refactor: use clear stdlib naming instead of force_libstdcpp

- Rename force_libstdcpp to stdlib with values libstdcxx/libcxx
- Make stdlib a required enum field with validation
- Update cache keys to be self-documenting (e.g. clang-14-libstdcxx)
- Cleaner, more intuitive configuration flow

.github/actions/xahau-ga-build/action.yml

@@ -36,10 +36,13 @@ inputs:
     description: 'Main branch name for restore keys'
     required: false
     default: 'dev'
-  clang_use_libstdcpp:
+  stdlib:
-    description: 'Force clang to use libstdc++ instead of libc++ (workaround for clang-16)'
+    description: 'C++ standard library to use'
-    required: false
+    required: true
-    default: 'false'
+    type: choice
+    options:
+      - libstdcxx
+      - libcxx
 
 runs:
   using: 'composite'
@@ -85,12 +88,14 @@ runs:
           CCACHE_ARGS="-DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache"
         fi
         
-        # Configure libstdc++ override for clang if requested
+        # Configure C++ standard library if specified
-        # This works around clang-16 missing lexicographical_compare_three_way in libc++
+        # libstdcxx used for clang-14/16 to work around missing lexicographical_compare_three_way in libc++
-        # which is only available in LLVM 17+. Can be removed when upgrading to clang-17+
+        # libcxx can be used with clang-17+ which has full C++20 support
         STDLIB_ARGS=""
-        if [ "${{ inputs.clang_use_libstdcpp }}" = "true" ] && [[ "${{ inputs.cxx }}" == *"clang"* ]]; then
+        if [ "${{ inputs.stdlib }}" = "libstdcxx" ]; then
           STDLIB_ARGS="-DCMAKE_CXX_FLAGS=-stdlib=libstdc++"
+        elif [ "${{ inputs.stdlib }}" = "libcxx" ]; then
+          STDLIB_ARGS="-DCMAKE_CXX_FLAGS=-stdlib=libc++"
         fi
         
         # Run CMake configure

.github/actions/xahau-ga-dependencies/action.yml

@@ -25,10 +25,13 @@ inputs:
     description: 'Main branch name for restore keys'
     required: false
     default: 'dev'
-  stdlib_choice:
+  stdlib:
-    description: 'Standard library choice (affects cache key for different stdlib builds)'
+    description: 'C++ standard library - affects cache key'
-    required: false
+    required: true
-    default: 'default'
+    type: choice
+    options:
+      - libstdcxx
+      - libcxx
 
 outputs:
   cache-hit:
@@ -54,10 +57,10 @@ runs:
         path: |
           ~/.conan
           ~/.conan2
-        key: ${{ runner.os }}-conan-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.stdlib_choice }}-${{ hashFiles('**/conanfile.txt', '**/conanfile.py') }}-${{ inputs.configuration }}
+        key: ${{ runner.os }}-conan-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.stdlib }}-${{ hashFiles('**/conanfile.txt', '**/conanfile.py') }}-${{ inputs.configuration }}
         restore-keys: |
-          ${{ runner.os }}-conan-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.stdlib_choice }}-${{ hashFiles('**/conanfile.txt', '**/conanfile.py') }}-
+          ${{ runner.os }}-conan-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.stdlib }}-${{ hashFiles('**/conanfile.txt', '**/conanfile.py') }}-
-          ${{ runner.os }}-conan-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.stdlib_choice }}-
+          ${{ runner.os }}-conan-v${{ inputs.cache_version }}-${{ inputs.compiler-id }}-${{ inputs.stdlib }}-
 
     - name: Export custom recipes
       shell: bash

.github/workflows/xahau-ga-nix.yml

@@ -27,19 +27,19 @@ jobs:
           #   cxx: g++-13
           #   compiler_id: gcc-13
           #   compiler_version: 13
-          #   force_libstdcpp: false
+          #   stdlib: libstdcxx
           - compiler: clang
             cc: clang-14
             cxx: clang++-14
             compiler_id: clang-14
             compiler_version: 14
-            force_libstdcpp: true  # Required for clang-14 compatibility
+            stdlib: libstdcxx  # Required for clang-14 compatibility
           - compiler: clang
             cc: clang-16
             cxx: clang++-16
             compiler_id: clang-16
             compiler_version: 16
-            force_libstdcpp: true  # Workaround for missing lexicographical_compare_three_way in libc++
+            stdlib: libstdcxx  # Workaround for missing lexicographical_compare_three_way in libc++
     env:
       build_dir: .build
       # Bump this number to invalidate all caches globally.
@@ -72,13 +72,11 @@ jobs:
           conan profile new default --detect || true # Ignore error if profile exists
           conan profile update settings.compiler.cppstd=20 default
           conan profile update settings.compiler=${{ matrix.compiler }} default
-          # Use libstdc++11 for clang when force_libstdcpp is enabled, otherwise use libc++
+          # Set the C++ standard library based on matrix configuration
-          if [ "${{ matrix.compiler }}" = "clang" ] && [ "${{ matrix.force_libstdcpp }}" = "true" ]; then
+          if [ "${{ matrix.stdlib }}" = "libstdcxx" ]; then
             conan profile update settings.compiler.libcxx=libstdc++11 default
-          elif [ "${{ matrix.compiler }}" = "clang" ]; then
+          elif [ "${{ matrix.stdlib }}" = "libcxx" ]; then
             conan profile update settings.compiler.libcxx=libc++ default
-          else
-            conan profile update settings.compiler.libcxx=libstdc++11 default
           fi
           conan profile update env.CC=/usr/bin/${{ matrix.cc }} default
           conan profile update env.CXX=/usr/bin/${{ matrix.cxx }} default
@@ -109,7 +107,7 @@ jobs:
           compiler-id: ${{ matrix.compiler_id }}
           cache_version: ${{ env.CACHE_VERSION }}
           main_branch: ${{ env.MAIN_BRANCH_NAME }}
-          stdlib_choice: ${{ matrix.force_libstdcpp }}
+          stdlib: ${{ matrix.stdlib }}
 
       - name: Build
         uses: ./.github/actions/xahau-ga-build
@@ -122,7 +120,7 @@ jobs:
           compiler-id: ${{ matrix.compiler_id }}
           cache_version: ${{ env.CACHE_VERSION }}
           main_branch: ${{ env.MAIN_BRANCH_NAME }}
-          clang_use_libstdcpp: ${{ matrix.force_libstdcpp }}
+          stdlib: ${{ matrix.stdlib }}
 
       - name: Set artifact name
         id: set-artifact-name