diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cfe07bb4..7e5686c2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -127,6 +127,9 @@ jobs:
         run: |
           make -C build/extra/gcc-m32/debug test
           make -C build/extra/gcc-m32/release test
+      - name: 'Run file system test suite'
+        run: |
+          env -C build/extra/gcc/release bash "$PWD"/misc/testsuite/test_symlinks.sh
       - name: 'Run test suite build/extra/gcc/release'
         run: |
           export upx_testsuite_SRCDIR="$(readlink -en ../deps/upx-testsuite)"
@@ -142,6 +145,8 @@ jobs:
       fail-fast: false
       matrix:
         include:
+          # NOTE: macos does not have "env -C"; only with coreutils
+          # NOTE: macos-11 does not have "readlink -f"; only on macos >= 12 or with coreutils
           - { os: macos-11, gcc: gcc-10, gxx: 'g++-10', testsuite: true }
           - { os: macos-12, gcc: gcc-11, gxx: 'g++-11', testsuite: true }
           - { os: macos-13, gcc: gcc-12, gxx: 'g++-12', testsuite: true }
@@ -201,6 +206,14 @@ jobs:
         run: |
           make -C build/extra/clang/debug test
           make -C build/extra/clang/release test
+      - name: 'Run file system test suite'
+        if: ${{ matrix.testsuite }} # for coreutils readlink
+        run: |
+          ## macos-11 does not have "readlink -f"
+          ##   testsuite="$(readlink -fn ./misc/testsuite/test_symlinks.sh)"
+          ##   (cd build/extra/clang/release && upx_exe=./upx bash "$testsuite")
+          export PATH="/usr/local/opt/coreutils/libexec/gnubin:$PATH"
+          env -C build/extra/clang/release bash "$PWD"/misc/testsuite/test_symlinks.sh
       - name: 'Run test suite build/extra/clang/release'
         if: ${{ matrix.testsuite }}
         run: |
diff --git a/.github/workflows/weekly-ci-cc-alpine-linux.yml b/.github/workflows/weekly-ci-cc-alpine-linux.yml
index 999b7845..ad290670 100644
--- a/.github/workflows/weekly-ci-cc-alpine-linux.yml
+++ b/.github/workflows/weekly-ci-cc-alpine-linux.yml
@@ -146,6 +146,14 @@ jobs:
           (cd "upx with space"/build/xtarget/gcc-static/release   && DESTDIR="$PWD/Install with cmake" cmake --install .)
           (cd "upx with space"/build/xtarget/gcc-static/release   && DESTDIR="$PWD/Install with make"  make install)
 
+      - name: 'Run file system test suite (busybox)'
+        run: |
+          apk add bash sudo
+          testsuite="$(readlink -fn "upx with space"/misc/testsuite/test_symlinks.sh)"
+          cd "upx with space"/build/xtarget/gcc-static/release
+          # IMPORTANT: do NOT run as user root!
+          chmod a+w . && sudo -u operator bash "$testsuite"
+
       # test suite
       - name: ${{ format('Run test suite level {0}', env.UPX_TESTSUITE_LEVEL) }}
         run: |
@@ -156,3 +164,11 @@ jobs:
           export upx_testsuite_SRCDIR="$(readlink -fn "upx-testsuite with space")"
           testsuite_1="$(readlink -fn "upx with space"/misc/testsuite/upx_testsuite_1.sh)"
           (cd "upx with space"/build/xtarget/gcc-static/release && upx_exe=./upx bash "$testsuite_1")
+
+      - name: 'Run file system test suite (coreutils)'
+        run: |
+          apk add bash coreutils sudo
+          testsuite="$(readlink -fn "upx with space"/misc/testsuite/test_symlinks.sh)"
+          cd "upx with space"/build/xtarget/gcc-static/release
+          # IMPORTANT: do NOT run as user root!
+          chmod a+w . && sudo -u operator bash "$testsuite"
diff --git a/misc/testsuite/test_symlinks.sh b/misc/testsuite/test_symlinks.sh
new file mode 100755
index 00000000..c1abb5ce
--- /dev/null
+++ b/misc/testsuite/test_symlinks.sh
@@ -0,0 +1,373 @@
+#! /usr/bin/env bash
+## vim:set ts=4 sw=4 et:
+set -e; set -o pipefail
+argv0=$0; argv0abs=$(readlink -fn "$argv0"); argv0dir=$(dirname "$argv0abs")
+
+# IMPORTANT NOTE: do NOT run as user root!!
+# IMPORTANT NOTE: this script only works on Unix!!
+umask 0022
+
+id || true
+if [[ $UID == 0 || $EUID == 0 ]]; then
+    echo "ERROR: do not run as root: UID=$UID EUID=$EUID"
+    exit 91
+fi
+
+# test behaviour with symlinks; requires:
+#   $upx_exe                (required, but with convenience fallback "./upx")
+# optional settings:
+#   $upx_exe_runner         (e.g. "qemu-x86_64 -cpu Westmere" or "valgrind")
+
+#***********************************************************************
+# init & checks
+#***********************************************************************
+
+# upx_exe
+[[ -z $upx_exe && -f ./upx && -x ./upx ]] && upx_exe=./upx # convenience fallback
+if [[ -z $upx_exe ]]; then echo "UPX-ERROR: please set \$upx_exe"; exit 1; fi
+if [[ ! -f $upx_exe ]]; then echo "UPX-ERROR: file '$upx_exe' does not exist"; exit 1; fi
+upx_exe=$(readlink -fn "$upx_exe") # make absolute
+[[ -f $upx_exe ]] || exit 1
+upx_run=()
+if [[ -n $upx_exe_runner ]]; then
+    # usage examples:
+    #   export upx_exe_runner="qemu-x86_64 -cpu Westmere"
+    #   export upx_exe_runner="valgrind --leak-check=no --error-exitcode=1 --quiet"
+    #   export upx_exe_runner="wine"
+    IFS=' ' read -r -a upx_run <<< "$upx_exe_runner" # split at spaces into array
+fi
+upx_run+=( "$upx_exe" )
+echo "upx_run='${upx_run[*]}'"
+
+# upx_run check, part1
+if ! "${upx_run[@]}" --version-short >/dev/null; then echo "UPX-ERROR: FATAL: upx --version-short FAILED"; exit 1; fi
+if ! "${upx_run[@]}" -L >/dev/null 2>&1; then echo "UPX-ERROR: FATAL: upx -L FAILED"; exit 1; fi
+if ! "${upx_run[@]}" --help >/dev/null;  then echo "UPX-ERROR: FATAL: upx --help FAILED"; exit 1; fi
+
+#***********************************************************************
+#
+#***********************************************************************
+
+failed() {
+    ####exit $1
+    # log error and keep going
+    exit_code=1
+    local a="$(basename "$(dirname "$PWD")")"
+    local b="$(basename "$PWD")"
+    let num_errors+=1 || true
+    all_errors="${all_errors} $a/$b/$1"
+    echo "    FAILED $b/$1"
+}
+
+assert_file() {
+    local f
+    for f in "$@"; do
+        [[ ! -L "$f" && -f "$f" ]] && continue
+        echo "failed '$f': not a regular file"
+        failed 21
+    done
+}
+
+assert_symlink_to_file() {
+    local f
+    for f in "$@"; do
+        [[ -L "$f" && -f "$f" ]] && continue
+        echo "failed '$f': not a symlink to file"
+        failed 22
+    done
+}
+
+assert_symlink_to_dir() {
+    local f
+    for f in "$@"; do
+        [[ -L "$f" && -d "$f" ]] && continue
+        echo "failed '$f': not a symlink to dir"
+        failed 23
+    done
+}
+
+assert_symlink_dangling() {
+    local f
+    for f in "$@"; do
+        [[ -L "$f" && ! -e "$f" ]] && continue
+        echo "failed '$f': not a dangling symlink"
+        failed 24
+    done
+}
+
+create_files() {
+    # clean
+    for d in z_dir_1 z_dir_2 z_dir_3 z_dir_4; do
+        if [[ -d $d ]]; then
+            chmod -R +w "./$d"
+            rm -rf "./$d"
+        fi
+    done
+
+    mkdir z_dir_1
+    cd z_dir_1
+    : > z_file
+    ln -s z_file z_symlink_file
+    : > z_file_link_1
+    ln z_file_link_1 z_file_link_2
+    ln -s z_file_link_1 z_symlink_file_link
+    mkdir z_dir
+    ln -s z_dir z_symlink_dir
+    ln -s z_file_missing z_symlink_dangling
+    assert_file             z_file*
+    assert_symlink_to_file  z_symlink_file
+    assert_symlink_to_dir   z_symlink_dir
+    assert_symlink_dangling z_symlink_dangling
+    cd ..
+
+    # write-protect z_dir_2/z_file*
+    cp -ai z_dir_1 z_dir_2
+    chmod a-w z_dir_2/z_file*
+
+    # write-protect z_dir_3 itself
+    cp -ai z_dir_1 z_dir_3
+    chmod a-w z_dir_3
+
+    # write-protect everything in z_dir_4
+    cp -ai z_dir_1 z_dir_4
+    chmod -R a-w z_dir_4
+}
+
+#***********************************************************************
+#
+#***********************************************************************
+
+export UPX="--prefer-ucl --no-color --no-progress"
+export UPX_DEBUG_DISABLE_GITREV_WARNING=1
+export UPX_DEBUG_DOCTEST_VERBOSE=0
+export NO_COLOR=1
+
+#set -x # debug
+exit_code=0
+num_errors=0
+all_errors=
+
+testsuite_header() {
+    local x='==========='; x="$x$x$x$x$x$x$x"
+    echo -e "\n${x}\n${1}\n${x}\n"
+}
+
+enter_dir() {
+    cd "$1" || exit 1
+    echo "===== $(basename "$PWD")"
+}
+leave_dir() {
+    echo "===== $(basename "$PWD") files"
+    ls -lA
+    cd ..
+}
+
+# create a tmpdir in current directory
+tmpdir="$(mktemp -d tmp-upx-test-XXXXXX)"
+cd "./$tmpdir" || exit 1
+
+test_file="$(readlink -fn /bin/ls)"
+
+testsuite_header "default"
+flags="-qq -1 --no-filter"
+mkdir default
+cd default
+create_files
+enter_dir z_dir_1
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          || failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              && failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       && failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      && failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link && failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       && failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  && failed 18
+assert_symlink_to_file  z_symlink_file z_symlink_file_link
+assert_symlink_to_dir   z_symlink_dir
+assert_symlink_dangling z_symlink_dangling
+leave_dir
+enter_dir z_dir_2
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          || failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              && failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       && failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      && failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link && failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       && failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  && failed 18
+assert_symlink_to_file  z_symlink_file z_symlink_file_link
+assert_symlink_to_dir   z_symlink_dir
+assert_symlink_dangling z_symlink_dangling
+leave_dir
+enter_dir z_dir_3
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          && failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              && failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       && failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      && failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link && failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       && failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  && failed 18
+assert_symlink_to_file  z_symlink_file z_symlink_file_link
+assert_symlink_to_dir   z_symlink_dir
+assert_symlink_dangling z_symlink_dangling
+leave_dir
+enter_dir z_dir_4
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          && failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              && failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       && failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      && failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link && failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       && failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  && failed 18
+assert_symlink_to_file  z_symlink_file z_symlink_file_link
+assert_symlink_to_dir   z_symlink_dir
+assert_symlink_dangling z_symlink_dangling
+leave_dir
+cd ..
+
+testsuite_header "force-overwrite"
+flags="-qq -1 --no-filter --force-overwrite"
+mkdir force-overwrite
+cd force-overwrite
+create_files
+enter_dir z_dir_1
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          || failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              || failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       || failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      || failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link || failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       || failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  || failed 18
+assert_file z_symlink_file z_symlink_file_link
+assert_file z_symlink_dir
+assert_file z_symlink_dangling
+leave_dir
+enter_dir z_dir_2
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          || failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              || failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       || failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      || failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link || failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       || failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  || failed 18
+assert_file z_symlink_file z_symlink_file_link
+assert_file z_symlink_dir
+assert_file z_symlink_dangling
+leave_dir
+enter_dir z_dir_3
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          && failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              || failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       || failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      || failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link || failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       && failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  && failed 18
+assert_symlink_to_file  z_symlink_file z_symlink_file_link
+assert_symlink_to_dir   z_symlink_dir
+assert_symlink_dangling z_symlink_dangling
+leave_dir
+enter_dir z_dir_4
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          && failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              || failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       || failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      || failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link || failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       && failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  && failed 18
+assert_symlink_to_file  z_symlink_file z_symlink_file_link
+assert_symlink_to_dir   z_symlink_dir
+assert_symlink_dangling z_symlink_dangling
+leave_dir
+cd ..
+
+if [[ 1 == 1 ]]; then
+testsuite_header "link"
+flags="-qq -1 --no-filter --link"
+mkdir link
+cd link
+create_files
+enter_dir z_dir_1
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          || failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              || failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       || failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      || failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link || failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       || failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  || failed 18
+assert_file z_symlink_file z_symlink_file_link
+assert_file z_symlink_dir
+assert_file z_symlink_dangling
+leave_dir
+enter_dir z_dir_2
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          || failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              && failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       && failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      || failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link || failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       || failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  || failed 18
+assert_file z_symlink_file z_symlink_file_link
+assert_file z_symlink_dir
+assert_file z_symlink_dangling
+leave_dir
+enter_dir z_dir_3
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          && failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              || failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       || failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      || failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link || failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       && failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  && failed 18
+assert_symlink_to_file  z_symlink_file z_symlink_file_link
+assert_symlink_to_dir   z_symlink_dir
+assert_symlink_dangling z_symlink_dangling
+leave_dir
+enter_dir z_dir_4
+"${upx_run[@]}" $flags                 z_symlink_file      && failed 10
+"${upx_run[@]}" $flags "$test_file" -o z_file_new          && failed 11
+"${upx_run[@]}" $flags "$test_file" -o z_dir               && failed 12
+"${upx_run[@]}" $flags "$test_file" -o z_file              && failed 13
+"${upx_run[@]}" $flags "$test_file" -o z_file_link_1       && failed 14
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file      || failed 15
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_file_link || failed 16
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dir       && failed 17
+"${upx_run[@]}" $flags "$test_file" -o z_symlink_dangling  && failed 18
+assert_symlink_to_file  z_symlink_file z_symlink_file_link
+assert_symlink_to_dir   z_symlink_dir
+assert_symlink_dangling z_symlink_dangling
+leave_dir
+cd ..
+fi
+
+# clean up
+cd ..
+chmod -R +w "./$tmpdir"
+rm -rf "./$tmpdir"
+
+if [[ $exit_code == 0 ]]; then
+    echo "UPX testsuite passed. All done."
+else
+    echo "UPX-ERROR: UPX testsuite FAILED:${all_errors}"
+    echo "UPX-ERROR: UPX testsuite FAILED with $num_errors error(s). See log file."
+fi
+exit $exit_code
diff --git a/misc/testsuite/upx_testsuite_1.sh b/misc/testsuite/upx_testsuite_1.sh
index a75d0261..2e67e82e 100755
--- a/misc/testsuite/upx_testsuite_1.sh
+++ b/misc/testsuite/upx_testsuite_1.sh
@@ -15,9 +15,9 @@ argv0=$0; argv0abs=$(readlink -fn "$argv0"); argv0dir=$(dirname "$argv0abs")
 #
 # see https://github.com/upx/upx-testsuite.git
 
-# /***********************************************************************
-# // init & checks
-# ************************************************************************/
+#***********************************************************************
+# init & checks
+#***********************************************************************
 
 # upx_exe
 [[ -z $upx_exe && -f ./upx && -x ./upx ]] && upx_exe=./upx # convenience fallback
@@ -91,9 +91,9 @@ if [[ $UPX_TESTSUITE_LEVEL == 0 ]]; then
     exit 0
 fi
 
-# /***********************************************************************
-# // setup
-# ************************************************************************/
+#***********************************************************************
+# setup
+#***********************************************************************
 
 #set -x # debug
 exit_code=0
@@ -103,15 +103,14 @@ all_errors=
 export UPX="--prefer-ucl --no-color --no-progress"
 export UPX_DEBUG_DISABLE_GITREV_WARNING=1
 export UPX_DEBUG_DOCTEST_VERBOSE=0
-export NO_COLOR=1
 
 rm -rf ./testsuite_1
 mkdir testsuite_1 || exit 1
 cd testsuite_1 || exit 1
 
-# /***********************************************************************
-# // support functions
-# ************************************************************************/
+#***********************************************************************
+# support functions
+#***********************************************************************
 
 run_upx() {
     local ec=0
@@ -195,13 +194,13 @@ testsuite_run_compress() {
     fi
 }
 
-# /***********************************************************************
-# // expected checksums
-# //
-# // To ease maintenance of this script in case of updates this section
-# // can be automatically re-created from the current checksums -
-# // see call of function recreate_expected_sha256sums below.
-# ************************************************************************/
+#***********************************************************************
+# expected checksums
+#
+# To ease maintenance of this script in case of updates this section
+# can be automatically re-created from the current checksums -
+# see call of function recreate_expected_sha256sums below.
+#***********************************************************************
 
 recreate_expected_sha256sums() {
     local o="$1"
@@ -219,9 +218,9 @@ recreate_expected_sha256sums() {
 
 source "$argv0dir/upx_testsuite_1-expected_sha256sums.sh" || exit 1
 
-# /***********************************************************************
-# // decompression tests
-# ************************************************************************/
+#***********************************************************************
+# decompression tests
+#***********************************************************************
 
 testdir=t010_decompressed
 mkdir $testdir; v=expected_sha256sums__$testdir; echo -n "${!v}" >$testdir/.sha256sums.expected
@@ -251,11 +250,11 @@ for f in t010_decompressed/*/*; do
 done
 testsuite_check_sha $testdir
 
-# /***********************************************************************
-# // compression tests
-# // info: we use fast compression levels because we want to
-# //   test UPX and not the compression libraries
-# ************************************************************************/
+#***********************************************************************
+# compression tests
+# info: we use fast compression levels because we want to
+#   test UPX and not the compression libraries
+#***********************************************************************
 
 if [[ $UPX_TESTSUITE_LEVEL -ge 2 ]]; then
 testdir=t110_compress_ucl_nrv2b_3_no_filter
@@ -299,9 +298,9 @@ mkdir $testdir; v=expected_sha256sums__$testdir; echo -n "${!v}" >$testdir/.sha2
 time testsuite_run_compress --all-methods --no-lzma -5 --no-filter
 fi
 
-# /***********************************************************************
-# // summary
-# ************************************************************************/
+#***********************************************************************
+# summary
+#***********************************************************************
 
 # recreate checksums from current version for an easy update in case of changes
 recreate_expected_sha256sums .sha256sums.recreate
diff --git a/src/conf.h b/src/conf.h
index 11ff613b..465aec9b 100644
--- a/src/conf.h
+++ b/src/conf.h
@@ -187,13 +187,15 @@ typedef upx_int64_t upx_off_t;
 #undef small
 #undef tos
 #undef unix
-#if defined(__linux__) && !defined(__unix__)
+#if (ACC_OS_POSIX) && !defined(__unix__)
 #  define __unix__ 1
 #endif
+#if (ACC_OS_CYGWIN || ACC_OS_DOS16 || ACC_OS_DOS32 || ACC_OS_EMX || ACC_OS_OS2 || ACC_OS_OS216 || ACC_OS_WIN16 || ACC_OS_WIN32 || ACC_OS_WIN64)
+#  undef __unix
+#  undef __unix__
+#endif
 #if (ACC_OS_DOS32) && defined(__DJGPP__)
 #  undef sopen
-#  undef __unix
-#  undef __unix__
 #endif
 
 #if defined(HAVE_DUP) && (HAVE_DUP + 0 == 0)
diff --git a/src/help.cpp b/src/help.cpp
index d9392387..89029ad3 100644
--- a/src/help.cpp
+++ b/src/help.cpp
@@ -225,7 +225,7 @@ void show_help(int verbose) {
         fg = con_fg(f, fg);
         con_fprintf(f,
                     "  --force-overwrite   force overwrite of output files\n"
-#if defined(__unix__) && !defined(__MSYS2__)
+#if defined(__unix__)
                     "  --link              preserve hard links (Unix only) [USE WITH CARE]\n"
                     "  --no-link           do not preserve hard links but rename files [default]\n"
 #endif
diff --git a/src/main.cpp b/src/main.cpp
index 87224800..e9118f17 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -201,7 +201,8 @@ static void check_and_update_options(int i, int argc) {
     check_not_both(opt->force_overwrite, opt->preserve_link, "--force-overwrite", "--link");
     check_not_both(opt->to_stdout, opt->preserve_link, "--stdout", "--link");
 
-#if defined(__unix__) && !defined(__MSYS2__)
+#if defined(__unix__)
+    static_assert(HAVE_LSTAT);
 #else
     // preserve_link is currently silently ignored on non-Unix platforms
     // (we may revisit this decision later if there is some actual use-case)
diff --git a/src/p_unix.cpp b/src/p_unix.cpp
index a9dfbe2d..8b4b0c6f 100644
--- a/src/p_unix.cpp
+++ b/src/p_unix.cpp
@@ -72,7 +72,7 @@ tribool PackUnix::canPack()
     if (exetype == 0)
         return false;
 
-#if defined(__unix__) && !defined(__MSYS2__)
+#if defined(__unix__)
     // must be executable by owner
     if ((fi->st.st_mode & S_IXUSR) == 0)
         throwCantPack("file not executable; try 'chmod +x'");