<T>::Type;
+using GetCharTypeT = typename impl::StringTraits<T>::CharType;
 
 
 namespace impl
diff --git a/zen/symlink_target.h b/zen/symlink_target.h
index 42010fd2..32b1211d 100644
--- a/zen/symlink_target.h
+++ b/zen/symlink_target.h
@@ -70,11 +70,11 @@ Zstring getResolvedSymlinkPath_impl(const Zstring& linkPath) //throw FileError
 namespace zen
 {
 inline
-SymlinkRawContent getSymlinkRawContent(const Zstring& linkPath) { return getSymlinkRawContent_impl(linkPath); }
+SymlinkRawContent getSymlinkRawContent(const Zstring& linkPath) { return getSymlinkRawContent_impl(linkPath); } //throw FileError
 
 
 inline
-Zstring getSymlinkResolvedPath(const Zstring& linkPath) { return getResolvedSymlinkPath_impl(linkPath); }
+Zstring getSymlinkResolvedPath(const Zstring& linkPath) { return getResolvedSymlinkPath_impl(linkPath); } //throw FileError
 
 }
 
diff --git a/zen/sys_info.cpp b/zen/sys_info.cpp
index f6045f7e..1a0d18f5 100644
--- a/zen/sys_info.cpp
+++ b/zen/sys_info.cpp
@@ -25,17 +25,14 @@ using namespace zen;
 
 std::wstring zen::getUserName() //throw FileError
 {
-    const uid_t userIdNo = ::getuid(); //"real user ID"; never fails
-
-    std::vector<char> buffer(std::max<long>(10000, ::sysconf(_SC_GETPW_R_SIZE_MAX))); //::sysconf may return long(-1)
-    struct passwd buffer2 = {};
-    struct passwd* pwsEntry = nullptr;
-    if (::getpwuid_r(userIdNo, &buffer2, &buffer[0], buffer.size(), &pwsEntry) != 0) //getlogin() is deprecated and not working on Ubuntu at all!!!
-        THROW_LAST_FILE_ERROR(_("Cannot get process information."), "getpwuid_r");
-    if (!pwsEntry)
-        throw FileError(_("Cannot get process information."), L"no login found"); //should not happen?
-
-    return utfTo<std::wstring>(pwsEntry->pw_name);
+    //https://linux.die.net/man/3/getlogin
+    //https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/getlogin.2.html
+    const char* loginUser = ::getlogin();
+    if (!loginUser)
+        THROW_LAST_FILE_ERROR(_("Cannot get process information."), "getlogin");
+    //getlogin() is smarter than simply evaluating $LOGNAME! even in contexts without
+    //$LOGNAME, e.g. "sudo su" on Ubuntu, it returns the correct non-root user!
+    return utfTo<std::wstring>(loginUser);
 }
 
 
@@ -64,7 +61,7 @@ ComputerModel zen::getComputerModel() //throw FileError
         cm.vendor = tryGetInfo("/sys/devices/virtual/dmi/id/sys_vendor");   //
 
         //clean up:
-        cm.model  = beforeFirst(cm.model, L'\u00ff', IfNotFoundReturn::all);  //fix broken BIOS entries:
+        cm.model  = beforeFirst(cm.model,  L'\u00ff', IfNotFoundReturn::all); //fix broken BIOS entries:
         cm.vendor = beforeFirst(cm.vendor, L'\u00ff', IfNotFoundReturn::all); //0xff can be considered 0
 
         for (const char* dummyModel :
@@ -119,21 +116,25 @@ Zstring zen::getRealProcessPath() //throw FileError
 }
 
 
+Zstring zen::getUserDataPath() //throw FileError
+{
+    if (::getuid() != 0) //nofail; root(0) => consider as request for elevation, NOT impersonation
+        if (const char* xdgCfgPath = ::getenv("XDG_CONFIG_HOME"); //no extended error reporting
+            xdgCfgPath && xdgCfgPath[0] != 0)
+            return xdgCfgPath;
+
+    return Zstring("/home/") + utfTo<Zstring>(getUserName()) + "/.config"; //throw FileError
+}
+
+
 Zstring zen::getUserDownloadsPath() //throw FileError
 {
     try
     {
-        Zstring cmdLine;
-        if (getuid() == 0) //nofail; root(0) => consider as request for elevation, NOT impersonation
-        {
-            const char* loginUser = getlogin(); //https://linux.die.net/man/3/getlogin
-            if (!loginUser)
-                THROW_LAST_SYS_ERROR("getlogin");
-
-            cmdLine = Zstring("sudo -u ") + loginUser + " xdg-user-dir DOWNLOAD"; //sudo better be installed :>
-        }
-        else
-            cmdLine = "xdg-user-dir DOWNLOAD";
+        const Zstring cmdLine = ::getuid() == 0 ? //nofail; root(0) => consider as request for elevation, NOT impersonation
+                                //sudo better be installed :>
+                                "sudo -u " + utfTo<Zstring>(getUserName()) + " xdg-user-dir DOWNLOAD" : //throw FileError
+                                "xdg-user-dir DOWNLOAD";
 
         const auto& [exitCode, output] = consoleExecute(cmdLine, std::nullopt /*timeoutMs*/); //throw SysError
         if (exitCode != 0)
@@ -145,4 +146,3 @@ Zstring zen::getUserDownloadsPath() //throw FileError
     }
     catch (const SysError& e) { throw FileError(_("Cannot get process information."), e.toString()); }
 }
-
diff --git a/zen/sys_info.h b/zen/sys_info.h
index 1b046fb6..4f83a9a3 100644
--- a/zen/sys_info.h
+++ b/zen/sys_info.h
@@ -31,6 +31,7 @@ std::wstring getOsDescription(); //throw FileError
 Zstring getRealProcessPath(); //throw FileError
 
 Zstring getUserDownloadsPath(); //throw FileError
+Zstring getUserDataPath(); //throw FileError
 
 }
 
diff --git a/zen/thread.cpp b/zen/thread.cpp
index 89fa0233..e14afac7 100644
--- a/zen/thread.cpp
+++ b/zen/thread.cpp
@@ -28,7 +28,7 @@ const std::thread::id globalMainThreadId = std::this_thread::get_id();
 
 bool zen::runningOnMainThread()
 {
-    if (globalMainThreadId == std::thread::id()) //called during static initialization!
+    if (globalMainThreadId == std::thread::id()) //if called during static initialization!
         return true;
 
     return std::this_thread::get_id() == globalMainThreadId;
diff --git a/zen/thread.h b/zen/thread.h
index 1bea95ea..136c7a5c 100644
--- a/zen/thread.h
+++ b/zen/thread.h
@@ -173,18 +173,18 @@ public:
     void run(Function&& wi /*should throw ThreadStopRequest when needed*/, bool insertFront = false)
     {
         {
-            std::lock_guard dummy(workLoad_->lock);
+            std::lock_guard dummy(workLoad_.ref().lock);
 
             if (insertFront)
-                workLoad_->tasks.push_front(std::move(wi));
+                workLoad_.ref().tasks.push_front(std::move(wi));
             else
-                workLoad_->tasks.push_back(std::move(wi));
-            const size_t tasksPending = ++(workLoad_->tasksPending);
+                workLoad_.ref().tasks.push_back(std::move(wi));
+            const size_t tasksPending = ++(workLoad_.ref().tasksPending);
 
             if (worker_.size() < std::min(tasksPending, threadCountMax_))
                 addWorkerThread();
         }
-        workLoad_->conditionNewTask.notify_all();
+        workLoad_.ref().conditionNewTask.notify_all();
     }
 
     //context of controlling thread, blocking:
@@ -203,12 +203,12 @@ public:
     //non-blocking wait()-alternative: context of controlling thread:
     void notifyWhenDone(const std::function<void()>& onCompletion /*noexcept! runs on worker thread!*/)
     {
-        std::lock_guard dummy(workLoad_->lock);
+        std::lock_guard dummy(workLoad_.ref().lock);
 
-        if (workLoad_->tasksPending == 0)
+        if (workLoad_.ref().tasksPending == 0)
             onCompletion();
         else
-            workLoad_->onCompletionCallbacks.push_back(onCompletion);
+            workLoad_.ref().onCompletionCallbacks.push_back(onCompletion);
     }
 
     //context of controlling thread:
@@ -222,27 +222,28 @@ private:
     {
         Zstring threadName = groupName_ + Zstr('[') + numberTo<Zstring>(worker_.size() + 1) + Zstr('/') + numberTo<Zstring>(threadCountMax_) + Zstr(']');
 
-        worker_.emplace_back([wl = workLoad_, threadName = std::move(threadName)] //don't capture "this"! consider detach() and move operations
+        worker_.emplace_back([workLoad_ /*clang bug*/= workLoad_ /*share ownership!*/, threadName = std::move(threadName)]() mutable //don't capture "this"! consider detach() and move operations
         {
             setCurrentThreadName(threadName);
+            WorkLoad& workLoad = workLoad_.ref();
 
-            std::unique_lock dummy(wl->lock);
+            std::unique_lock dummy(workLoad.lock);
             for (;;)
             {
-                interruptibleWait(wl->conditionNewTask, dummy, [&tasks = wl->tasks] { return !tasks.empty(); }); //throw ThreadStopRequest
+                interruptibleWait(workLoad.conditionNewTask, dummy, [&tasks = workLoad.tasks] { return !tasks.empty(); }); //throw ThreadStopRequest
 
-                Function task = std::move(wl->tasks.    front()); //noexcept thanks to move
-                /**/                      wl->tasks.pop_front();  //
+                Function task = std::move(workLoad.tasks.    front()); //noexcept thanks to move
+                /**/                      workLoad.tasks.pop_front();  //
 
                 dummy.unlock();
                 task(); //throw ThreadStopRequest?
                 dummy.lock();
 
-                if (--(wl->tasksPending) == 0)
-                    if (!wl->onCompletionCallbacks.empty())
+                if (--(workLoad.tasksPending) == 0)
+                    if (!workLoad.onCompletionCallbacks.empty())
                     {
                         std::vector<std::function<void()>> callbacks;
-                        callbacks.swap(wl->onCompletionCallbacks);
+                        callbacks.swap(workLoad.onCompletionCallbacks);
 
                         dummy.unlock();
                         for (const auto& cb : callbacks)
@@ -263,7 +264,7 @@ private:
     };
 
     std::vector<InterruptibleThread> worker_;
-    std::shared_ptr<WorkLoad> workLoad_ = std::make_shared<WorkLoad>();
+    SharedRef<WorkLoad> workLoad_ = makeSharedRef<WorkLoad>();
     bool detach_ = false;
     size_t threadCountMax_;
     Zstring groupName_;
@@ -446,7 +447,7 @@ private:
         activeCondition_ = cv;
     }
 
-    std::atomic<bool> stopRequested_{ false }; //std:atomic is uninitialized by default!!!
+    std::atomic<bool> stopRequested_{false}; //std:atomic is uninitialized by default!!!
     //"The default constructor is trivial: no initialization takes place other than zero initialization of static and thread-local objects."
 
     std::condition_variable* activeCondition_ = nullptr;
diff --git a/zen/time.h b/zen/time.h
index aaf36983..903b2e87 100644
--- a/zen/time.h
+++ b/zen/time.h
@@ -271,7 +271,7 @@ TimeComp parseTime(const String& format, const String2& str)
                     if (strLast - itStr < 3)
                         return TimeComp();
 
-                    const char* months[] = { "jan", "feb", "mar", "apr", "may", "jun", "jul", "aug", "sep", "oct", "nov", "dec" };
+                    const char* months[] = {"jan", "feb", "mar", "apr", "may", "jun", "jul", "aug", "sep", "oct", "nov", "dec"};
                     auto itMonth = std::find_if(std::begin(months), std::end(months), [&](const char* month)
                     {
                         return equalAsciiNoCase(makeStringView(itStr, 3), month);
diff --git a/zen/type_traits.h b/zen/type_traits.h
index 03fbd768..a4194c05 100644
--- a/zen/type_traits.h
+++ b/zen/type_traits.h
@@ -20,6 +20,7 @@ struct GetFirstOf
 };
 template<class... T> using GetFirstOfT = typename GetFirstOf<T...>::Type;
 
+
 template <class F>
 class FunctionReturnType
 {
@@ -48,40 +49,40 @@ template<class T> inline auto makeSigned  (T t) { return static_cast<std::make_s
 template<class T> inline auto makeUnsigned(T t) { return static_cast<std::make_unsigned_t<T>>(t); }
 
 //################# Built-in Types  ########################
-//Example: "IsSignedInt<int>::value" evaluates to "true"
-
 //unfortunate standardized nonsense: std::is_integral<> includes bool, char, wchar_t! => roll our own:
-template <class T> struct IsUnsignedInt;
-template <class T> struct IsSignedInt;
-
-template <class T> using IsFloat      = std::is_floating_point<T>;
-template <class T> using IsInteger    = std::bool_constant<IsUnsignedInt<T>::value || IsSignedInt<T>::value>;
-template <class T> using IsArithmetic = std::bool_constant<IsInteger    <T>::value || IsFloat    <T>::value>;
-
-//remaining non-arithmetic types: bool, char, wchar_t
-
-
-//optional: specialize new types like:
-//template <> struct IsUnsignedInt<UInt64> : std::true_type {};
+template<class T> constexpr bool IsUnsignedIntV = std::is_same_v<std::remove_cv_t<T>, unsigned char>      ||
+                                                  std::is_same_v<std::remove_cv_t<T>, unsigned short int> ||
+                                                  std::is_same_v<std::remove_cv_t<T>, unsigned int>       ||
+                                                  std::is_same_v<std::remove_cv_t<T>, unsigned long int>  ||
+                                                  std::is_same_v<std::remove_cv_t<T>, unsigned long long int>;
+
+template<class T> constexpr bool IsSignedIntV = std::is_same_v<std::remove_cv_t<T>, signed char> ||
+                                                std::is_same_v<std::remove_cv_t<T>, short int>   ||
+                                                std::is_same_v<std::remove_cv_t<T>, int>         ||
+                                                std::is_same_v<std::remove_cv_t<T>, long int>    ||
+                                                std::is_same_v<std::remove_cv_t<T>, long long int>;
+
+template<class T> constexpr bool IsIntegerV    = IsUnsignedIntV<T> || IsSignedIntV<T>;
+template<class T> constexpr bool IsFloatV      = std::is_floating_point_v<T>;
+template<class T> constexpr bool IsArithmeticV = IsIntegerV<T> || IsFloatV<T>;
 
 //################# Class Members ########################
 
 /*  Detect data or function members of a class by name: ZEN_INIT_DETECT_MEMBER + HasMember_
     Example: 1. ZEN_INIT_DETECT_MEMBER(c_str);
              2. HasMemberV_c_str<T>    -> use boolean
-*/
 
-/*  Detect data or function members of a class by name *and* type: ZEN_INIT_DETECT_MEMBER2 + HasMember_
+
+    Detect data or function members of a class by name *and* type: ZEN_INIT_DETECT_MEMBER2 + HasMember_
 
     Example: 1. ZEN_INIT_DETECT_MEMBER2(size, size_t (T::*)() const);
              2. HasMember_size<T>::value    -> use as boolean
-*/
 
-/*  Detect member type of a class: ZEN_INIT_DETECT_MEMBER_TYPE + HasMemberType_
+
+    Detect member type of a class: ZEN_INIT_DETECT_MEMBER_TYPE + HasMemberType_
 
     Example: 1. ZEN_INIT_DETECT_MEMBER_TYPE(value_type);
-             2. HasMemberTypeV_value_type<T>    -> use as boolean
-*/
+             2. HasMemberTypeV_value_type<T>    -> use as boolean                       */
 
 //########## Sorting ##############################
 /*
@@ -114,25 +115,6 @@ LessDescending<Predicate> makeSortDirection(Predicate pred, std::false_type) { r
 
 
 //################ implementation ######################
-template <class T>
-struct IsUnsignedInt : std::false_type {};
-
-template <> struct IsUnsignedInt<unsigned char         > : std::true_type {};
-template <> struct IsUnsignedInt<unsigned short int    > : std::true_type {};
-template <> struct IsUnsignedInt<unsigned int          > : std::true_type {};
-template <> struct IsUnsignedInt<unsigned long int     > : std::true_type {};
-template <> struct IsUnsignedInt<unsigned long long int> : std::true_type {};
-
-template <class T>
-struct IsSignedInt : std::false_type {};
-
-template <> struct IsSignedInt<signed char  > : std::true_type {};
-template <> struct IsSignedInt<short int    > : std::true_type {};
-template <> struct IsSignedInt<int          > : std::true_type {};
-template <> struct IsSignedInt<long int     > : std::true_type {};
-template <> struct IsSignedInt<long long int> : std::true_type {};
-//####################################################################
-
 #define ZEN_INIT_DETECT_MEMBER(NAME)        \
     \
     template<bool isClass, class T>         \