fix: add is_clang utility

src/Clang.cmake

@@ -0,0 +1,50 @@
+include_guard()
+
+set(ProjectOptions_SRC_DIR "${CMAKE_CURRENT_LIST_DIR}")
+
+# detect clang
+function(is_clang value)
+  if(clang
+     OR ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND "${CMAKE_C_COMPILER_ID}" STREQUAL "Clang")
+     OR ("${DETECTED_CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND "${DETECTED_CMAKE_C_COMPILER_ID}"
+                                                                  STREQUAL "Clang")
+  )
+    set(${value} ON PARENT_SCOPE)
+    return()
+  endif()
+
+  # if the compiler is unknown by CMake
+  if(NOT CMAKE_CXX_COMPILER
+     AND NOT CMAKE_C_COMPILER
+     AND NOT CMAKE_CXX_COMPILER_ID
+     AND NOT CMAKE_C_COMPILER_ID
+  )
+
+    # if clang is inferred by cmake later
+    include("${ProjectOptions_SRC_DIR}/DetectCompiler.cmake")
+    detect_compiler()
+
+    if((DETECTED_CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND DETECTED_CMAKE_C_COMPILER_ID STREQUAL
+                                                            "Clang")
+    )
+      set(${value} ON PARENT_SCOPE)
+      return()
+    endif()
+
+  endif()
+
+  set(${value} OFF PARENT_SCOPE)
+endfunction()
+
+# configure clang toolchain for vcpkg
+macro(configure_clang_vcpkg)
+  if(WIN32)
+    is_clang(_is_clang)
+    if(${_is_clang})
+      # Disable /utf-8 flag in the vcpkg toolchain file
+      # https://github.com/microsoft/vcpkg/blob/e590c2b30c08caf1dd8d612ec602a003f9784b7d/scripts/toolchains/windows.cmake#L68
+      message(STATUS "Disabling /utf-8 flag in the vcpkg toolchain file for Clang")
+      set(VCPKG_SET_CHARSET_FLAG "OFF" CACHE STRING "Vcpkg set charset flag" FORCE)
+    endif()
+  endif()
+endmacro()

src/DetectCompiler.cmake

@@ -5,30 +5,41 @@ set(ProjectOptions_SRC_DIR "${CMAKE_CURRENT_LIST_DIR}")
 # includes a separate CMakeLists.txt file to detect the CXX/C compilers before project is called
 # Using a separate file ensures that the current scope is not contaminated by the variable
 macro(detect_compiler)
-  find_program(CMAKE_EXECUTABLE cmake)
-  execute_process(
-    COMMAND
-      "${CMAKE_EXECUTABLE}" -S "${ProjectOptions_SRC_DIR}/detect_compiler" -B
-      "${CMAKE_CURRENT_BINARY_DIR}/detect_compiler" -G "${CMAKE_GENERATOR}" "--log-level=ERROR"
-      "-Wno-dev"
-    OUTPUT_QUIET
+  if(NOT
+     (DETECTED_CMAKE_CXX_COMPILER
+      AND DETECTED_CMAKE_C_COMPILER
+      AND DETECTED_CMAKE_CXX_COMPILER_ID
+      AND DETECTED_CMAKE_C_COMPILER_ID
+      AND DETECTED_CMAKE_SYSTEM_PROCESSOR
+      AND DETECTED_CMAKE_HOST_SYSTEM_PROCESSOR)
   )
 
-  # parse the detected compilers from the cache
-  set(cache_variables
-      CMAKE_CXX_COMPILER
-      CMAKE_CXX_COMPILER_ID
-      CMAKE_C_COMPILER
-      CMAKE_C_COMPILER_ID
-      CMAKE_SYSTEM_PROCESSOR
-      CMAKE_HOST_SYSTEM_PROCESSOR
-  )
-  foreach(cache_var ${cache_variables})
-    file(STRINGS "${CMAKE_CURRENT_BINARY_DIR}/detect_compiler/CMakeCache.txt"
-         "DETECTED_${cache_var}" REGEX "^${cache_var}:STRING=(.*)$"
+    find_program(CMAKE_EXECUTABLE cmake)
+    execute_process(
+      COMMAND
+        "${CMAKE_EXECUTABLE}" -S "${ProjectOptions_SRC_DIR}/detect_compiler" -B
+        "${CMAKE_CURRENT_BINARY_DIR}/detect_compiler" -G "${CMAKE_GENERATOR}" "--log-level=ERROR"
+        "-Wno-dev"
+      OUTPUT_QUIET
     )
-    string(REGEX REPLACE "^${cache_var}:STRING=(.*)$" "\\1" "DETECTED_${cache_var}"
-                         "${DETECTED_${cache_var}}"
+
+    # parse the detected compilers from the cache
+    set(cache_variables
+        CMAKE_CXX_COMPILER
+        CMAKE_CXX_COMPILER_ID
+        CMAKE_C_COMPILER
+        CMAKE_C_COMPILER_ID
+        CMAKE_SYSTEM_PROCESSOR
+        CMAKE_HOST_SYSTEM_PROCESSOR
     )
-  endforeach()
+    foreach(cache_var ${cache_variables})
+      file(STRINGS "${CMAKE_CURRENT_BINARY_DIR}/detect_compiler/CMakeCache.txt"
+           "DETECTED_${cache_var}" REGEX "^${cache_var}:STRING=(.*)$"
+      )
+      string(REGEX REPLACE "^${cache_var}:STRING=(.*)$" "\\1" "DETECTED_${cache_var}"
+                           "${DETECTED_${cache_var}}"
+      )
+    endforeach()
+
+  endif()
 endmacro()

src/Index.cmake

@@ -38,6 +38,7 @@ include("${ProjectOptions_SRC_DIR}/Doxygen.cmake")
 include("${ProjectOptions_SRC_DIR}/StaticAnalyzers.cmake")
 include("${ProjectOptions_SRC_DIR}/VCEnvironment.cmake")
 include("${ProjectOptions_SRC_DIR}/MinGW.cmake")
+include("${ProjectOptions_SRC_DIR}/Clang.cmake")
 include("${ProjectOptions_SRC_DIR}/DetectCompiler.cmake")
 include("${ProjectOptions_SRC_DIR}/CrossCompiler.cmake")
 include("${ProjectOptions_SRC_DIR}/DynamicProjectOptions.cmake")

src/Vcpkg.cmake

@@ -232,6 +232,7 @@ macro(run_vcpkg)
   _checkout_vcpkg_repository()
 
   configure_mingw_vcpkg()
+  # configure_clang_vcpkg()
 
   # add the vcpkg toolchain
   _add_vcpkg_toolchain()