diff --git a/.github/workflows/CI-unixish.yml b/.github/workflows/CI-unixish.yml
index adb91138..89f7f336 100644
--- a/.github/workflows/CI-unixish.yml
+++ b/.github/workflows/CI-unixish.yml
@@ -36,10 +36,10 @@ jobs:
           sudo apt-get install valgrind
 
     - name: Install missing software on ubuntu (clang++)
-      if: matrix.os == 'ubuntu-24.04' && matrix.compiler == 'clang++'
+      if: contains(matrix.os, 'ubuntu') && matrix.compiler == 'clang++'
       run: |
         sudo apt-get update
-        sudo apt-get install libc++-18-dev
+        sudo apt-get install libc++-dev
 
       # coreutils contains "nproc"
     - name: Install missing software on macos
diff --git a/.github/workflows/CI-windows.yml b/.github/workflows/CI-windows.yml
deleted file mode 100644
index 767bba6c..00000000
--- a/.github/workflows/CI-windows.yml
+++ /dev/null
@@ -1,66 +0,0 @@
-# Some convenient links:
-# - https://github.com/actions/virtual-environments/blob/master/images/win/Windows2019-Readme.md
-#
-
-name: CI-windows
-
-on: [push,pull_request]
-
-permissions:
-  contents: read
-
-defaults:
-  run:
-    shell: cmd
-    
-jobs:
-
-  build:
-    strategy:
-      matrix:
-        os: [windows-2022, windows-2025]
-        config: [Release, Debug]
-      fail-fast: false
-
-    runs-on: ${{ matrix.os }}
-
-    steps:
-      - uses: actions/checkout@v4
-        with:
-          persist-credentials: false
-
-      - name: Setup msbuild.exe
-        uses: microsoft/setup-msbuild@v2
-
-      - name: Set up Python 3.13
-        uses: actions/setup-python@v5
-        with:
-          python-version: '3.13'
-          check-latest: true
-
-      - name: Install missing Python packages
-        run: |
-          python -m pip install pip --upgrade || exit /b !errorlevel!
-          python -m pip install pytest || exit /b !errorlevel!
-
-      - name: Run CMake
-        run: |
-          cmake -G "Visual Studio 17 2022" -A x64 -DCMAKE_COMPILE_WARNING_AS_ERROR=On . || exit /b !errorlevel!
-
-      - name: Build
-        run: |
-           msbuild -m simplecpp.sln /p:Configuration=${{ matrix.config }} /p:Platform=x64 || exit /b !errorlevel!
-           
-      - name: Test
-        run: |
-          .\${{ matrix.config }}\testrunner.exe || exit /b !errorlevel!
-
-      - name: Selfcheck
-        run: |
-          .\${{ matrix.config }}\simplecpp.exe simplecpp.cpp -e || exit /b !errorlevel!
-
-      - name: integration test
-        run: |
-          set SIMPLECPP_EXE_PATH=.\${{ matrix.config }}\simplecpp.exe
-          python -m pytest integration_test.py -vv || exit /b !errorlevel!
-        
diff --git a/.github/workflows/clang-tidy.yml b/.github/workflows/clang-tidy.yml
deleted file mode 100644
index fd71bdfe..00000000
--- a/.github/workflows/clang-tidy.yml
+++ /dev/null
@@ -1,44 +0,0 @@
-# Syntax reference https://help.github.com/en/actions/reference/workflow-syntax-for-github-actions
-# Environment reference https://help.github.com/en/actions/reference/virtual-environments-for-github-hosted-runners
-name: clang-tidy
-
-on: [push, pull_request]
-
-permissions:
-  contents: read
-
-jobs:
-  build:
-
-    runs-on: ubuntu-24.04
-
-    steps:
-      - uses: actions/checkout@v4
-        with:
-          persist-credentials: false
-
-      - name: Install missing software
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y cmake make
-
-      - name: Install clang
-        run: |
-          wget https://apt.llvm.org/llvm.sh
-          chmod +x llvm.sh
-          sudo ./llvm.sh 20
-          sudo apt-get install clang-tidy-20
-
-      - name: Verify clang-tidy configuration
-        run: |
-          clang-tidy-20 --verify-config
-
-      - name: Prepare CMake
-        run: |
-          cmake -S . -B cmake.output -G "Unix Makefiles" -DCMAKE_COMPILE_WARNING_AS_ERROR=On -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
-        env:
-          CXX: clang-20
-
-      - name: Clang-Tidy
-        run: |
-          run-clang-tidy-20 -q -j $(nproc) -p=cmake.output
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
deleted file mode 100644
index 4d5657f8..00000000
--- a/.github/workflows/format.yml
+++ /dev/null
@@ -1,62 +0,0 @@
-# Syntax reference https://help.github.com/en/actions/reference/workflow-syntax-for-github-actions
-# Environment reference https://help.github.com/en/actions/reference/virtual-environments-for-github-hosted-runners
-name: format
-
-on:
-  push:
-    branches:
-      - 'master'
-      - 'releases/**'
-      - '1.*'
-    tags:
-      - '1.*'
-  pull_request:
-
-permissions:
-  contents: read
-
-jobs:
-  format:
-
-    runs-on: ubuntu-22.04
-
-    defaults:
-      run:
-        shell: bash -euo pipefail {0}
-
-    env:
-      UNCRUSTIFY_INSTALL_DIR: ${{ github.workspace }}/runformat-uncrustify
-
-    steps:
-      - uses: actions/checkout@v5
-        with:
-          persist-credentials: false
-
-      - name: Determine uncrustify version
-        id: get-uncrustify-version
-        run: |
-          version="$(./runformat --expected-uncrustify-version)"
-          echo "Expected uncrustify version: $version"
-          echo "version=$version" >> "$GITHUB_OUTPUT"
-
-      - name: Set UNCRUSTIFY_VERSION env variable
-        run: |
-          version=$(./runformat --expected-uncrustify-version)
-          echo "version [$version]"
-          echo "UNCRUSTIFY_VERSION=${version}" >> "$GITHUB_ENV"
-
-      - name: Cache uncrustify
-        uses: actions/cache@v4
-        id: cache-uncrustify
-        with:
-          path: ${{ env.UNCRUSTIFY_INSTALL_DIR }}
-          key: ${{ runner.os }}-uncrustify-${{ steps.get-uncrustify-version.outputs.version }}
-
-      - name: Install uncrustify
-        if: steps.cache-uncrustify.outputs.cache-hit != 'true'
-        run: |
-          ./runformat --install --install-dir "${UNCRUSTIFY_INSTALL_DIR}"
-
-      - name: Uncrustify check
-        run: |
-          ./runformat
diff --git a/Makefile b/Makefile
index 7489ec83..b6bc26da 100644
--- a/Makefile
+++ b/Makefile
@@ -22,7 +22,7 @@ test:	testrunner	simplecpp
 	python3 -m pytest integration_test.py -vv
 
 selfcheck:	simplecpp
-	./selfcheck.sh
+	CXX=$(CXX) ./selfcheck.sh
 
 simplecpp:	main.o simplecpp.o
 	$(CXX) $(LDFLAGS) main.o simplecpp.o -o simplecpp
diff --git a/main.cpp b/main.cpp
index a6d14386..747f041b 100644
--- a/main.cpp
+++ b/main.cpp
@@ -43,6 +43,11 @@ int main(int argc, char **argv)
             }
             case 'I': { // include path
                 const char * const value = arg[2] ? (argv[i] + 2) : argv[++i];
+                std::ifstream f(value);
+                if (!f.is_open()) {
+                    std::cout << "error: include path '" << value << "' does not exist" << std::endl;
+                    std::exit(1);
+                }
                 dui.includePaths.push_back(value);
                 found = true;
                 break;
diff --git a/selfcheck.sh b/selfcheck.sh
index a43ef8c5..c6fbc906 100755
--- a/selfcheck.sh
+++ b/selfcheck.sh
@@ -4,8 +4,104 @@ output=$(./simplecpp simplecpp.cpp -e -f 2>&1)
 ec=$?
 errors=$(echo "$output" | grep -v 'Header not found: <')
 if [ $ec -ne 0 ]; then
-  # only fail if got errors which do not refer to missing system includes
+  # only fail if we got errors which do not refer to missing system includes
   if [ ! -z "$errors" ]; then
     exit $ec
   fi
-fi
\ No newline at end of file
+fi
+
+if [ -z "$CXX" ]; then
+  exit 0
+fi
+
+cxx_type=$($CXX --version | head -1 | cut -d' ' -f1)
+if [ "$cxx_type" = "Ubuntu" ]; then
+  cxx_type=$($CXX --version | head -1 | cut -d' ' -f2)
+fi
+# TODO: how to get built-in include paths from compiler?
+if [ "$cxx_type" = "g++" ]; then
+  gcc_ver=$($CXX -dumpversion)
+  defs=
+  defs="$defs -D__GNUC__"
+  defs="$defs -D__STDC__"
+  defs="$defs -D__STDC_HOSTED__"
+  defs="$defs -D__CHAR_BIT__=8"
+  defs="$defs -D__x86_64__"
+  defs="$defs -D__has_builtin(x)=(1)"
+  defs="$defs -D__has_cpp_attribute(x)=(1)"
+  defs="$defs -D__has_attribute(x)=(1)"
+  # some required include paths might differ per distro
+  inc=
+  inc="$inc -I/usr/include"
+  inc="$inc -I/usr/include/linux"
+  inc="$inc -I/usr/include/c++/$gcc_ver"
+  if [ -d "/usr/include/c++/$gcc_ver/x86_64-pc-linux-gnu" ]; then
+    inc="$inc -I/usr/include/c++/$gcc_ver/x86_64-pc-linux-gnu"
+  fi
+  if [ -d "/usr/lib/gcc/x86_64-pc-linux-gnu/$gcc_ver/include" ]; then
+    inc="$inc -I/usr/lib/gcc/x86_64-pc-linux-gnu/$gcc_ver/include"
+  fi
+  if [ -d "/usr/lib/gcc/x86_64-linux-gnu/$gcc_ver/include" ]; then
+    inc="$inc -I/usr/lib/gcc/x86_64-linux-gnu/$gcc_ver/include"
+  fi
+  if [ -d "/usr/include/x86_64-linux-gnu" ]; then
+    inc="$inc -I/usr/include/x86_64-linux-gnu"
+    inc="$inc -I/usr/include/x86_64-linux-gnu/c++/$gcc_ver"
+  fi
+elif [ "$cxx_type" = "clang" ]; then
+  clang_ver=$($CXX -dumpversion)
+  clang_ver=${clang_ver%%.*}
+  defs=
+  defs="$defs -D__BYTE_ORDER__"
+  defs="$defs -D__linux__"
+  defs="$defs -D__x86_64__"
+  defs="$defs -D__SIZEOF_SIZE_T__=8"
+  defs="$defs -D__has_feature(x)=(1)"
+  defs="$defs -D__has_extension(x)=(1)"
+  defs="$defs -D__has_attribute(x)=(0)"
+  defs="$defs -D__has_cpp_attribute(x)=(0)"
+  defs="$defs -D__has_include_next(x)=(0)"
+  defs="$defs -D__has_builtin(x)=(1)"
+  # some required include paths might differ per distro
+  inc=
+  if [ -d "/usr/include/c++/v1" ]; then
+    inc="$inc -I/usr/include/c++/v1"
+  fi
+  if [ -d "/usr/lib/llvm-$clang_ver/include/c++/v1" ]; then
+    inc="$inc -I/usr/lib/llvm-$clang_ver/include/c++/v1"
+  fi
+  inc="$inc -I/usr/include"
+  inc="$inc -I/usr/lib/clang/$clang_ver/include"
+  if [ -d "/usr/include/x86_64-linux-gnu" ]; then
+    inc="$inc -I/usr/include/x86_64-linux-gnu"
+  fi
+elif [ "$cxx_type" = "Apple" ]; then
+  xcode_path="/Applications/Xcode_16.4.app"
+  if [ ! -d "$xcode_path" ]; then
+    xcode_path="/Applications/Xcode_15.2.app"
+  fi
+  sdk_path="$xcode_path/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk"
+  defs=
+  defs="$defs -D__BYTE_ORDER__"
+  defs="$defs -D__APPLE__"
+  defs="$defs -D__GNUC__=15"
+  defs="$defs -D__x86_64__"
+  defs="$defs -D__has_feature(x)=(1)"
+  defs="$defs -D__has_extension(x)=(1)"
+  defs="$defs -D__has_attribute(x)=(0)"
+  defs="$defs -D__has_cpp_attribute(x)=(0)"
+  defs="$defs -D__has_include_next(x)=(0)"
+  inc=
+  inc="$inc -I$sdk_path/usr/include/c++/v1"
+  inc="$inc -I$sdk_path/usr/include"
+  inc="$inc -I$sdk_path/usr/include/i386"
+else
+  echo "unknown compiler '$cxx_type'"
+  exit 1
+fi
+
+./simplecpp simplecpp.cpp -e -f -std=gnu++11 $defs $inc
+ec=$?
+if [ $ec -ne 0 ]; then
+  exit $ec
+fi