Use Modern CMake features instead of CMAKE_CXX_FLAGS (#24861)

* Convert C++ standard settings and warning options from CMAKE_<LANG>_FLAGS to Modern CMake isms.

* More $<COMPILE_LANGUAGE> generator expressions instead of CMAKE_CXX_FLAGS.

* Use $<COMPILE_LANGUAGE:CXX> for all -fpermissive usage

* Fix generator expression that generates multiple flags

* Fix invalid use of CMAKE_CXX_FLAGS instead of CMAKE_C_FLAGS.

* Treat AppleClang as though it is Clang (match pre-3.0 behavior).

* Update our build system to understand that AppleClang is distinct from Clang and remove CMP0025 policy setting.

* PR Feedback.

9 files changed, 13 insertions, 13 deletions

diff --git a/src/ToolBox/SOS/Strike/CMakeLists.txt b/src/ToolBox/SOS/Strike/CMakeLists.txt
index 8e0218a341..7047e3291c 100644
--- a/src/ToolBox/SOS/Strike/CMakeLists.txt
+++ b/src/ToolBox/SOS/Strike/CMakeLists.txt
@@ -106,10 +106,10 @@ if(WIN32)
   )
 else(WIN32)
   add_definitions(-DPAL_STDCPP_COMPAT=1)
-  if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+  if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     add_compile_options(-Wno-null-arithmetic)
   elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-conversion-null")
+    add_compile_options($<$<COMPILE_LANGUAGE:CXX>:-Wno-conversion-null>)
     add_compile_options(-Wno-pointer-arith)
   endif()
   add_compile_options(-Wno-format)
diff --git a/src/ToolBox/SOS/lldbplugin/CMakeLists.txt b/src/ToolBox/SOS/lldbplugin/CMakeLists.txt
index 0e4d40a706..2b65f52cba 100644
--- a/src/ToolBox/SOS/lldbplugin/CMakeLists.txt
+++ b/src/ToolBox/SOS/lldbplugin/CMakeLists.txt
@@ -124,7 +124,7 @@ endif()
 
 message(STATUS "LLDB_H: ${LLDB_H}")
 
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-delete-non-virtual-dtor")
+add_compile_options($<$<COMPILE_LANGUAGE:CXX>:-Wno-delete-non-virtual-dtor>)
 
 include_directories(inc)
 include_directories("${LLDB_H}")
diff --git a/src/dlls/mscorpe/CMakeLists.txt b/src/dlls/mscorpe/CMakeLists.txt
index 43deb47ec9..6a8919326b 100644
--- a/src/dlls/mscorpe/CMakeLists.txt
+++ b/src/dlls/mscorpe/CMakeLists.txt
@@ -10,7 +10,7 @@ set(MSCORPE_SOURCES
 )
 
 if(NOT WIN32)
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-delete-non-virtual-dtor")
+  add_compile_options($<$<COMPILE_LANGUAGE:CXX>:-Wno-delete-non-virtual-dtor>)
 endif()
 
 add_library_clr(mscorpe STATIC
diff --git a/src/ilasm/CMakeLists.txt b/src/ilasm/CMakeLists.txt
index 3d1a74dae6..f780dcae11 100644
--- a/src/ilasm/CMakeLists.txt
+++ b/src/ilasm/CMakeLists.txt
@@ -51,7 +51,7 @@ if(CLR_CMAKE_PLATFORM_UNIX)
   # Need generate a right form of asmparse.cpp to avoid the following options.
   # Clang also produces a bad-codegen on this prebuilt file with optimization.
   # https://github.com/dotnet/coreclr/issues/2305
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-delete-non-virtual-dtor -Wno-register")
+  add_compile_options("$<$<COMPILE_LANGUAGE:CXX>:-Wno-delete-non-virtual-dtor;-Wno-register>")
   add_compile_options(-Wno-array-bounds)
   add_compile_options(-Wno-unused-label)
   set_source_files_properties( prebuilt/asmparse.cpp PROPERTIES COMPILE_FLAGS "-O0" )
diff --git a/src/inc/CMakeLists.txt b/src/inc/CMakeLists.txt
index 517ea8e0f4..c38d59587a 100644
--- a/src/inc/CMakeLists.txt
+++ b/src/inc/CMakeLists.txt
@@ -49,7 +49,7 @@ else()
 
 # The prebuilt files contain extra '!_MIDL_USE_GUIDDEF_' after the #endif, but not in the comment.
 # In order to not to have to modify these prebuilt files, we disable the extra tokens warning.
-if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
 add_compile_options(-Wno-extra-tokens)
 elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
 add_compile_options(-Wno-endif-labels)
diff --git a/src/jit/CMakeLists.txt b/src/jit/CMakeLists.txt
index 5e7c9c50d2..8a3475605b 100644
--- a/src/jit/CMakeLists.txt
+++ b/src/jit/CMakeLists.txt
@@ -4,7 +4,7 @@ include_directories("./jitstd")
 include_directories("../inc")
 
 if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fpermissive")
+  add_compile_options($<$<COMPILE_LANGUAGE:CXX>:-fpermissive>)
   add_compile_options(-Wno-error)
 endif()
 
diff --git a/src/pal/src/libunwind/src/CMakeLists.txt b/src/pal/src/libunwind/src/CMakeLists.txt
index b29e7ee9a2..93b4daf3a6 100644
--- a/src/pal/src/libunwind/src/CMakeLists.txt
+++ b/src/pal/src/libunwind/src/CMakeLists.txt
@@ -22,7 +22,7 @@ add_definitions("-Ddwarf_search_unwind_table_int=UNW_OBJ(dwarf_search_unwind_tab
 # Disable warning due to incorrect format specifier in debugging printf via the Debug macro
 add_compile_options(-Wno-format)
 
-if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
   add_compile_options(-Wno-header-guard)
 elseif()
   add_compile_options(-Wno-unused-value)
@@ -33,7 +33,7 @@ if(CLR_CMAKE_PLATFORM_ARCH_ARM)
     add_definitions("-Darm_search_unwind_table=UNW_OBJ(arm_search_unwind_table)")
     # Disable warning in asm: use of SP or PC in the list is deprecated
     add_compile_options(-Wno-inline-asm)
-    if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
         # Disable warning due to labs function called on unsigned argument
         add_compile_options(-Wno-absolute-value)
     endif()
@@ -48,7 +48,7 @@ if(CLR_CMAKE_PLATFORM_ARCH_ARM)
     # the include/tdep-arm to include directories
     include_directories(../include/tdep-arm)
 elseif(CLR_CMAKE_PLATFORM_ARCH_ARM64)
-    if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
         # Disable warning due to labs function called on unsigned argument
         add_compile_options(-Wno-absolute-value)
     endif()
diff --git a/src/pal/tests/CMakeLists.txt b/src/pal/tests/CMakeLists.txt
index 5597922f72..0ec630df8c 100644
--- a/src/pal/tests/CMakeLists.txt
+++ b/src/pal/tests/CMakeLists.txt
@@ -32,7 +32,7 @@ endif()
 
 # C++ emits errors and warnings for c-string literal fed into char* parameter
 # this is just to take care of the warnings
-if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
   add_compile_options(-Wno-writable-strings)
 elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
   add_compile_options(-Wno-write-strings)
diff --git a/src/pal/tests/palsuite/CMakeLists.txt b/src/pal/tests/palsuite/CMakeLists.txt
index 6726165caf..00a4301784 100644
--- a/src/pal/tests/palsuite/CMakeLists.txt
+++ b/src/pal/tests/palsuite/CMakeLists.txt
@@ -14,13 +14,13 @@ endif()
 
 list(APPEND COMMON_TEST_LIBRARIES coreclrpal)
 
-if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
   add_compile_options(-Wno-incompatible-pointer-types-discards-qualifiers)
   add_compile_options(-Wno-int-to-void-pointer-cast)
 elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
   add_compile_options(-Wno-sign-compare)
   add_compile_options(-Wno-narrowing)
-  SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fpermissive" )
+  add_compile_options($<$<COMPILE_LANGUAGE:CXX>:-fpermissive>)
   add_compile_options(-Wno-int-to-pointer-cast)
 endif()