enable CI for Clang

.github/workflows/windows.yml

@@ -58,7 +58,8 @@ jobs:
         shell: msys2 {0}
     strategy:
       matrix:
-        sys: [ ucrt64 ]
+        cxx: [ clang++ ]
+        lib: [ libc++, libstdc++ ]
     steps:
     - name: Set timezone
       run: tzutil /s "Ekaterinburg Standard Time"
@@ -68,10 +69,16 @@ jobs:
       with:
         release: false
         msystem: ucrt64
-        pacboy: cc:u cmake:u ninja:u lld:u clang:u
+        pacboy: cmake:u ninja:u clang:u libc++:u gcc-libs:u
     - name: Configure
-      run: cmake -B ../build -DBUILD_SHARED_LIBS=ON -DCMAKE_BUILD_TYPE=Debug
-      env: { LDFLAGS: -fuse-ld=lld }
+      run: |
+        cmake -B ../build -G "Ninja" -DCMAKE_CXX_VERSION=20 \
+        -DCMAKE_CXX_EXTENSIONS=OFF \
+        -DBUILD_SHARED_LIBS=ON -DCMAKE_BUILD_TYPE=Debug
+      env: 
+        CXX: ${{matrix.cxx}}
+        CXXFLAGS: ${{format('-stdlib={0}', matrix.lib)}}
+
     - name: Build
       run: cmake --build ../build
     - name: Test

CMakeLists.txt

@@ -34,6 +34,11 @@ function(enable_module target)
     target_compile_options(${target}
       PRIVATE /interface /dxifcInlineFunctions-
       INTERFACE /reference fmt=${BMI})
+  elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    set(BMI ${CMAKE_CURRENT_BINARY_DIR}/fmt.pcm)
+    target_compile_options(${target}
+      PRIVATE -fmodule-output=${BMI} -x c++-module
+      INTERFACE -fmodule-file=fmt=${BMI})
   endif ()
   set_target_properties(${target} PROPERTIES ADDITIONAL_CLEAN_FILES ${BMI})
   set_source_files_properties(${BMI} PROPERTIES GENERATED ON)
@@ -88,7 +93,10 @@ option(FMT_MODULE "Build a module instead of a traditional library." OFF)
 option(FMT_SYSTEM_HEADERS "Expose headers with marking them as system." OFF)
 
 set(FMT_CAN_MODULE OFF)
-if (CMAKE_CXX_STANDARD GREATER 17 AND MSVC AND MSVC_VERSION GREATER 1933)
+if (CMAKE_CXX_STANDARD GREATER 17 AND (
+  (MSVC AND MSVC_VERSION GREATER 1933) OR
+  ((CMAKE_CXX_COMPILER_ID MATCHES "Clang") AND
+   (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL "16.0"))))
   set(FMT_CAN_MODULE ON)
 endif ()
 if (NOT FMT_CAN_MODULE)