Relax Clang frontend variant detection

This allows Clang frontend variant detection to work better in more
scenarios such as when compiling with cross-compilers with platform
prefixes.

2 files changed, 25 insertions, 16 deletions

diff --git a/c/CMakeLists.txt b/c/CMakeLists.txt
index e999345..0bb972e 100644
--- a/c/CMakeLists.txt
+++ b/c/CMakeLists.txt
@@ -23,6 +23,7 @@ option(BLAKE3_FETCH_TBB "Allow fetching oneTBB from GitHub if not found on syste
 include(CTest)
 include(FeatureSummary)
 include(GNUInstallDirs)
+include(BLAKE3/Utils)
 
 add_subdirectory(dependencies)
 
@@ -263,32 +264,19 @@ if(BLAKE3_USE_TBB)
     set(APPEND BLAKE3_CXX_STANDARD_FLAGS_GNU -std=c++20)
     set(APPEND BLAKE3_CXX_STANDARD_FLAGS_MSVC /std:c++20)
   endif()
+
   set(BLAKE3_CXXFLAGS_GNU "-fno-exceptions;-fno-rtti;${BLAKE3_CXX_STANDARD_FLAGS_GNU}" CACHE STRING "C++ flags used for compiling private BLAKE3 library components with GNU-like compiler frontends.")
   set(BLAKE3_CXXFLAGS_MSVC "/EHs-c-;/GR-;${BLAKE3_CXX_STANDARD_FLAGS_MSVC}" CACHE STRING "C++ flags used for compiling private BLAKE3 library components with MSVC-like compiler frontends.")
-  # Get the C++ compiler name without extension
-  get_filename_component(BLAKE3_CMAKE_CXX_COMPILER_NAME "${CMAKE_CXX_COMPILER}" NAME_WE)
-  # Strip any trailing versioning from the C++ compiler name
-  string(REGEX MATCH "^(clang\\+\\+|clang-cl)" BLAKE3_CMAKE_CXX_COMPILER_NAME "${BLAKE3_CMAKE_CXX_COMPILER_NAME}")
 
-  # TODO: Simplify with CMAKE_CXX_COMPILER_FRONTEND_VARIANT once min CMake version is 3.14.
-  if(CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
-    target_compile_options(blake3 PRIVATE $<$<COMPILE_LANGUAGE:CXX>:${BLAKE3_CXXFLAGS_GNU}>)
-  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-    if(BLAKE3_CMAKE_CXX_COMPILER_NAME STREQUAL "clang++")
-      target_compile_options(blake3 PRIVATE $<$<COMPILE_LANGUAGE:CXX>:${BLAKE3_CXXFLAGS_GNU}>)
-    elseif(BLAKE3_CMAKE_CXX_COMPILER_NAME STREQUAL "clang-cl")
-      target_compile_options(blake3 PRIVATE $<$<COMPILE_LANGUAGE:CXX>:${BLAKE3_CXXFLAGS_MSVC}>)
-    endif()
-  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+  if(BLAKE3_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "GNU")
     target_compile_options(blake3 PRIVATE $<$<COMPILE_LANGUAGE:CXX>:${BLAKE3_CXXFLAGS_GNU}>)
-  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+  elseif(BLAKE3_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "MSVC")
     target_compile_options(blake3 PRIVATE $<$<COMPILE_LANGUAGE:CXX>:${BLAKE3_CXXFLAGS_MSVC}>)
   endif()
 
   # Undefine scratch variables
   unset(BLAKE3_CXX_STANDARD_FLAGS_GNU)
   unset(BLAKE3_CXX_STANDARD_FLAGS_MSVC)
-  unset(BLAKE3_CMAKE_CXX_COMPILER_NAME)
   unset(BLAKE3_CXXFLAGS_GNU)
   unset(BLAKE3_CXXFLAGS_MSVC)
 endif()
diff --git a/c/cmake/BLAKE3/Utils.cmake b/c/cmake/BLAKE3/Utils.cmake
new file mode 100644
index 0000000..7cadf84
--- /dev/null
+++ b/c/cmake/BLAKE3/Utils.cmake
@@ -0,0 +1,21 @@
+if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.10)
+  include_guard(GLOBAL)
+endif()
+
+if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.14)
+  set(BLAKE3_CXX_COMPILER_FRONTEND_VARIANT ${CMAKE_CXX_COMPILER_FRONTEND_VARIANT})
+else()
+  # Get the C++ compiler name without extension
+  get_filename_component(BLAKE3_CMAKE_CXX_COMPILER_NAME "${CMAKE_CXX_COMPILER}" NAME_WE)
+  # Strip any trailing versioning from the C++ compiler name
+  string(REGEX MATCH "^.*(clang\\+\\+|clang-cl)" BLAKE3_CMAKE_CXX_COMPILER_NAME "${BLAKE3_CMAKE_CXX_COMPILER_NAME}")
+  # Guess the frontend variant from the C++ compiler name
+  if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND BLAKE3_CMAKE_CXX_COMPILER_NAME STREQUAL "clang-cl")
+    set(BLAKE3_CXX_COMPILER_FRONTEND_VARIANT "MSVC")
+  elseif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+    set(BLAKE3_CXX_COMPILER_FRONTEND_VARIANT "MSVC")
+  else()
+    set(BLAKE3_CXX_COMPILER_FRONTEND_VARIANT "GNU")
+  endif()
+  unset(BLAKE3_CMAKE_CXX_COMPILER_NAME)
+endif()